Modern Mechanix, May 1938

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A “US. NEEDS PLANES ANB MEN” — GENERAL ARNOLD - he A FAWCETT PUBLIC ATION. Peers ie ERS n m Apa gees PaaS : ; A $ 2 ; : Q SEE PAGE 72- AAA he -e ae NI ONY SZIGSGH XINWHIAW NYITOK

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NEW KIND OF TIRE GIVES THE 2U/CA257 NON-SKID STOPS YOUVE EVER SEEN! ANNAA Tithe Here’ s the Evidence fiom America’s Largest Independent Testing Laboratory Ss Wins Hands Down in Com, tave Road : “Bo regular, and also the premium- priced tires of America’s six largest tire manufacturers were submitted to a series of exhaustive road tests made over a three months’ period by us, to determine their resistance to skidding and wear, with the following results: “NON-SKID—The new Goodrich Sil- vertown with the Life-Saver Tread gave greater skid resistance than any other tire tested, including those tires listed at from 40% to 70% higher in price. “MILEAGE—The Goodrich Silvertown gave more non-skid mileage than any of the other tires tested in its own price range—ayveraged 19.1% more miles be- Tests by Famous Testing Laboratery GAIN Goodrich makes tire history! With a new Goodrich Silvertown that is really wo great tires in one! For znside the tire is Golden Ply protection against high-speed klow-outs. And oztside is the new Life-Saver Tread that, in exhaustive road tests by the impartial Pittsburgh Testing Laboratory, gave “‘great- er skid resistance than any other tire tested.” E Aes we This tread is actually a road dryer! Its never-ending spiral bars, acting like a battery of windshield wipers, fore the tires wore smooth. Bea sweep water from under the tire, force it out through “BLOW-OUT PROTECTION—Despite |24| the deep drainage grooves—make a dry track for the the severe nature of these tests, no Silvertown blew out, or failed from any cause, while two tires of £ other makes failed.” cg re rubber to grip. eh Seay] No Extra Cost! Go to your Goodrich dealer or Goodrich Silvertown Store for a free demonstration. Remember, this new skid-protected Goodrich Silvertown also has the famous Golden Ply protection against blow-outs. So you get zwo great life-saving features—AT NO EXTRA BOA W NN R k RR SS COST!—to say nothing of 19.1% greater non-skid tire = mileage—which means you get EVERY 6TH MILE FREE! Peyj Goodrich SAFETY Silvertown SKID PROTECTION OF LIFE-SAVER TREAD @%2@ GOLDEN PLY BLOW-OUT PROTECTION

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210 tn basek-.i, either you hit the bati or you di ‘the record speaks for itself! Whether you é realized it or not, the same is true on any =the record speaks for itself] And t wa: you hit the ball on your job, and the measure by which your boss com- pares you with other men, is—most likely —training. The home runs go to those who 400 231 know how to hit them. Many of the job home-run hitters today got their starts by spare-time study of Internatignal Corre- spondence Schools Courses. This coupon is your invitation to follow in their footsteps. Why not mark the subject that interests you most—and mail the coupon today? It may be a big step in your lifel INTERNATIONAL CORRESPONDENCE SCHOOLS 7 BOX 2318-Q, * Why,” and full TECHNICAL AND I Sheet-Metal Worker Z Boilermaker Z Telegraph Engineer Z Telephone Work O Radio Z Mechanical Engineering © Mechanical Draftsman O Machinist O Toolmaker O Patternmaker 5 Diesel engines J Aviation Engines Z Automobile Mechanic O Commercial Refrigeration D Architect D Architectural Draftaman D Building’ Estimating O Contractor and Builder D Structural Draftsman O Structural Engineer U Management of Inventions G Electrical Engineer O Electric Lighting D Welding, Electric and Gas D Reading Shop Blueprints O Heat Treatment of Metals D Business Management O Industrial Management D Trafic Management O Accountancy O Cost Accountant OC. P. Accountant © Bookkeeping J Secretarial Work J Spanish I French Z Salesmanship I Advertising SCRANTON, PENNA. Without cost or obligation, please send me a copy of your booklet, “Who Wins and particulars about the subject before which I have ’marked X: * INDUSTRIAL COURSES Z Plumbing Oi Steam Fitting 2 Meating O Ventilation J Air Conditioning and Cooling J Steam Engineer O Steam Electric Engineer D Marine Engineer O R. R. Locomotives O R, R. Section Foreman U Air Brakes OR. R. Signalmen O Highway Engineering O Civil Engineering O Surveying and Mapping ’ BUSINESS TRAINING COURSES O Service Station Salesmanship O First Year College Subjects O Business Correspondence O Stenography and Typing O Civil Service Mail Carrier O Railway Mail Clerk DOMESTIC SCIENCE COURSES O Home Dressmaking 2 Advanced Dresamaking O Professional Dreesmaking and Designing » CRY. eee Pe If you reside. . ân Canada, J Millinery O Bridge Engineer O Bridge and Building Foreman G Chemistry O Pharmacy D Coal Mining © Mine Foreman O Navigation O Cotton Manufacturing O Woolen Manufacturing OD Agriculture G Fruit Growing O Poultry Farming D Fire Bosses O Grade School Subjecta O High School Subjects gJ College Preparatory O Illustrating O Cartooning D Lettering Show Cards D Signe D Foods and Cookery O Tea Room and Cafeteria Management, Catering “send ‘this. ‘coupon to the International Correspondence Schools Canadian, Limited, Montreal, “Ganada When Answering Advertisements Please Mention May Modern Mechanix

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wie, MODERN MAY ss MORENO = IN CANADA Number 1 Circulation over 250,000 Copyright 1938 by Fawcett Publications, Inc. Next Month— A BIG Your Newspaper By Radio! - - . - - 35 SURPRISE! New York World’s Fair Takes Shape- - - 38 When you go to the news- stand next month you will find a bigger, better magazine bear- SPECIAL FEATURES U.S. Needs Planes And Men - - - - = 42 ing a new titl—MECHANIX ILLUSTRATED. This will be By Brigadier General H. H. Arnold, your old friend MODERN Assistant Chief of the Air Corps, U. S. Army MECHANIX in new, modern- ized dress, with color-photog- raphy cover. The Biggest Little Show On Earth - 48 MECHANIX ILLUSTRATED By Robert M. Hyatt will contain more pages, more and bigger pictures, more human-interest feature articles, The Men Behind The Stop Watch - 58 more home-workshop and hobby projects, more and By Maxwell Reid Grant bigger plans and drawings. Pass the good news on to your friends and tell your news- Tuning Up The Outboard Motor -+ =- - =- 68 dealer to reserve a copy for you. The price remains 15 cents —the biggest bargain on the Pursuing The Postmark - - - =- + =- 70 market! By Montgomery Mulford The new MECHANIX IL LUSTRATED will be out May 10. How To Cut Sections For Your Microscope - 84 LOOK e OR - By Julian D. Corrington, Ph.D. i (Continued on page 8) Pubilshed monthly by Fawcett Publications, Inc., 14th St., & Broadway, Louisville, Ky., U. S. A. Business office, 22 West Putnam Arve., Greenwich, Conn, Entered as second- class matter under the Act of March 3, 1879, at the post office in Louisville, Ky., with additional entry at Greenwich, Conn, Editorial offices: 1501 Broadway, New York, N. Y. Not responsible for unsolicited manuscripts, In U. 8. and Possessions and in Canada, lic a copy; $1.50 a year. Send subscriptions to Greenwich, Conn., address, Other Postal Unions, $2.00 a year, East Indian Agent, P. C. Eranee ‘sons, Bombay, Indla. Printed in U. S. A, Advertising forms close the. first of second month preceding date of Issue. Advertising offices: New York, 1501 Broadway; Chicago, 860 N. Michigan Ave.; San Francisco, Simpson-Reilly, 1014 Russ Bldg.; Los Angeles, Simpson-Reilly, Garfield Bldg. Member Audit Bureau of Clreulation, W. H. FAWCETT, Publisher RALPH DAIGH, Managing Editor ROBERT HERTZBERG, Editor AL ALLARD, Art Director JOHN L. SCHERER, CLIFFORD PETERS, Associate Editors S. S. RABL, Navat Consultant 4

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How Big Is YOUR PAY-CHECK? If you earn under *3,000, Higher Accountancy may be the answer for you s HE size of my pay-check? What business is it of yours?” Perhaps that’s the first reply that comes to your mind. But—stop a moment. It really 7s our business—to help men just like you. In fact, it’s been our business here at LaSalle for 30 years. If your pay-check isn’t all that you’d like it to be, why not consider accountancy? Why not become a member of this well-paid and respected field? Why not, in short, prepare yourself to eam real money—insure a good home for your family—a new car—an education for the growing youngsters—a bank account for a rainy day . . . these and many more of the precious things in life? Maybe you’re one of those ever hoping for “breaks” that will give you a higher standard of living. Yet that’s precisely what most of 30,000,000 other em- ployees in this country are doing. Not all of them, of course. Here and there you find ambitious men who aren’t depending on luck to carry them ahead. They’re following a tested path to increased earnings—leaving nothing to mere chance. They’re iraining themselves for better jobs —every week spending a few hours in serious but interesting study at home. Some day, as expert bookkeepers and later as accountants, these determined men will have stand- ing and a considerably larger income—in a profes- sion that pays and pays well. Why don’t you do as they are doing—take ad- vantage of LaSalle training? Even though you do not know the fundamentals of bookkeeping now— you nevertheless have an excellent opportunity to master accountancy. Many others have done it! Perhaps you’re asking yourself, ““But don’t these others possess natural ability that I lack? Don’t I need a special talent for all this?” Ask rather, “If I do my part, won’t J get results, too?” You will! For all it takes is in- telligence, serious study and work —not genius. Under the LaSalle Ifystem you solve problems by sim- ple steps . . . from day to day, as an expert accountant does. You ing, Auditing, Cost Accounting, Business Law, Organization, Management and Finance. The train- ing—complete and intensive all the way—takes you right into C.P.A. coaching if you desire. Later, when you’re an accountant, it may be possible to go into business for yourself as a public accountant and be independent. Or, if you choose to work for someone else as an executive accountant, it well may be for a salary several times that which you draw now. Write for this FREE book If you’re tired of pinching pennies, investigate ac- countancy and LaSalle training. There isn’t a faster, less expensive or more convenient method to master accountancy. Fill in the coupon and mail. We’ll send you our 64-page book, ‘‘Accountancy, The Profession That Pays.” Then, when you read all the facts, you yourself will be able to judge best whether you have the will to study and apply your best efforts—toward a more secure future. Pes esses see eee eee eee eee LASALLE EXTENSION Adult Business Training Dept. 5493-HR Chicago, IIL use the same basic principles. And when these problems become diffi- cult and puzzle you, you get counsel that could be matched only through I want to earn a bigger salary—through accountancy training. Send me, without cost or obligation, your 64-page book, “Accoun- tancy, The Profession That Pays.” personal coaching by a battery of NaMe earar enearo te aeii ehna ad sear ees SS experts in a big accounting house, In a comparatively short time, Present Position... .. Afe cerugyaris you train yourself in Elements of Accounting, Principles of Account- Addressee ra saa Sask Sere i eae CRY seas caesa iene When Answering Advertisements Please Mention May Modern Mechanix 5

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A frank man to PATENTS-INVENTIONS HE world of invention moves on. About a hundred years ago people were saying, “There’s nothing left to invent”—today we know that is one of the funniest things ever said. Just think what has happened in the last hundred years! Autos, radios, airplanes, and thousands of useful, practical devices for home, shop and office have been invented and put on the market. Inventors are con- stantly making the world a better place to live in. Did you see a notice in the paper that an obscure worker, Hans Wach, has invented a simple device to utilize exhaust steam on steam boats. Already, the report states, the steam ship lines have saved more than $15,000 in fuel bills with his invention. Almost in the same breath the Dept. of Commerce announces that it will soon test out a new non- crashable aeroplane, which the average man can learn to fly in a day, which will travel at 110 miles an hour and sell at the price of a cheap automobile. An unknown Seattle man has invented a robot to go 5,000 feet under the sea and recover millions and millions of dollars worth of gold lying at the Who Are Inventors? You'd be amazed at the men we con- taet in the course of a busy year. Most of them do not consider themselves inventors at all. During their work or leisure they get an idea. They work it out on paper, They get Can You Answer These Questions? Ask yourself these questions: the Patent Laws protect me? What easy steps can I take. without cost, to put myself in position to support my belief that I am the first man to think of my invention? Is a Patent bottom of the ocean since the days of the early Spaniards, f Remember this: For every outstanding big inven- tion there are thousands of small, simple things for use in the home, the office, the factory, on the farm, on every sort of travel conveyance. Little articles like you find on the counters of a 10-cent iore: hardware store, drug store, toy and novelty shop. Many Little ideas Have Big Commercial Possibilities A person finds something he’s using doesn’t work right, or it’s clumsy, or costs too much, He gets a happy thought. He improves the old Article. That’s contribution to human progress. That’s the way that many, many men have reached the goal of financial comfort, independence and even wealth. Most of thè things millions of us use didn’t come from the brains of engineers and physicists. They came from the mind and maybe the crude home work bench of Mr. Average Man, busily engaged in earning his bread and butter at whatever chance or circumstance has given him to do. The “little” man’s opportunity as an inventor was never greater than it is today. Our Business Is To Help You. Write Us Today For more than forty years, this firm has been helping men with an inventive turn of mind. We maintain a large staf of trained, expetienced speclalists—Registered Patent Attorneys, Draftsmen, and Searchers to help How do in touch with us about Protection. worth the cost? Do I need our clients secure all the protection to which Did you know that a dentist a model? Should I try to they are entitled. Fees are reasonable. De- invented the stock ticker, a sell my invention before I ferred payments frequently arranged. Ques- school teacher the telephone, a Parmer the typewriter, an artist the telegraph? Did you know that the crinkly hair pin—sold by millions now—came about because a husband saw his have any te secure financial help? If I do apply how shall I reach people who can market my invention? Can I protect and tions promptly answered. Write us frankly with absolute assurance that what you say will be treated with strictest secrecy. But FIRST, send for the FREE BOOKS shown on the op- posite nage. They are filled with facts, pıc- tures and suggestions. They tell you things it Patented? Is there safe, business-like way for a Patent wife twisting the old-fashioned straight hair pin to make it stay in place? Poor men who have no thought of invention now will be financially well-fixed in a few years because cf a happy thought that the world could use to advantage. sell an improvement on some invention that has already been patented? These are but a few of the questions which usually confront the average man, You need the answers! YOU CAN HAVE THEM, without cost, trouble, or delay. about Patents, Inventions and Selling Inven- tions that we have learned in our long experience. They may save you time, expense, EVEN LATER DISAPPOINTMENT. Simply fill in the coupon. No charge, no obligation. Write us today. 6 Accept No Substitutes! Alceays Insist on the Advertised Brand!

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man talk about “SELLING INVENTIONS [] 115 Mechanical Move- ; i ments Like These 3 R E f Besides many other features and facts there are 115 differ- . ent mechanical movements and B 0 0 KS principles in the big, 48-page is Book below. Maybe there is with just the idea you need to solve some mechanical problem. Use 6 8 PAG E S the coupon or write us a card or letter. of Fa C £s d Pictures! | Pictures! About Selling NEW saat 3 wW A EVAN S &r C O. ENA INVENTIONS REGISTERED PATENT ATTORNEYS i MAIN OFFICE: 30-E, VICTOR BUILDING, y So far as we know, the WASHINGTON, D. C, facts in this booklet have Other Offices: 2610-B, Singer Bldg., New ae never before been pub- 1445-B, Monadnock Bldg., Chicago . 1010-B, Hobart Bldg., San Francisco lished by any Patent At- 405-B, Garfield Bldg., Los Angeles torney. You are given Send me FREE copies of your books, “Patent Protection” and very definite suggestions “When and How to Sell an Invention.” (Note: Same books sup- on “When and How Plicd by any of branch offices listed abore.) to Sell an Inven- tion.” It also comes Giy or TO cs westne da pvsnlew a nivar raresa State... ....- eee | When Answering Advertisements Please Mention May Modern Mechanix 7

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U. S. M f t a esire men t learn Piec ric Are We ing and ge anuracturers Practical experience under actual production conditions In the laboratories of the School of Engineering. Moderate training Fee. Accepted applicants wll? be fully trained until ready to pass rigid test and assisted in securing employment, ARC WELDING Weldin; work, ie and miss_jobs and low become a trained Speciallst in MILWAUKEE ome 6 CHO of ENGINEERING Sustitute of Efectrotechnics 538-MM North Broadway and E, State, Milwaukee, Wis. Desovecoooosopeoteottooovosovoosovetootoosocossotoovoessosot: Without obligation send Free Booklet ‘The Dawn of a Gigantic Industry and Its Outstanding -Dpportunities:’ Also tell me how to become Welding Operator (3 mo.)_-.. Gas Welder (6 wits.)-------- Welding Technician (6 mo.)_. Welding Engineer (1 yr.)_--- Electrical Engineer B. S. Degree (4 yrs.)_---... Student Loan Plan_.- Refrigeration and Alr Condi- tioning Techniclan (3 mo.) Radio, Television (6 mo. Commercial Radio Engineer (1 yr.) Earn Part Expense Plan. MAKE MONEY IN YOUR WORKSHOP. Build furniture, auto trailers, canoes, iceboats, cruisers, sailboats and electric refrigerators described in VEPRINT BOOKL R ET MODERN MECHANIX PUBL, CO., Fawcett Bldg., Greenwich, Conn. 7° [M GOING TO HAVE AN ATLAS tL My Sde Free NEW CATALOG All who see the Atlas preciston lathes and other shop equipment talk about the power, versatility, and extra features of these mod- ern machine tools, See for your- self before you buy, Send for new 1936 Catalog today. ATLAS PRESS Co. 552 N. Pitcher Street Kalamazoo, Mich. CONTENTS—Continued from page 4 SHORTER FEATURES | Modelers Display Craft - - - =- - - - 54 Behind The Scenes At A Museum - - - 64 MODERN PHOTOGRAPHY SECTION Winners Of Photo Awards - - - - - - 103 The “Tin Can Special” Enlarger - - - - 104 Filter Facts and Factors - - - - - - 107 Kinks For Camera Fans - - - - - -~ 110 _| Portable Safelight - - - - - - - - - 112 ‘Developer Heaters - - - - =- - - -112 ‘Novel Mirror Picture Frame - - - - -ii Glassless Negative Holder - - - - - -113 Developing Outfit For Cut Film - - - - 114 Amateur Photo Puzzlers- =- =- - - - - 116 HOW-TO-BUILD FEATURES A Wrought Iron Globe Light - - - - - TI This Sidewalk Runabout Is Easy To Build - 72 Test Your Model Airplanes : In This Wind Tunnel - - = %6 Build A Jifly Ski = 5 aa s s = - 80 A Model Airplane Jig Saw - - - - - - 8l Construct A Small Gate Leg Table - - - 82 A Home-Made Drag Saw - - - - - - 87 Cigarette Box Has Trick Lid - - - -'- G1 A Utility Table For The Auto - - - - - $8 FOR THE WORKSHOP FAN Handy Wire Brush Wringer Eits Any Paint Can - - = = - = = = 18 Handy Kinks For Star Drills - - - - - 7 Handy Sandpaper Files - - - - - - - 79 Choose The Right Brush - - - - - - 94 RADIO AND ELECTRICITY Device Shows Bus Location - - - - =- 5I New Ultra-Violet Ray Source - - - - - 65 How To Reduce Hum In Radio Receivers - 100 Shielded Lead- sa Gives Peduction, in Noise Level - - - - 100 A Fused Line Filter - = - = - - - - i301 Meter Tests Reading Light - - - - - - 102 AUTOMOTIVE Auto Courtesy Light Devised - - - - - 62 Hand Meter Tests Headlights - - - - - 67 Short Cuts For The Motorist - - - - - 99 AVIATION Model Plane To Serve As Target For Ar- tillerymen - =~ - - - - 52 Aero Experts Praise Diesels --- = = 62 Constructs Novel Altimeter - - - - - 66 (Continued on page 10] 8 Accept No Substitutes! Always Insist on the Advertised Brand!

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Animals To Supply Heat In Air-Conditioned Barn IR-CONDITIONING, coupled in America’s mind with big cities, big theaters and luxu- rious private homes, can be expected to invade the farm shortly to make the farmer’s barn a better place to work in and a more healthful place for livestock to live in. But when it does invade agriculture, air-con- ditioning will not always use the apparatus ' utilized in the cities. This was indicated in an article by F, L. Fairbanks in the current issue of Agricultural Engineering. A mechanical heating unit or a mechanical cooling unit is not always strictly necessary to air-condition a barn where livestock are kept, Mr. Fairbanks reveals. Animal heat, good in- sulation and proper ventilation are frequently the only ingredients necessary to control the atmosphere in which farmers must work and livestock must live. Some of the equipment can be made from materials found on any farm. Air-conditioning for barns and storage cellars and buildings are discussed by the agricultural engineer.. The problem of storage conditioning is made relatively simple by the fact that no air flow is needed. In fact, he remarks, except for the occasions on which the storage space should be aired, any air flow is actually undesirable. A large amount of the heat required in winter can come from the bodies of the animals them- selves, provided the insulation is effective enough to retain that heat within the building, Mr. Fair- banks explains. A trough near an opening in the roof can be used to take advantage of the relative flow of hot and cold masses of air to circulate clean air through the building. Back of the scheme de- scribed by Mr. Fairbanks is the fact that winds come from the same relative motion of hot and cold masses of gas in the earth’s atmosphere. Defective Welds Detected By “Magnetic Eye” A “magnetic eye” which can see into metals and detect bad welds has been developed by Pro- fessor W. B. Kouwenhoven of Johns Hopkins University and A. E. Vivell of Princeton Uni- versity. The “eye” is based on principles of magnetism. The welded seam is magnetized by a powerful alternating magnetomotive force. For welds less than one-quarter-inch thick, 60 cycle current in- sures penetration of the magnetic flux. Two search coils connected in opposition are placed on the seam so that any stray field which may be present cuts their windings. The shape of the wave of electromotive force induced in the coils is then observed by means of an oscillograph. Get aoa Kick — p“ me Motoreycling is the world’s greatest outdoor sport! Good times all the time for the owner of a Harley- Davidson. Ride with the happy members of your local motorcycle club. Go on gypsy tours, reliabil- ity runs, tourist trophy races; take in hillelimbs, Tace meets and other thrilling events. See the classy 1938 models at your Harley-Davidson dealer, Ask about his Easy Pay Plans—mail coupon NOW! E HARLEY-DAVIDSON MOTOR CO, | Dept. MM-538, Milwaukee, Wis, B Tm rarin’ to be a rider, Send FREE motorcycling E magazine, ‘The Enthusiast” and illustrated literature. | Stamp is enclosed to corer postage, ll BR Name---------------------2- Address. il E aana ran e man y age is 3-19 years, ( ) 20-30 years, ( ) 31 years E ana up, ( ) under 16 years. Check your age group, When Answering Advertisements Please Mention May Modern Mechanix 9

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A GOOD PAY JOB IN ON REAL MOTORS, GENERATORS, ETC. PAY TUITION AFTER GRADUATION Practical training on full size Learn about the *‘Pay Tuition electrical equipment.“‘Learnby After Graduation Plan,’ {Part Doing” in 12 short weeks. No Time Employment Plan.’ “Job previous experience oradvanced After Graduation aan ce. education needed. Send the NOW... Diesel, Air Condition- Coupon NOW for Big Free ing and Electric Refrigeration Ilustrated Book. at no extra cost. pannas MAIL THIS COUPON TODAY caea==, H.C, LEWIS, President; COYNF ELECTRICAL SCHOOL 500 S. Paulina St. Dept. 58-53 Chicago, 111. i Please send me your Big Free Book and details of your f “Pay Tuition After Graduation Plan." ] [} Learn Profitable Profession in QO days at Home fs, Salaries of Men and Women in the mee: A fession of Swedish M: er to oben thelr own of- let~They'r THE College or Ra Massage 1601 Warren Bivd., Dept 5358, Chicago (Successor to National Coltege of Massaae) WORKS ON 110-VOLT™S ṢŞ Electric Light CIRCUIT — Atthisunheard of price, youcanget =Œ = this marvelous DYNAMIC Super- -r Charged Welder — this welder is a © radical departurefrom accepted welding prac- tices. It will dothe work of much higher priced types — efficiently cooled —light of weight— easily portable, Will solder and braze on the lightest material, Works on iron, steel, tin, brass, copper and all other metals. WELDS Cylinder Blocks, Bumpers, Fenders, AG E NTS Tanks, Farm Machinery... With this Dynamie Super- Charged W LDER, a man without previous experi- Make big profits ence can make as much as $5.00 on e repair job that can be donein less than one hour. Many welding operators make W as much as $15.00 - $20.00 YY) a day—Go into business— Ñ Open a Welding Shop NOW, DYNAMIC WELDER COMPANY 2226-DF Silverton Road, Chicago, Illinois Write TODAY and ask for our 10-DAY TRIAL OFFER. NI CONTENTS—Continued from page 8 NEW MECHANICAL INVENTIONS Test Chair Gauges Comfort - - - - - 4l Wrist Magnet Is Beauty Aid - - - - - 41 Sun Operates Gas Machine - - - - - - 47 Machine Tests Peas’ Quality - - - - - 52 Simplified Deep-Well Pump Increases Ef- ciency 50% - - - - =- - - - - + 53 Apparatus Breaks Germs With Tonal Waves 55 Ice-Making Unit Mounted On Trailere Type Truck - - - - - - - = 56 New Tool Exerts Pressures Up To 1,500,000 Pounds - - - - 57 “Phonograph” Tests Mentality - - - - - 63 Gasoline Turbine Engine Perfected For Ma- rine Use - - - - - ----- -65 Apparatus Takes Photographs Of Invisible Particles - - ae - - 66 Scale Device Tests Peaches - - - - - - 66 DEPARTMENTS Problems - - - --- = = = - - - 18 Chips From The Editor’s Workbench - - - 28 Nic Sprank’s Oddities - - - = - - '- 34 Crafts And Hobbies - - - - - - - - Tl Photography Section - - - - - - - - 103 New Ideas For Home And Shop - - - - 146 OUTDOOR KINKS Hints For The Fisherman - - - - - - 88 Tips For The Home Gardener - - - - - 92 MISCELLANEOUS False Gems Easily Detected - - - - - 41 Process Reinforces Oil Films - - - - - 41 Mirror Teaches Batting - - - - - - - 47 Hospital Boasts Safety Chute - - - - - 47 Tiny Tea Set Worth $2,000 - - - 52 Night View Of Edison Tower Makes Str striking Photograph - - - 53 Tiny Stage Coach Model Valued At pis - 55 Fooling The Birds- - - - - - - - - 56 Lock Raises Vessel 60 Feet - - - - - - 5I Scientist Secures Photo Of Large Sunspot Group - - - - - - - 62 Working Steam Roller Model Pulls Heavy Load - - = - = - 63 Engineers Pave River Bed - - - - - - 65 Student Develops Explosive - - - - - 67 Miniature Home Features 25 Furnished Rooms -- =. --=-- --- - -6T 10 Accept No Substitutes! Always Insist on the Advertised Brand!

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Steady Work As nearly all manufacturing and building starts on the drafting table, the draftsman is one of the first to be hired, last to be laid off. His blueprints, his specifications, give the final word in what the workmen are to do. Good Pay The draftsman has been called the Junior Engineer, which accurately describes his work, position and pay. He combines knowl- edge of principles, mechanism and construc- tion details with ability to draw plans and indicate methods. Usually his salary is con- siderably above the wages of the mechanic and, of course, less than that of the engincer. Chance for Promotion Helping design new buildings, machines or construction methods, the draftsman knows what his firm is planning or considering. It may be the superintendent—engincer—even the prospective buyer with whom he con- sults. These contacts, plus his experience, place him in an excellent position for promo- tion when next there is a good opening. Young at 40 Athletes, farmers, factory and shop workers — all who rely on ‘muscle often are old at 40. Office workers — executives, teachers, profes- sional men, draftsmen— just approach their prime at 40 to 50. Training increases your value AT ONCE and continues to help boost your earning powcr as you mature, Enjoy a Real Job in Industry Become a Draftsman Don’t Be Just Average What happens to the average man?.Not having thorough training for a worth-while job, he goes along year after year, wish- ing he had a good job, but wishing was never a substitute for training. $40 a week is about his top, usually never that high. Grows old on the job, starts down at 40, finds himself slipping in speed and salary. Security for Yourself and Family Even if you are now only 18, 25 or 30, youshould look ahead —hegin training TODAY for the job you want at 50, Training helps you to be independent—self-supporting. It helps you to mjoy associations denied to untrained men. Training helps you to offer your family advantages far in excess of what you could give them as an untrained man. Investigate NOW. American School, Dept. DD 528, Drexel at 58th, Chicago Modern Mechanix Publishing Co. Make Money In Your Workshop — Free Blueprint Booklet More than 125 plans are listed in the new MM Blueprint Booklet for building your own radio, boats, model railway, electric refrigerator, model planes and scores of other projects. Send stamped-addressed envelope for free copy. Fawcett Bldg., Greenwich, Conn. the job... FRE opportunity for YOU as inger Print Expert, u’d like, salary, Book, low prices. Easy Terms Offer, if 17 or over, Literature will be sent only to persons stating their age. INSTITUTE OF APPLIED SCIENCE 1920 Sunnyside Ave., Dept. 2355, ARREST HIM, OFFICER! I'LL HAVE COMPLETE FACTS ON THE OTHER FELLOW TONIGHT! Secret Service Operator No. FOLLOW HIM through all the excitement of his chase after the counterfeit gang. Write NOW for Confidential Reports No. 38 Made to His Chief! It may open your eyes to the great The kind of xeltement! Travel! ! A REGULAR MONTHLY REWARD MONEY. uates of Lhis school HEAD 47% of all Identification Bureaus in U. S.! Write for Free Reports, Finger Print Chicago, Ill, 38 is on START AT HO ME Here’s your chance—a money-making business of your own. Turn potatoes into cash by making new kind of Poe ips with my Improved outft, elicious, superior, ‘NON: E Chips at low cost. A few hours practice does it. Begin any- where—clty, villagi town. Potatoes cheap and plentiful, Wholesale or re- tail. Steady year ‘raund Groceries e » restaurants, taverns do the retaillng for you. WE HELP START YOU IN BUSINESS Great quantities of Chips are eaten gaily. Profit large—unusually_ so. You can start this money-making business on a “next to nothing” outlay of. cash, Write for Potato Chip_ Booklet, LONG-EAKINS CO., 542-6 High St., Sprinsfield, Ohio a well paid Grad- AUTOPOWER tells you how in plain, easy, simple and illustrated instructions that anyone can follow. Change auto generators into useful, practical A C and D C generators and motors with voltage from 2 to 1,000 volts, for power, light, welding, radio, sound, etc. Generators can’ be driven by wind, No_ previous experience nor speclal tools needed. water, fan belt, ele, INSTRUCTIONS FOR BUILDING AN A C WELDER THAT ACTUALLY WORKS UP TO A 3/16" ROD. PLANTS. ALSO COMPLETE PLANS FOR WIND AND WATER POWER Send for your copy of ‘‘AUTOPOWER.” dorsed by thousands. S$. W. DUNCAN, Publisher Already used and en- 412 S. Hoyne Ave., Chicago Only $1.00 postpald, When Answering Advertisements Please Mention May Modern Mechanix

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Small Danti THAT HAVE BUILT BIG BUSINESSES INVENTIONS do not have to be complicated to be profitable when Pat- ented. The 5c and 10c stores flourish on simple Patented products which are commercially suc- cessful. The zipper, safety pin, thumb tack, paper clip, collar button—all simple, yet familiar inven- tions—brought their inventors rich rewards. If you have a Patentable invention—act to protect it. Many of the most useful, widely popular, greatly profitable, and extremely successful inventions have been very simple ones. You have only to look at the devices we have pictured here to realize how a simple invention may become a utility bought by a hundred thousand or a million people soon after it is produced. Don’t be afraid that the simplicity of your invention makes it valueless. The thing that you find so simple that you wonder why a thousand other people haven't already done it is often the invention worthwhile. HOW OTHER INVENTORS GOT STARTED The list of men who succeeded in in- vention with only a poor boy’s start is a very long and noble one. Poverty, hardships, lack of friends, distance from the market—these could not hold back Bell, Edison, Eastman, McCor- mick, Whitney and others. Everyone cannot succeed. But every man can try. Courage, sacrifice, and hard work may bring you a measure of the success these men had. Lack of mechanical ability is not a serious drawback. You can always get someone able to build a model, draw a detailed design, cr otherwise materialize your invention for you. The big drawback is discour- agement. Your invention of a practical article or an improvement upon an old one should be patented NOW. Frequently many of the thousands of applications filed in the U. S. Patent Office each year are for the same or almost the same invention. In such a case, the burden of proof rests with the last ap- plication filed. Sometimes a delay of even a few days in filing the applica- tion means the total loss of the patent. LOSE NO TIME. The entire time of this large and ex- perienced organization is devoted ex- clusively to patent and trade-mark cases. We know the rules and require- ments of the Patent Office. We under- stand the technicalities of Patent Law. We can proceed in the quickest and safest ways in preparing an application for a patent covering your invention. THE BIOGRAPHY OF GEORGE EASTMAN Views of the man who used Patent Protection to amass millions and give per- fection to a new art—Photography—itself one of the greatest inventions. CLARENCE A.OBRIEN & HYMAN BERMAN 317-C ADAMS BUILDING WASHINGTON, D. C. Registered Patent Attorneys Before U. S. Patent Office 12 Accept No Substitutes! Always Insist on the Advertised Brand!

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If you have an invention that is patentable—and want to secure for yourself your inventor’s sole right to profit from the invention—you can’t afford to lose time in securing the protection of a U. S. Patent. Other inventors may be , working on the same invention right now. Should they develop this invention and file patent application before you do—the burden _of establishing priority will be upon you. Our Big Book—‘Patent Guide for the Inventor”—will tell you the quickest possible way to secure Patent Protection for your invention. The First Important Step in Securing a Patent is to obtain the services of a Regis- tered Patent Attorney. The U. S. Patent Office advises that you secure the aid of an experienced Registered Patent Attorney to prepare your statements, Establish the date of your invention as explained in our book and disclose your invention to him in correct form. He then makes a SEARCH of the Patent Office Records and reports to you on exist- ing U. S. Patents which might bear on your invention, giving his opinion on the advisability of proceeding and filing formal application. Reasonable Fees—Con- venient Terms Don’t worry about finances. Our fees are very reasonable—we can arrange convenient terms of pay- ment. It is our custom to permit clients to pay for our services in in- stallments as the application pro- gresses in our office. See our Big Book for fees in obtaining Patent. It explains our arrangements clearly. Send for it NOW! SEND FOR IT TODAY! FREE RECORD OF INVENTION FORM Use our Free “Record of In- vention” form to assist you in recording the descriptive out- line of your invention and to establish the date of your in- vention, With it you can make a rough sketch of your invention and have it wit- nessed in a matter of value to you as evidence should occasion arise. CLARENCE A. OBRIEN and HYMAN BERMAN (Please write or print plainly) Fl om om ECELLELLLLELCEELCELELLELELLLLLLLTETTTTA i j B i 317-C Adams Building, Washington, D. C. : p Registered Patent Attorneys . A Before U. S. Patent Office : f Please send me at once your Big Free 48-Page Book, “Patent H T Guide for the Inventor” and your Specially Prepared “Record of E i Invention” form. This request does not obligate me, i - Name .. 1 Address E i L | Li I : When Answering Advertisements Please Mention May Modern Mechanix 13

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INRUDE OUTBOARD MOTORS A brand new Evinrude... amazingly light, handy and ; powerful. Literally packed i with big-value features in- ' cluding famed Hooded i Power — Evinrude Co- i Pilot— Underwater Silencing. Starts in- . stantly! — spins into action with a flick of the starting cord. Runs | three hours ona single j | fill—and costs less than 3¢ an hour to oper- ate. Send for catalog! ELTO PAL only $37.50 Elto PAL (built by Evinrude) weighs only 14 pounds, and drives boats at twice the speed of oars, Elto ACE, 347.50 — the husky Handi- twin, only $67.50. Each a stand-out value in its class! FREE CATALOGS! Write for 1938 Evinrude and Elto cata- loga, Boat Directory and Boat- and-Motor Selector, Àl free. Addrees EVINRUDE MOTORS 6468 N. 27th St., Milwaukee. PRICES F, O. B. FACTORY "SENSATIONAL OF F E WOR instruction booklet, only $1.75 postpaid. Two additional fencing swords FREE for limited time. (Regular of foils $3.96.) ORDER NOW. ALL-AMERICAN FENCERS GUILD JO Dept. 5MM mand. acetylene body and fender bumping, spray paint- || ing. 14 MICHIGAN TRADE SCHOOL 3763 Woodward Ave.. E R FENCING sworns EREE N CING T p's FINEST sPpOR a FUN-HARMLESS Develops strong body and alert mind. HARM- LESS. The spring-steel 3-foot-long folls (swords) are equipped with rubher buttons. Aluminum cup-shaped hand guards, Our De Luxe foils are built for hard usage. Complete set of two folls (swords) and free price of these two sets 48 West 48th St., New York, N. Y. = MECHANICS & WELDERS Auto Mechanies and Welders are in big de- Complete courses in are andg welding, metal finishing, § Special low rates. Write today. Detroit. Mich. TION men Southern California, world’s aviation center, needs trained men to build and fly planes. Only trained men accepted. Get quicker, lower-cost training at California Flyers, leading fying- mechanical school in this great aviation center. Secure steady employment, make big money, get the thrill of a red-blooded job in aviation. CALIFORNIA FLYERS LOS ANGELES, CALIF. NSLS LL, Send for California Flyers FREE Book California Flyers, Los Angeles Municipal Airport, Inglewood, Calif. N na HAVE gaw oRNiA M wut? Age State. MM ` a PPO OOO Soo ww wy ww New 100 page book contalns most complete list of woodworking supplies in the world— Standard American woods cul-to-size at bar- gain prices, Rare imported woods, Veneers, plywoods, inlays. carved legs, mouldings, decorations, Hard-lo-find ornamental hardware, scroll saw patterns, wood-finlshing instruc- tlons-How to make Venetian Blinds at 14 Send only 10¢ for Catalog No. store priecs. 10 to Craftsmen's Wood Service Co., 2727 S5. Mary Street, Dept. 4735, Chicago, lll. RAISE POULTRY FOR PROFIT START AT HOME. MARKET WAITING. Garage, Darn or backyard all that is needed. Learn latest methods froin our Home Study Course and put cash in your pockets every day. We train you, help you. Get facts about our unusual offer NOW! Men and women making money in every state—town and coun- iry. Send for illustrated FREE BOOK today! NATIONAL POULTRY INSTITUTE CD Dept. 131-D Adams Center, N. Y. Splendid opportunities. Prepare quickly in spare time. Easy method. No Previous experience necessary, common school education sufficient. Many earn while learning. Send for free booklet ‘Opportunities in Modern Photography t, particulars and requirements. A x RICAN SCHOOL OF PHOTOGRAPHY pasts 3601 Michigan Avenue Dept. 2055 Chicago, Illinois We paid M. M. $1174 for excep lar erop” SNOW-KING mushre free picture hook Lelis if you barn, suitable, We furnish ina all crops through our 25 brane today for "Guaranteed success P by $5000 bond. Est. 1908. UNITED MUSHROOM Co. 3848 Lincoln Ave., Dept. 314, Chicago, MIDGET RACING Get full details on this thrilling Sport: facts for fans. builders and drivers; track sizes ana regulations; car specifications, pictures and working drawings. This book also shows and tells about Indianapolls cars, Miller-Fords — and _ world’s fast cars. AUTOMOBILE RACING, Fourth Edition, $1.00 postpaid, $1.15 C. O. D. RAY F. KUNS, Dent, A-17, Madisonville, Cineinnati, Ohio. Accept No Substitutes! Akcays Insist on the Advertised Brand!

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Device Calibrates Voltage Of Powerful X-ray Machines The super-voltage X-rays used in treating deep-seated cancers can be accurately standard- ized for the first time, the U. S. Bureau of Standards has announced. Measurements up to 400,000 volts have been made for such standard- ization by two scientists of the Bureau’s staff, Dr. Lauriston S. Taylor and George Singer. The significance of the work, Dr. Taylor re- ports, is that it takes the “chance” out of previous work in the field of high-voltage X-ray therapy. Previous experimenters have used 400,000-volt X-ray without knowing, truly, what dosage they were administering. They obtained different results with the higher voltage rays but were unable to know whether the effect was due to the characteristics of the more piercing radiation or to inequalities in X-ray dosage. The new Bureau of Standards work permits dosages of radiation up to 400,000 volts to be known ac- curately for the first time. Previously 275,000 vo'ts was “tops” for such calibration work. To measure the rays, a tube of special design was constructed and one of the world’s largest pressure X-ray ionization chambers (shown above) was built. This research was necessitated by the building and operation, within the last three years, of several dozen X-ray plants operating at the higher voltages. Previously X-rays generated by voltages up to 200,000 volts were used in treat- ing cancer and other serious diseases. It is being predicted that airplanes have reached their top speed, so far as commercial flying is concerned. NOTICE Changes in the make-up and title of this maga- zine will become effective with our next issue. Reserve your copy now. Our new name will be— “MEcHANIX ILLUSTRATED.” ie ie & Start $1260 to $2100 a Year 42,766 APPOINTMENTS IN 1937 GOV'T YEAR Railway Postal Clerks Railway Postal Clerks get $1,900 the first year regular, being paid on the first and fifteenth of each month. ($79.17 each pay day.) Their pay is automatically increased yearly to $2,450. Advance may be had to Chief Clerk at $2,700 a year. ($112.50 each pay day.) 3 Days On—3 Days Off—Full Pay Railway Postal Clerks on long runs usually work 3 days and have 3 days off duty or in the same proportion. During this off duty their pay continues just as though they were working. They travel on a pass when on business, When they grow old, they are retired with a pension, City Mail Carriers, Post Office Clerks Clerks and Carriers now get $1,700 the first year on regular and automatically increase $100 a year to $2,100 and $2,300. : Customs Inspector Salary $2,100 to start. Men 23 to 45. Work connected with examining baggage and merchandise entering the country from foreign parts covering boats, trains, roads, automobiles, etc. Many Other Positions Many other positions are obtainalle. ‘a Customs Those wishing these positions should INSPECTOR qualify at once. Get Free List of Positions Fill out the following coupon, Tear it off and mail it today—now, at once, ë This investment may resull in your getting a big-paid govern- ment job, : — e ee ee ee ee FRANKLIN INSTITUTE, Dept, P262, Rochester, N. Y. Ttush to me, entirely free of charge (1) a full deserlption of U. S. Government Jobs; (2) Free copy of illustrated 32-puge book, ‘‘How to Get a U. S. Government Job; (3) List of U. S. Government Jobs; (4) Tell me what to do to qualify for a U. S. Government Job. ATUTON jes dcsaa nedieie bigs inini eerde Me KEEA Aa Maeda ae. aal ` Use This Coupon Before You Mislay It, Write or Print Plainly. 3 When Answering Advertisements Please Mention May Modern Mechanix 15

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K Cash ror spare TME! MAKE $25 TO $30 PER WEEK AT HOME IN YOUR SPARE TIME THE IDEAL LAWNMOWER SHARPENER Like magic, the Ideal Lawnmower Sharpener makes old, dull, half worn-out mowers cut like new. Simply set the mower In the Ideal and the machine does the rest. Sharpens any lawnmower to a perfect edge in 15 to 20 minutes, usual charge $1.00 to $1.50. Attach to light socket. Start In your basement or garage. Work in spare Lime. Attachments furnished for grinding skates, grass shears, hedge shears, sickles, scythes, axes, cte. FREE CATALOG tells complete story. WHAT THESE MEN DID .. You Can Do Remember, no experience is necessary, Most men sharpen_lawnmowers in spare time only. J. B. Van Dien writes: ‘‘Some weeks I eurned $40 a week with my Ideal just as a side line.” George Seitel writes: * have sharpened over 500 mowers and every customer is well plea: ay Me Larsen writes: ra: oaee 9 moos a day.” Roy F. Stier sa; ‘I live a town of 5 and to-date have sharpened 200 mow at $1.25. Edward A. Mynderse wriles: E “Have sharpened around 500 mowers this season.’ Nick Baltes says: "Last summer I sharpened 200 mowers at 1.00 each.” Bucher Battery Co. write: “We sharpened over GOO mowers last year at $1.50 each.” FREE BOOK Shows how! Right now, before you forget It, send for a copy of oue FREE BOOK, "How Ta Make $25 to $30 per week in SPARE TIME.” SEND POST CARD TO THE FATE—ROOT—HEATH CO. 328 Bell Street, Plymouth, Ohio ss MAKE MONEY IN YOUR WORKSHOP Guild furniture, auto trailers, canoes, iceboats, cruisers, sailboats and electric refrigerators described in FREE BLUEPRINT BOOKLE a MODERN MECHANIX PUBL, Fawcett Bldg., Greenwich, Conn. CO., Areyouadult, alert, ambitious, willing to study? Investigate LAW! We guide you step by step— furnish all texts ,including14-volume Law Libra- ry. Training prepared by leading law professors and given by members of bar. Degree of LL. B. conferred. Low cost, easy terms. Send NOW forFree,64-page “Law Training for Leadership.” LASALLE EXTENSION, Dept. 5493-L, Chicago 1000 USES SUPER-TOOL OF The new WHIZ ELECTRIC TOOL is the $ handiest, most useful pow tool ever made. Not a deli cate instrument but a real rugged tool, equally effec- tive for both power and pre- cision work. Drills through Xa inch iron plate in 42 sec- onds or engraves i i designs on any materi Alloys - Plastics - Glass-Stecl- ete. Saves time. Eliminates tedlous labor, Plug into any socket AC or DC, Chuck 14” capacity. bearing “thrust. Powerful, triple-geared motor. ‘Worth its weight in gold to mechanic or handy man. STANDARD MODEL with Normal Speed (uses 50 differ- ent accessories, Instantly interchangeable) only 86.95. FREE Accessory outfit (Value $2) Includes set of drills, mounted 11" grinder, sand- ing discs, cutting wheels, mounted brush, polishing wheel. cte, FREE with each outfit ordered NOW. We pay postage on all shipments. Will send C.0.D, IF desired, 10 DAY TRIAL—MONEY BACK GUARANTEE. Special **2-SPEED"? MODEL combines Normal Speed and High Speed in one outfit (uses 200 accessories) only $8.95 complete, with above accessories and carving bur FREE. PARAMOUNT PROD, C0., Dept, 5-B, 48 W. 84th St., New York LEJAY WELDER Now Oniy §].00 $1.50 forelgn POSTPAID Complete kit of parts for mak- ing our genuine LeJay Welder which has proved such a sensa- tlon. Thousands sold to satis- fied customers ut $2.50 each, LeTtay now offers this famous tool In kit form at a saving of $1.50. Easy to assemble—no other parts needed, Operates from car. battery. Intense heat welds most metals. Your first repair job will more than pay the small amount you spend for this amazing tool. Send $1.00 for your welder today. | Satisfaction guaranteed or money refunded. We also ship C. O. D. MFG. CO., 314 LeJay Bldg., POSTPAID ANN LE JAY Minneapolis, Minn. SPECIAL Only Correspondence Courses In RADIO and ELECTRICAL ENGINEERING ELECTRICAL ENGINEERING Se, good grasp Prepare yourself, at Low Cost, for secure future. Modern simplified anyone can understand quickly. course. So RADIO ENGINEERING Extra fine course in radic, public address, P photo-electric work. Trains you to be Super-service man, real vacuum tube technician. Experimental kits furnished, Diploma given on completion. Tuition, ONLY $25, either course. Deferred payment plan avaliable. FRE E! Send name quick for free coples of school catalogs = student magazines, complete details. SEND NOW. LINCOLN ENGINEERING SCHOOL, Box 931-77, Lincoln, Nebr. . STOP Backtrackingar= Haven’t you often OLE: ame driven the wrong road ff} and had to backtrack many miles? The Hull Stream- ; line Auto Compass always shows your direc- tion of travel, prevents backtracking, saves money and time for only $2.95 at your dealer, Two-piece model $1.95. Write for circular. HULL MFG. CO., P. O. Box 245-M; WARREN, OHIO RTOON voor way ero SUCCESS / DON’T COPY - LEARN TO ORIGINATE! RAYE BURNS will teach you HOW to CREATE 8 5 ORIGINAL CARTOONS at home that you can ) —~ cal tield, SELL! Course has 26 lessons and 600 illustrations. Send name and address for free details. Only...» RAYE BURNS SCHOOL, Dept. F, Box 2194, Cleveland, Ohlo RUBBER [oW cs MOLDS £ Ot.. Amazing rubber mold-making outfit makes perfect flexible molds of plaques, ash trays book-ends, etc. Molds cost from Ge to 25c cach, Each mold makes hundreds of novellies and gifts to sell up to $1.00 apiece! No experience necessary. Everything: fur- nished. Start profitable business in your home... sell to stores, friends, resorts, road slands ov by mall-NOW! Make BIG MONEY full or spare time. Write for complete FREE details and easy Instruc- tions. SO-LO WORKS, Dept, E-834, Cincinnati, Ohio. 16 Accept No Substitutes! Always Insist on the Advertised Brand!

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Water Tank Will Serve As Wind Tunnel For Airships IDED by the Navy Bureau of Aeronautics, Dr. Arnold M. Kuethe and his associates of the Guggenheim Airship Institute in Akron, Ohio, are building a water tank which will serve as a wind tunnel for airships. The tank, which will measure five feet by eight feet when completed, will be equipped with apparatus to simulate wind gusts by means of a water jet. A water tank and a submersible model of an airship must be used in the tests, because the model and the medium in which it is moving must have nearly the same density. A tiny “lighter-than-air” model would be too difficult to construct and handie. Since mechanical difi- culties render the lighter-than-air model im- practical, a water tank and a submersible model can be used equally well. Studies of what happens to an airship when a gust of wind hits it will be carried out and the experiments will serve to throw new light on why many big airships of the past have been defenseless against storms. The Society of Rheology, which is interested in the experiments, is a group of physicists and engineers interested in studying the flow of materials such as gases and liquids. Designer Of Mercury Vapor Engine Stresses Its Value William L. R. Emmet, designer of the Emmet mercury vapor engine, which uses mercury vapor much as an ordinary steam engine uses steam, claims that his type of engine, if applied to vessels like the “Normandie” would result in fuel and space savings of several hundred thousand dol- lars a year. The mercury engine, which has been used to run a power plant at Hartford, Conn., is theoreti- cally more efficient than steam because of the fact that mercury boils at a much higher tempera- ture than water. The efficiency of a steam engine depends on how hot the steam is. Chief hindrance thus far to its acceptance by engineers has been the fact that installation of the mercury engine is extremely expensive because of the high price of mercury. Once installed, however, the mer- cury does not need to be replaced and it produces more power per pound of fuel than steam does. NOTICE Changes in the make-up and title of this magazine, designed to make your favorite publication better than ever before, will be- come effective with our next issue. Be sure and reserve your copy now. Our new name will be—“MECHANIX ILLUSTRATED,” You'll be amazed at the speed with which you can learn in your spare time by Engineer Dobe’s Proven - Practical “Work - Job” Method. HERES A | . If you want to learn drafting as a profession—or if you want to ©, learn drafting to advance in your present work—Engi- neer Dobe can train you at home in your spare time by his long established, proren-practical Work- Job” Method. Send coupon TODAY for free book entitled “Success in Draftsman- ship.” o DRAFTING AT HOME From Engineer Dobe Engineer Dobe can prepare you just as he has trained thousands of successful students, aged 16 to 18 to past 50. His practical "“Work-Job” method requires no previcus experience. High school education not needed. He offers you a real opportunity’ to get a complete training in drafting right in your home in a surprisingly few months. Engineer Dobe teaches his students until thoroughly trained and until holding a good paying job. DRAFTING means OPPORTUNITY Modern industry begins with the draftsman, The drafting room is the nerve center of manufacturing, building and transportation. New inventions, new designs, new plens, basic improvements must begin with the draftsman. The draftsman has rich opportunities for advancement and better pay in scores of fields. In Machinery, Building, Aviation, Electricity, Transportation, Automotives—drafts- men must be used. Many trained draftsmen will be needed on better jobs at better pay and shorter hours, Send For FREE BOOK Mail the coupon today for FREE ilustrated book “Successful Drafts- manship”’ and full details of Engi- neer Dobe’s remarkable offer vthat includes all necessary tools A and equipment, Learn just a Trun : how you can be trained suc- — > a cessfully at home in your C Ig LSS spare time. Time is money. Ù Now is the time to prepare. Don’t wait another day. Send the coupon NOW for Engineer Dobe’s FREE Book, : {2S eee ENGINEER DOBE, Div. 4735, Libertyville, H. Send me your free book ‘‘Successful Draftsmanship.” lease explain how you assist your graduates to good I Positions as draftsmen. I I Name prem a a & S S a When Answering Advertisements Please Mention May Modern Mechanix 17

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Editor's Note: not require special research or involve trade secrets, scribed in thts issue can also be obtained free upon request. Your questions will be answered personally and free of charge by MM experts provided they do Names and addresses of manufacturers of new products de- reply. Address: Problems Editor, HOW TO ASK QUESTIONS Every day the Problems Department receives scores of letters in which are asked questions relating to articles which have appeared in MODERN MECHANIX, as well as questions on subjects of particular interest to individual readers. In both cases, MODERN MECHANIX editors are willing to be of as much assistance as possible—BUT the reader must not expect the impossible. Assistance can be given only when the reader asks a fair question. For example, a short time ago a letter was received in which the following question was asked: “I saw a man looking for a place to dig a well and he carried a short piece of wood in the shape of a ‘Y’. Under his arm he carried a can. Please tell me what was in the can.” The reader’s curiosity could have been satisfied im- mediately if he had asked the question of the man carrying the can. Another type of question, more common but quite as impossible to answer, is the one in which the question applies to an article in MODERN MECHANIX but does not identify the issue. For example, “I am building the radio set described in MODERN MECHANIX and instead of using the tuning condenser you recommend, I would like to use one of smaller size. Do you think this will be all right?” During the years MODERN MECHANIX has been pub- lished, many radio sets have been described. The editors have no means of knowing from the question which re- ceiver the writer is building. The editors therefore must write to the builder and ask him to identify the set either by name or the year and month of the issue in which it appeared. Time would have been saved by everyone concerned if the writer had taken the trouble to mention the exact issue carrying the article, When a reader is constructing something from plans pub- lished in MODERN MECHANIA, the editors are more than pleased to help when problems arise during construction. We are pleased to help for two reasons: First, we like to he of service to our readers, and second, we like to have MM projects completed satisfactorily. The question previously mentioned brings us to another important point applicable in varying degrees of importance io all how-to-build articles: ‘How can I change the design, size, speed, etc., of blank project?” To almost every question of this type, the answer must ‘be “You can’t.” It is true that if a table is described as being thirty inches high, the builder can make it twenty-nine or thirty-one and the table will be just as good. But un- fortunately, the average builder does not wish to make changes as simple as this. He usually selects projects not 18 Modern Mechanix, 1501 Broadway, Enclose a self-addressed and stamped envelope for New York City. lending themselves to changes without serious effects. For instance, every day’s mail brings many letters from good- intentioned boat builders who select a certain boat and ask our advice on increasing or decreasing the size of the hull, increasing the speed by using an engine of greater horse- power, changing the sail area, redesigning the cabin, or “improving” any one or more of a dozen points. To every question of this type the answer must be the same: “Follow the plans unless you feel competent to redesign the boat.” To many builders, this answer may seem harsh and dis- appointing. With those builders we sympathize because it is not difficult to understand that the future boat owner may wish to increase the speed of a boat by using an engine of higher horsepower. However, the answer re- mains “No.” Each boat was designed for certain general speeds, and the mere addition of power may not give the result desired. And as to giving answers to questions of the speed of a boat with another engine—that is impossible. Frankly, we don’t know. Any answer we would give would be the result of a guess, and our readers can guess just as easily as we can. Then too, many readers wish to change the dimensions of a boat. They select a boat of certain size and then ask us how to change it so that it will be eight feet longer. Such a procedure should not be attempted by anyone but a competent designer, because this is a problem of design more than one of construction. To supply the builder with a new set of drawings and construction details would cost far more than the reader would care to pay. Balance in a boat is a delicate and certainly an important quality. Therefore, do not expect to change an. inboard to outboard type, and vice versa, without being prepared to undertake the problem of re-establishing its balance as well as every other characteristic the boat may have. Even slight deviations from the plans in this matter may change what would have been a completely satisfactory craft into one suitable only for sinking at the first opportunity. A short time ago a reader wrote to us to tell us that he had built “Scram” but instead of the engine recommended —one of 40 to 50 horsepower—he was going to install one of 125 horsepower, and “how far from the stern should it be placed?” The editors knew that it should be placed much further from the stern than that builder suspected. In fact, it should have been placed out of sight, because “Seram” probably would shudder every time it came within fifty feet of a power plant of this size. Many readers would do well to read directions carefully before attempting to build a boat. If a man knows nothing about boats, understands no construction or nautical terms, he should spend some time learning the fundamentals before embarking on actual construction work. The editors have [Continued on page 21]

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AUDELS Practical Information in HandyForm,1540 Pages —1540 Illustrations. AUTO REPAIRS & SERVICE HELPS Allthe Parts of an Automob!le—Au- tomotive Physics—The Gas Engine — How a Gas Engine Works—Gas En- glue Principles — Multl-Cylinder En- gines—Horse Power—Automoblle Engines—Engines: Stationary Parts —Engines: Moving Parts —PIstons— Piston Rings—Connectlng Rods— Crank Shatts—The Valves—The Valve Gear—Cams and Cam Action— Valve Timing—Cooling Systems— Gasoline—Fuel Feed Systems—The Mixture—Carburetors—Automatic Choke—Super-Chargers —Transmis- sions—Synehro-Mesh—Clutches-—— Universals and Propeller Shafts—The Differential—Rear Axles—The Run- ning Gear—Brakes—Wheel Align- ment—Knee Action—Steerlng Gear —Tires —Lubricants and Lubrication —Automotive Electricity —Ignition Systems — Magneto Ignition—Spark Plugs—Iegnition Coils— Distributors —Automatle Spark Control—Igni- tion Timing —Generators — Starters — Generator and Starter Testing— Lighting Systems—Storage Batteries —Battery Charging— Battery Test- ing Troubles. AUTOMOTIVE DIESEL ENGINES Including Questions and Answers The contents Is progressively ar- ranged; thus making it & text book and a reference book, to which you will refer again and again. INSIDE VIEWS OF ALL AUTOMOBILE PARTS FULLY ILLUSTRATED. GOOD NEWS—JUST OUT AUDELS NEW AUTOMOBILE GUIDE is NEW from cover to cover. Explaining the Theory, Construction and Servicing of modern motor cars, trucks and buses; and the applcation of auto type Diesel Engines. Written by an englneerin and presented with forcefuldirectness in plain language and simple terms, generously illustrated. Itis an up-to- date authoritative book of instruc- tions giving a new vision of the auto- motive field. Covers the entire subject in every detail. Does not deallnidle theories, but gives definite directions telling exactly what to do and how to doit. Itis packed full with important °¢: information, indispensable to auto mechanics, service men and owners. TO GET THIS ASSISTANCE FOR YOURSELF SIMPLY FILL IN AND MAIL COUPON TODAY DOLLARS COMPLET 1540 PAGES 1540 ILLUSTRATIONS MO, FLEXIBLE BOUND-HANDY SIZE $ When Answering Advertisements Please Mention May Modern Mechanix authority Ẹ NEW 1938 AUTO GUIDE = N AWN Nunn TTT M mi Tipo tt a A, A Ml = Please eend me postpaid AUDELS NEW AUTOMOBILE GUIDE ($4) for free examination, If I decide to keep it, I will send you $1 within 7 days; then remit’$1 monthly antil purchase price of $4 is paid. Other- wise, I will return it to you promptly. EA PER Address... P P EEE TE EE 3 fo X Occupation........ E S A ames cea a eee TE am Ae 04 Referenden ss odes wee Res Roce ea ae ANE E RES MM

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Ttaly Surpasses America In Establishing Air Records Aviation records mean dollars in the value of airplane exports. It is more than coincidence that during the last two years, when the United States led the world in the number of aviation records held, aeronautical exports reached an all-time high, says Charles F, Horner, president of the National Aeronautic Association in Washington. The sad part comes because now Italy has re- placed America as leading world record holder. Last year the aviation record situation looked like this: United States .... records France records Italy records Germany records Great Britain .... record Russia. ennen EAN record Now, however, the aviation “batting averages” of the world have shown significant changes, and look like this: Italy .45 records United States . France ....... Russia ... Germany ... .14 records Great Britain ..0.....cccccceeseseeee 4 records Fully as dramatic as Italy’s climb from third to first in the record ratings is the rise of Russia from one record to 15 records within a single year, states Mr. Horner. A feature of the records race has been the battle between Italy and Great Britain for the world’s altitude mark. Since last summer first Italy and then Great Britain have alternated in pushing the mark higher, each time by approximately 2,000 feet. It is now held by Great Britain at 53,937 feet. Problems [Continued from page 18] been unable as yet to suggest any royal road to boat building. The editors cannot pass on the merits or marketability of an invention. These are problems the inventor should take up with his patent attorney. Many would-be inven- tors have an idea for a new device and write to us asking if this has been patented. This question is one for a patent attorney who will give an answer after a search has been made, if this is necessary. Some readers do not consider the fact that when thou- sands of letters are received a month, the time available for answering each letter naturally is limited to a reasonable amount. Some letters received contain twenty to thirty questions, each one of which would require 500- to 2,000- word answers. Those letters can be answered only by referring the writer to standard reference books available in most public libraries. MM editors have a sincere desire to help readers in their problems, but they can do so only with the help of the reader himself, —THE EDITORS. Do you like RADIO? Does the future of TELEVISION Interest You? Send for your FREE COPY of this book of FACTS Full of instructive Information’ on Employment Opportunities and Requirements You men who are sincerely ambitious to make good in radio and related industries will want a copy of this new book about employment opportunities and requirements, Written in plain, understandable language wilh no exazgeratlons and no mis-statements, this free book gives you facts you want to know about these profitable trades, 95 illustrations, Major subjects include Television Theory and Construc- lion, Pick-up Systems, Amplifiers, Transmitters, Receivers, Cathode Tubes, Sound-Recording on disc, Loud Speakers, Talking Picture Projection and Radio Communication, NATIONAL SCHOOLS is the oldest trade institution in the West. Established in 1905, Occupies its own modern three-story building, exclusively devoted to training ambitious men. Latest equipment. Selected, experienced staff of engineers and instructors, Many students can earn room and board while learning, National students are allowed coach railroad fare from any polnt in the United States. NATIONAL SCHOOLS Los Angeles " Request for FREE BOOK of Details NATIONAL SCHOOLS Dept. MMR-5 4000 So. Figueroa Street, Los Angeles, Calif.. When Answering Advertisements Please Mention May Modern Mechanix 21

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Na E ORN Shipped FREE on approval. Get a better job in the gigantic automobile industry. Make yourself an expert quickly with the help of these amazing automobile books, 19th edition, chock full of vital auto- mobile information. Put your finger on what you want to know without long§ search or study. The Jiffy Index (exclu- slve in these books) makes them an instant reference library. Take advantage of our great offer to ship them to you FREE for examination, Repair Any Auto Fault No matter how difficult a repair jee, may ecem to be you can find the enewer in these books which cover fully automehile operation, construction and repair. Best of all, they are right up to the minute with all the latest gadgets, appliances andismprovements covered, 2500 pag 2060 illustrations and wiring diagrams, together with articles on marine engines, a n motora, diesel engines. tractors, etc., making this the most complete automobile cyclopedia evar published. There are O creat big volumes in this brand new edition. Covera are flexible leatherette, gold stamped. In addition to these hooks, if you send now, we will include a membership for one year in the Ainerieun Technical Society, which entitles you to free consultation privileges with our automobile experts. Fit Yourself for Bigger Pay Bend the coupon now with your name and addrees only, (don’t send money). ee ee ee ee ee a m m a n a n AMERICAN TECHNICAL SOCIETY Drexel Ave. at 58th St. Dept. A5320, Chicago, Illinois T would like to see the new 6-volume edition of your AUTO BOORS. I will pay Lhe few conts delivery charges only, but if I choose, I may return them express collect. If after 10 davs use I prefer 19 keep them, I will eend you $2 and poy the balance ut the rate of only $) a month, until $24.80 is paid. Pleaso include free consulting membership as per your offer above, Attach le((er stating age, occupation and name and address of employer and that of at least one business man as reicrence. RADIO “REFRIGERATION” nUn rrn e TONER Leam Quickly-in Spare Time at Home ~ -by Practical Shop Methods OH New easy way to prepare for jobs leading to salaries od of $30,940, $50 a week. Opportunities to earn $5—$10 a =Œ Yreek and more while training, Learn by doing actual Jobs in your own home electrical shop. Electrical Bauip- PS dm} 0 ment and Apparatus supplied at no extra cost make training practical. No previous experience or advanced education necessary. Money back if not catished. Write for FREE BOOK of Facts and Opportunities for you as a trained Electrical Man, ELECTRIC INSTITUTE H. W. PETERSEN, President ° j Dept. 48E Hinsdale, Iiinois I NAMB AGE I | STREET. | i CITY. STATE. ! ee ee ee ee | “OIL DOES NOT WEAR QUT” (U. S. 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Does everything the expen. sive machines do! A big, sturdy, well constructe: d machine for lifetime serv- ice. Needed Ly retailers, professional men, etc. for sookkeeping, taxes, check- books. Visible totals. Quick —easy—accurate. AG ENTS— biggest money maker in yearst Take orders everywhere for first efficient. full size adding machine at LOW PRICE, Sells quick on simple demonstratlon. ADD-O-MATIC Co. 430 N. Oakley Bivd., Dept. B-10, Chicago, NI Write for free booklet describing ‘107 Plans for Operating a Successful Business of Your Own”. n Make from $20 to $100 a week starting in spare M time at home. No peddling or house-to-house selling. Booklet sent free, and without oodligation. Write for your copy today. ` ELITE PUBLISHING CO. REE 214 Grand St. New York, N. Y. BOOK Dept. G - STAR METAL BOATS We ex SINKABLE Pacha _ CARE-FREE. ‘ECONOMICAL A complete line of well-built metal rowboats, outboard motor boats, and sailboats. Save money—get betier quality at lower prices. STAR TANK & BOAT CO. Dept. M—Goshen, Ind, MAN IN EACH TOWN To Plate Auto Parts Reflectors, Bicycles, Fixtures, Mirrors, by tate method. Simple plan of manufacturing at home starts you IN GOOD PAYING BUSINESS, Write today for FREE particulars and proofs. GUNMETAL CO., Ave. P, Decatur, M. BOOKLET YOUTHFUL FREE Enjoy the vigor_that comes from relleving pressure en spinal nerves, 15 glorious minutes on Pandleulator gives pep like full gymnasium workout. Hundreds of hospitals, sanitariums and doctors use this great spinal corrective appliance. Send for FREE booklet, PANDICULATOR CO, 418 Newman Stern Bldg.,Cleveland,O. HOME WORKSHOP FANS Get full advantage from your shop by building that project you have long had in mind. No doubt you'll find it explained fully in the 1938 How-To-Build-lt book which contains plans for making midget racers, auto trailers, furniture, radios, games and toys. Sen your 50c now for this big 148-page book—contains 500 pictures and plans all in rotogravure. 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New De-IcerUsesEngine Heat To Warm Plane’s Wing Ice formation on airplane wings—that bug-a- boo of pilots—may be prevented by a simple and efficient system utilizing waste heat from the exhaust pipe of the airplane’s engines, it is re- vealed in a patent (No. 2,081,963) recently granted to two National Advisory Committee for Aero- nautics engineers. The inventors of the new “ice preventer” are Dr. Theodore Theodorsen of Hampton, and Wil- liam C. Clay of Buckroe Beach, Va. Readily installed in airplanes of any type— biplanes, low and high wing monoplanes—the system utilizes vapor heat by projecting it against the leading edges of the wings where ice generally forms. The heat warms the wings, and prevents ice formation. The vapor heat is produced in a boiler or tank which is built around the engine exhaust pipe. The waste, hot exhaust gases passing through the exhaust pipe, transfer their heat to the water in the boiler and vaporize it. The hot vapor travels through a pipe into a long, perforated, distribu- tor pipe which lies inside the wing adjacent to its front edge. Out of the perforations the heated vapor shoots in a series of jets against the leading edge of the wing. The hot-water vapor keeps the wings warm. The condensed vapor flows into pockets inside the wing, where it drains down pipes back into the boiler. It is again converted into hot-water vapor by the hot exhaust gases. Thus the ice- preventing system is a continuous one. To prevent the returning condensed water from freezing, a portion of the return pipe passes through the main pipe along which the hot vapors are passing to the wings. Another feature of the ice preventer is the inclusion of rain slots in the wings for collecting moisture flowing rearwardly from the heated parts of the wings. These collect and dump the moisture to prevent it from reaching the unheated rear surfaces of the wings where it would freeze. Installation of the ice preventer, say the inven- tors, does not disturb the balance or stability of the airplane. 6

New Use For Old ‘Squeegees’ QUEEGEE plates which have become too dull for further use, can be converted into serviceable developing trays for processing large prints. Bend up the sides and ends of the plates so that the tray attains a depth of about 11⁄2 inches. Do not cut the corners of the metal, but rather fold them over to form a flat-type waterproof joint. NOTICE Changes in the make-up and title of this maga- zine will become effective with our next issue. Reserve your copy now. Our new name will be— “MECHANIX ILLUSTRATED.”

For many years hair and scalp specialists hare known that inner stimulatlon of blood circulation in deep-lying scalp blood vessels stimu- lates growth of hair. Here is an amazing machine which, through

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TRIAL LESSON IN °C - DRAFTING More good Jobe now In Drafting. Learn AT HOME in aparetime (orat our Chicagy School), Send post card for FREE TRIAL LESSON and aea how easy to learn and get a good job. CHICAGO TECHNICAL COLLEGE E263 Tech. Bldg., 118 E. 26th St., Chicago, Iit, Iftyou"ean go away to college to learn Drafting, Engineering, Architecture. Electricity, Aur Conditioning or Radio—send Jor FREE Blue Book, Want a Career in photography? We give you personalized training. Commercial, News, Portrait, Advertising, Candid ov Motion Picture Photography. Big money- making opportunities, Or learn for pleasure. Personal Attendanca and Home Study courses. 28th year, Free booklet, NEW YORK INSTITUTE OF PHOTOGRAPHY 10 West 33 St, (Dept. 153) New York City HAWAIIAN GUITAR ex, The Hawalian way. Surprise and entertain your Dat friends. Amazing new simple method makes 7, learning to play from REGULAR PIANO MUSIC -< as fascinating as a game. Shows you in pice tures how to do lt. Previous musical training and talent unnecessary. Earn while learning by new plan. _ You pay for the lessons just as they are received. Write today for free information. A poste

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EARN BIG MONEY BLENDING CHEESE #7. CORN Make delicious new_food 3 ~/ sensation—Cheese Coated Pop- corn. Sell at wholesale to stores, taverns, restaurants, ele., We fur- nish complete outfit, including for- mula and instructions, Low priced. my Start at home, Particulars free, Send name and get all the facts free. CHEEZE-KIST COMPANY, 542 High Street, Springfield, Ohio, ROOFLESS PLATES Mouth Clear NO ROOF

wit tH 3 POINT SUCTION FEATURE ! Featherweight—no gagging—Natural Taste—Holds Better, Singers, Speakers like the extra tongue room, clearer mouth, All forms false teeth—by mail—as low as $9.75. 60-day trlal. Write for FREE catalog, impression material and sample. We trust you, Monthly payments, 462 HOD WILLIAMS BLDG., TAMPA, FLA.

HOD LABORATORY, 24 Accept No Substitutes! Always Insist on the Advertised Brand!

Page 25

Tiny Ball Bearings, Size Of Pin Head, Produced Tiny, precision ball bearings are now being manufactured in Switzerland. In overall size, including the ball race, they are no longer than | the head of a pin. They can be substituted for jewel and plain bearings in all forms of clock- work, motors, delicate machines and sensitive measuring apparatus. They are particularly useful for aviation instru- ments because they can withstand shock and vibration better than jewel bearings. Tests on the reduction of friction obtained have been made for comparison with jewel and plain bearing. The mean damping time for rotational motion in identical conditions was eight times longer than for plain bearings and 20 times longer than for tapered pivots. The ball bearings have an ex- tremely low coefficient of friction so that only approximately the same force is required for starting as for running. The smallest ball bearings now available (1.5 millimeter diameter) have three balls and the larger ones have eight. It is claimed they operate satisfactorily up to 10,000 revolutions a minute. Only 15 per cent as much oil is needed for lubri- cation as is required for plain bearings, so that they do not need lubrication for years in a small unit. The machined accuracy of the bearing is plus- or minus- 1/10,000 of an inch.

All-Welded Railroad Trains Predicted By Expert The railroad car of the future will be largely assembled by gas, arc, and spot welding, V. R. Willoughby of the American Car and Foundry Company, New York, declared before a conven- tion of the American Welding Society. Welded freight cars can carry 2.7 per cent greater pay load than the lightest riveted design, “a difference which becomes highly significant when the mileage of the average car is con- sidered,” Mr. Willoughby pointed out. Welded 70-ton hopper cars already built weigh 45,900 peunds compared with 50,200 pounds for the riveted ones. The welded cars are able, therefore, to carry 164,106 pounds of pay load whereas the load-carrying capacity of the riveted car is only 159,800 pounds. “Welded cars have behaved with entire satis- faction since 1930,” Mr. Willoughby said. “Skillful designers make use of other advantages of weld- ing. For example, the free discharge of cement from hopper cars practically requires the smooth interiors made possible by welding. Alloy steel and aluminum cars as well as tank cars for liqui- fied gases have also been welded with entire success.

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Nigh School at Home Go as rapidly as your time and abilities permit. W Equivalent to resident school work—prepares for entrance to college. Standard H.S. texts supplied. Diploma awarded. Credit for H. S. subjects already completed. Single subjects if desired. Bulletin on request. Specialized training is absolutely essential to Success today. Over 150 noted Educators, Engineers and Business Men helped prepare our spe- cial instruction material, used by many resident schools and colleges, S. Navy and Province of Mani- toba, Can. Train at home for best-paying lines as À listed below. No interference with present earn- ings while preparing for better job American School, Chicago Mail Coupon for Iinformation—-No Obligation American School, Dept, H-528, Drexel at 58th, Chica Tell me how to train for success in line checked p Chicaee High School Course in 2 Years Air Conditioning Electrical Refrigeration Architecture and Building Highway Engineering Automotive Engineering Liberal Arts (College) D Aviation Mechanical Engineering ness Management Private Secretary Ci Engineering Professional Accounting Complete Law incl. C. P. A. Coaching Diesel Engineering Radio and Television Drafting and Design Salesmanship Electrical Engineering D Steam Engineering A and up FOBFac’y 120 MILES PER GALLON POWER—1i4 or 2 IL P. Cushman engine. New 2-Speed Transmission—9-to-1 ratio in low! Climbs steepest hills, pulls Side-Kar with heavy load. Regular speed in high, ECONOMY--drug store has driven Auto-Glide 9,000 miles in 8 months for deliveries— 3-gal. of was a week—14c a mile! RUGGED —one owner traveled 1,000 miles a month for G mon tes no replacements! 3 models: (1) Auto-Glide, illustrated (2) Karl-Pac, with parcel carrier, (3) 3-wheel Side-Kar model— a carries extra passenger or 300 Ib. load. WRIT Send for free book, prices on new models. DEALERS: Write “quick for Speclal Ofer! CUSHMAN MOTOR WORKS, Dept, R-5, Lincoln, Nebr, BUILD YOUR OWN Electric Gutboard Motor from old auto generator. We show you how. Lightweight— Clean—Silent. Variable speed from standstill to maximum makes it ideal for trolling or casting. Operates 8 to 12 hours on 6 or 12 volt battery, Many olher important features. Dlme brings complete plans and valuable Coe ee LeJAY MFG. CO. 514 LeJay Bldg., Minneapolis, LOW FACTORY PRICES 20 Kayak designs also assem- bling kits with instructions for home building. Aquaplanes; Outboards, Rowing Shells, Ice Yachts, Sailboats, Snipes & National one design. SPECIAL GIFT OFFER,$6 DOUBLE PADDLE FREE. Whiletheylast. Writetoday. KAYAK BOAT CO. 152: EAST 129 ST. EW YORK. N. Y. Complete Cut-to-Fit ; ssembling Kits TEA AND CO PAYING UP TO Sc. 00 ANY A WEEK National company needs more men at once to make regular calls on local routes. No experience needed. Operate on our capital. 1 give producers brand-new Ford cars as bonus. Rush name on # postcard for DUE facts. BERT MILLS 5194 Monmouth, Cincinnati, Ohio, C TUBELESS BATTERYLESS WORLD'S SMALLEST REAL Amazing midget radio weighs only 3 ozs. complete, Receives stations wlth clear beautiful i ione. Should last for years ENTIRELY NEW DESIGN! Not to be confusedwith cheaply made imitations. Mechanical Patent No. 2074887 covers complete construction. Music and pr grams: COME DIRECTLY FROM FRONT QF RADIO. Has self-contained “«Speakophone’’ which gives superior performance. NOT A T TOY. The newest radio sensation of the year. lbsolutely complete with instruc- tions for use in homes, hotels, boats, etc. TAKES ONLY A SECOND TO CONNECT—no hookups to any current. SATISFIED OWNERS IN ALL PARTS OF THE€WORLD report wonderful service. THESE ARE FACTS. Beautiful two color cabinets in six color Pay postman only $2.09 plus postage on SEND NO MONE arrival or send S 99 (Check, M Cash) and yours will be sent postpaid. GUARANTEED. Can be ised by anyone. A most unusual value. ORDER a TINYTONE RADIO CORP DEPT. M-5 PERFORMING Kearney, Nebr, HAVE YOU SOME SPARE ROOM a basement or garage where you can do light work? We can offer you a profitable proposition, casting 3 & 10¢ novelties, ashtrays, toy autos, ete. as Manufacturer for firm of many years st No experlence necessary as we furnish full instruct: moulds. If interested in devoting spare or full time to prot work write AT ONCE stating age and space available as we are now closing arrangements for 1938 supply of our goods. METAL CAST PRODUCTS CO. {696 Boston Road, New York, N. Y. Dept, 2, Just couple your own en- gine to this unit, mount it on chassis and you have money making advantage of a portable welder at a saving of $300 to $500. HOBART BROS., BOX SM-58, TROY, OHIO i Gentlemen: Send me informatlon on ( ) Build Your Own Weld- er ( ) Electric Drive Welder ( ) 30 Days Trial, Easy Terms () Rental Plan, Also send me free books I’ve checked. NAMY veces cece nee c ene e erence eee ee anne nn ereeesenesen seas Address „uunossesapepnosssrenarsesereraseeresesset 30 DAYS TRIAL AT HOBART'S RISK _ AND EASY “PAYS FOR ITSELF” BOOKLETS ON WELDING,’ CHECK YOURS ANO MAIL THE COUPON TODAY. How to Build- YourOwn” L |Wew Profits in Are Welding | Wew Arc Welding Catalog New low prices make this profitable welding service available lo everyone. Opens doors to big pay jobs that carry real profit. Hobart Welders are easier to operate, faster, guaran- teed to bring you quality welding business . . . extra profits wlll pay for welder without expense to you. NO INVESTMENT TERMS—PROFITS PAY FOR IT Extra earnings and savings possible with Hobart Welders make lt easy to own without expense, You can even rent a new Hobart and later purchase it without loss, Coupon brings details. THE FASTEST SELLING ARC WELDER ON THE MARKET TODAY 26 Accept No Substitutes! Always Insist on the Advertised Brand!

Page 27

Probe New Matter Property What may be an entirely new property of matter has been discovered in one of the world’s rarest minerals known as “Hackmanite.” Found origi- nally in the rugged fiords of Greenland in the early years of the last century and later in the old crater of Italy’s volcano Vesuvius, Hackmanite has long been a treasured collector’s piece for scientific museums, for its rarity alone. Now a clear variation of the deep blue, lapis lazuli-like mineral may take on the added merit of research value. Samuel G. Gordon, associate curator of minerals in the Academy of Natural Sciences here, ex- plained the rare mineral and its new found prop- erty to Science Service. The American mineralogist O. Ivan Lee of Jersey City, N. J., has made the strange discovery that a quickly passing red-violet colored streaking of the surface of Hackmanite can be revived at will by radiating the mineral with ultra-violet rays, explained Mr. Gordon. For many years, continued Mr. Gordon, miner- alogists have known that when a clear variety of Hackmanite was fractured, characteristic and beautiful bright red-violet splashes of color ap- peared on the clean surface. Then, on exposure to ordinary light, they passed away. Radiation with ultra-violet light, Mr. Lee has found, brings back the lost property at will and as many times as one wanted to perform the experi- ment. The first thing which one might think of to explain this strange revival of a color-death would be fluorescence, at least in the ordinary sense of the term, he added. The flourescence of Hackmanite, that is its brief temporary glowing following exposure to light, is a characteristic salmon pink that cannot pos- sibly be confused with the bright red-violet shade of the revived colors. Neither is the happening one of phosphorescence since this property of Hackmanite yields a beau- tiful blue color. What really is the true explanation of the effect is thus unknown at present but at this stage of scientific research when supposedly the external properties of matter, at least, are well known, the discovery takes on added interest. Mr. Lee calls the phenomenon reversible photosensitivity. A list of addresses of manufacturers of items mentioned in MODERN MECHANIX will be sent to any reader upon receipt of a stamped, return envelope. NOTICE Changes in the make-up and title of this magazine will become effective with our next issue. Reserve your copy now. Our new name will be—“Mecuanrx ILLUSTRATED.” CAMERA + o e POPULAR PHOTOGRAPHY the most outstanding photographic magazine on the market today!... From cover to cover it's crammed with brilliant pictures, valuable information on all phases of photography, and interesting illustrated features and articles for every- one who owns a camera or likes pictures In the BIG Anniversary Issue {May} @ IVAN DMITRI... the world's outstanding user of Kodachrome gives you detailed information on how YOU can take thrilling naiural color pictures. Ilustrated with a 4-page color insert. @ DIRECTORY . . . a complete review of the world’s most popular cameras and accessories NEVER BEFORE PUBLISHED! @ LENSES and DIAPHRAGMS... the “Radio City Music Hall Corps de Ballet’ cooperated with Jack Price in producing a series of brilliant illustrations to demonstrate the subject of “depth of field’’ @ FILM CHART .. . a handy reference table of data on all commonly used films. ACT NOW.. SAVE ONE-THIRD! Take Advantage of our SPECIAL OFFER BIG ISSUES FOR POPULAR PHOTOGRAPHY 608 S. Dearborn Sireet * Chicago Enclosed find $1.00. Enter my subscription for the special introductory offer of 6 issues for $1.00. Start my subscription with the issue. Name Address City State OI prefer a one year subscription at $2.50 O Two years at $4 ($1.00 extra for foreign postage per year) When Answering Advertisements Please Mention May Modern Mechanix 27

Page 28

“When good fellows get together’—a fleet of four “Littl Bear” boats constructed from MM plans by Minnesota fans. PHOTOS of boats of all types and sizes from kyacks to sailboats as well as power boats fea- turing outboard, inboard and propeller-drive motors have flooded the Workbench this month, so in response to this expression of popular interest in home-built boats we are devoting the entire space to the subject. Norman Schauer, of St. Paul, Minn, was awarded first prize of $5, for his letter and photo describing a fleet of MM boats. The letter reads: Dear Editor: I am sending you a photo of four “Little Bear” boats constructed by George and Art Maguire, John Alden and myself, all of St. Paul. We thought you might be interested in the photo as the boats were built from plans in the MM book—‘‘How To Build 20 Boats,” 1936 issue. We are organizing a boat club and will soon have ten “Little Bears.” Hoping for more plans for small boats in the future, I am, Norman Schauer. Good work, fellows. The club angle sounds like a good idea and the 1938 MM boat book ought to interest your entire group. Copies are available from our Greenwich, Conn., office at the usual price of 50c per copy. 28 A photo and letter describing a very novel water craft won a $3 award for Fred Pilates, of St. Louis, Mo. He says: Dear Editor: As a physical culture specialist and a constant reader of MM I developed the "aircycle,” shown in the enclosed photo. It is constructed of bicycle paris, mounted on a surfboard which is balanced on pontoons. Total weight is 30 pounds, Fred Pilates, We have a strong hunch that reader Pilates will receive many inquiries from MM readers asking for construction details of his unusual craft. Mounting parts of a bicycle on a surfboard balanced by pon- toons, Fred Pilates constructed this novel “‘aircycle” boat, Modern Mechanix

Page 29

An interesting letter from far away Australia won a $3 award for H. V. Kenna. He writes: Dear Editor: I am a very keen reader of MM, especially the Editor’s Workbench, and feel that I am at last eligible to write to you as I have completed my version of “Whizzer,” the plans for which appeared in the MM boat book. The craft is powered by a motorcycle engine, fitted with a propeller of my own design and construction, and attains a speed of 20 m-p.h. H. V. Kenna. Inasmuch as reader Kenna is a licensed air- plane pilot, it was almost natural that “Whizzer” would tempt him as a construction project and he has certainly turned out a first class job. kok k Outboard fans will undoubtedly be interested in a letter and photo sent in by Warren Mathews, of Bound Brook, N. J., who also was awarded a $3 prize. He says: m Driven by an airplane propeller fitted to a motorcycle engine mounted at rear, H. V. Kenna’s “Whizzer” travels 20 m.p.h, Dear Editor: The enclosed photo shows “Buzzer,” built to MM plans. It travels about 22 m. p. h., powered by a 25 horsepower outboard engine. My next project will be an inboard job, built to your plans. Warren Mathews. Your “Buzzer” rivals many commercial boats in its appearance, Mathews, and we compliment you on your craftsmanship. ` Rk Another Minnesota reader who was awarded a $3 prize this month is James W. Spoor, of Cloquet, whose letter reads: Dear Editor; I am enclosing photos of a round bottom boat of my own design. It handles well with a 16 horsepower out- board and one of the photos shows its stability. I enjoy MM every month, especially the construction Projects. Let’s have more boat plans. James W. Spoor, May, 1938 Warren Mathew’s “Buzzer” outboard motorboat not only looks well, but sails well, too, judging from the above photos. Spoor’s boat certainly reflects his excellent knowledge of boat construction. However, with good plans and a few simple tools, reader, you, too, can build a small boat that will insure many healthy and happy: outdoor hours during the coming summer months, x k k A letter and photo describing a home-built MM kyack won a $3 award for Bob Nissley, of New Brunswick, N. J. His letter states: [Continued on page 31] James W. Spoor’s home-built 15-foot round bottom boat is so stable that a man can stand on the gunwale (top) without construction details. 29 shows r capsizing it. Lower photo

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| NEW INVENTION SILVER: NICKEL ) COPPER:GOLD,Etc We Amazing! New intention makes professional electroplating easy for everyone—at home. Just hook up LEKTRO-PLATER to dry cell batteries, auto battery, or home current—dip brush into metal solution—apply to any object just Uke palnt, Presto! See how old, worn, dull, tarn- ished surfaces are instantly covered with new, heavy, bright actual metal surface! You can electroplate Nickel, Silver, Gold, Copper, Cadmium, ete. Just “Brush” On The Actual Metal So easy, a child can do a fine job, Save money by renewing life of hundreds of useful and ornamental objects in home, office, factory. Make money doing electroplating for PLATE others in spare time at home. LI KE NEW! Materlals cost little—profits BIG. Silverware SEND NO MONEY ! Utensils Outfit costs only $1.00—ready to use. Gen- erous supply of Silver, Nickel, Copper Metal Jewelry Solutions, and cleaning compound included FREE of extra cost. Send no moncy. Rush Auto Parts name and address. Pay postman only $1.00 plus few cents postage on delivery of Lamps LEKTRO-PLATER, metal solutions, cleaning compound, and complete, simple directions. Fixtures Use 10 days. If not delighted, return outfit to us and we’ll refund purchase price. Rush Ornaments order NOW. LEKTRO-PLATER COMPANY, Dept: H-2153, 4208 Davis Lane, Cincinnati, 10. COMPLETE ELECTRIC PLANTS Onan A.C. plants furnish same current as city lines, 110 Volt, 60 Cy For farms, camps, con- struction Jobs. Operate radios, water systems, all appliances. New models, 350 to 5000 watt: 6, 12, 32 and 110 volt D.C. Models $5750 and up Also combination A.C -D.C units. Shipped complete, ready to run. Write for detalls. D. W. ONAN & SONS 1755 Royalston Ave Minneapolis Minnesota RA Di SHOP WORK $ structors who First Tell you--Then Show you how to doa this simple ‘‘Learn by Doing’’ method, Send the coupon today and I will tell you all BY ACTUAL & Prepare for RADIO, TELEVISION, SOUND EQUIPMENT OP- thing, .. Then You Do It Yourself, You don’t need pre- PAY AFTER YOU GRADUATE IN about my quick, easy way to train in 12 weeks. QUICK-EASY WAY TO TRAIN FOR ORTUNITIES. You learn on real eguipment ander expert in- vious experience or a lot of book learning to train by SMALL MONTHLY PAYMENTS Train first--then payin easy monthly payments starting 60 daya after your 12 weeks training, Earn While Learning. Employment, help after graduation. Electric Refrigeration Train- ing NOW included at no extra cost. BESS RB SSERP RBS HB BSS EST HSS Hado OK Coste Hlectrical School adio v. oyne Ele 00 S. Pauling St., Dopt-S8-1H, Chicago, IN. Dear Mr. Lewis: Please send me your Blg FREE Book, and detalis of your “PAY-APTER-GRADUATION’’ PLAN. NAME ADDRESS GITY STATE _____ Sa GS SSG DE SE ES SSSSSS REDE TBS Se 30 1001 Repairs In Home, Auto, Farm For Only New plastinoid “putty’’— , SO-LO— fills cracks, holes in tires, shoes, boots—any- thing of rubber, leather or cloth. Spreads on like butter. Dries tough. Waterproof, flex- ible, non-skid. Won't come off —guaranteed! 25c package (25 repairs) shows many uses. At any 10c or hard- ware store. EACH So-Lo LEARN W es AT HOME You can learn by our modern and original system of instruction every part of the Watch repairing Trade at home. You can earn money while learning and prepare yourself for a well paying position or start In business after completing our course of Instruction. Good watch repalrers are in demand and generally earn very good salaries. For pare ticulars apply to the WISCONSIN SCHOOL OF WATCH REPAIRING 524 E. Mason St., Dept. ©, Milwaukee, Wis. FREE LOCKSMITHS &55k If you are a locksmith, or cut keys, this Book wil! be invaluable. Write for it on your letterhead or business card. It’s FREE. H. HOFFMAN Co. 6846 N. WESTERN AVE., CHICAGO BUILD SIDE CAR! With or Without Motor Easy to Build—Loads of Funi! PASS. OR DELIVERY—FITS ANY BIGYCLE QUICKLY ON OR OFF—NOT A TOY Be First to own a PAL-CAR The Cost Is Small Wilh Comalele PLANS—Plelures—Insiruclions— 40c PAL-CAR, 408 N. Lawler, Chicago PAL-CAR PARKS AIRPORT EAST ST.LOUIS, ILL Offers you college education majoring in aviation Four courses lead to B. S. degrees in Professlonal Flight, Aviation Operations, Maintenance Engineering, Aeronautical Engineering. 100 acre airport. 14 buildings, 33 in faculty 9302 enrolled for Fall term, 6.400.000 miles flight training. 1,562 planes. 538 engines reprired aud rehullt in shops, Graduates with all leading aviation companles, Dormitories, dining hall on field. Sunimerterm July 5th. Catalog. Write STRAR, DEPT. MM-5 11th YEAR PARKS AIR COLLEGES EAST ST. LOUIS, ILL, CHEAPER T EN N | S Earn Money, Too! NOW —you can buy Wills’ fresh. genuine Eclipse SPLIT GUT tennis strings direct-from-factory for as little as $2.25 PER SET postpaid. Also—ex- cellent quality SILK at only 65c per 37 ft. coil, postpaid. Rush your order now! Satisfaction GUARANTEED. New 1938 CATALOG of Tennis Frames, Vises, equipment now ready. Get your FREE copy. Send today. H. E. WILLS CO., Dept. 2355, 1047 W. 47th St., CHICAGO, U, $. A. Accept No Substitutes! Always Insist on the Advertised Brand!

Page 31

Editor's Workbench Chips [Continued from page 29]

Bob Nissley, of New Brunswick, N. J., poses with the 12-foot kyack he constructed from plans in the MM book—'"tHow To Build 20 Boats.” Hull is painted green, but deck is natural. Dear Editor: I am enclosing a photo of a kyack which I built from plans in your “How To Build 20 Boats” book. Only a few minor changes were made in the final as- sembling, so it really is an MM boat. My kyack is 12 feet long, 22 inches wide, and 8 inches deep. The hull is painted green while the inside, keel and deck are varnished natural. Bob Nissley. Nissley’s kyack appears to be well constructed and we know he will have plenty of fun with it during the boating season. If you, too, are in- terested in building a boat get a copy of the MM boat book—“How To Build 20 Boats”’—and start construction now so you can launch your craft at the start of the summer. The book is priced at 50c per copy.

Every reader of MM is invited to send in photos and letters describing completed workshop pro- jects. We prefer to use photos of projects con- structed from MM plans, but we assure readers that consideration will be given to all photos. A list of addresses of manufacturers of items mentioned in MODERN MECHANIX will be sent to any reader upon receipt of a stamped, return envelope. When Answering Advertisements Please Mention May Modern Mechanix

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STOP THROWING AWAY PROFITS! DO YOUR OWN WELDING! Thats the modern way to Increase income and customer satisfaction. And, it takes only 22¢ a day to do it. Yes, you get the sensational, profes- sional, ALL-PURPOSE Common» Wealth Arc Welder—Model 120-FS, for only 22¢ a day. Ten whole y months to Py, out of profits, Now, y for the first time, it is EASY for every inventor, laboratory, home workshop owner, garage, repalr shop, and factory to afford a complete weld- ing service for manufacturing, repair main- N tenance, experimental or work. Works on 110 or 220-Volt A. €. Simply plug into a 110 or 220-volt, 60-cycle A.C. line. Economical—costs only a few pennies an hour to operate. Often pays for itself on first or second Job, Portable—can be carried right to outside jobs in auto, truck, or side car. Anyone can weld with its easy-striking, automatically- Stabilized are. Comes complete with belmet, electrode lulder, welding rod, cte. Nothing else to buy. Fully Guaranteed. Breath-taking low price! Saves’ and makes hundreds of dollars. Handies ALL Welding Sheet Metal to Heavy Castings Model 120-FS is a big, 110-pound, man sized, heavy-duty welder with efficlency of machines costing many dollars more. Welds iron, steel, cast iron. cast steel, and alloys of them. Six heats handle everything from fenders and light sheet metal to motor blocks and heavy castings. Also fine for soldering, and brazing. Uses stan- dard welding rods. No experience or special raining. needed to operate. Simple, complete instructions for doing all kinds welding jobs. in- cluded. MAIL COUPON BELOW for complete FREE details. COMMONWEALTH MFG. CORP. Dept. H-52, Cincinnati, Ohio

14 : ohio. bout Commonwea Cincinnath Sp all detalls about ur g2e-a-day at Davicch me at once, Bese Srccessories and your e der Wil = plan. Model 120-FS | Name

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Car Owners! Meet MASTER GLAZE = the sensationally different Iuster for new „and used cars! ot a wax - not an oil polish =not a paint ~ nothing that “smears” over the surface. ~ A creamy liquid — quick and casy to , py X apply! Gives a hard, glass-like surface. > Vly < Even gasoline cannot dull it! Lasts six AGENTS’? \\ months to a year! Amazing luster — beaue ‘Unusual oppos tiful, sparkling clean and brilliant! Doesn't tunity. Quick the demonstrator big profits. Good territory, Write today.

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Copies of SMECHANIN For handy reference with these handsome binders. | Made from beautiful red sim- :. ulated leather embossed in gold, the binders hold. six | issues each. Magazines are © conveniently bound with a snap and are held positively in place; holes need not be punched nor copies marred. MODERN MECHANIX and the year specified are stamped in gold on the back- :- bone. Volume I and Volume _ Ilto represent the first and last |. six issues of the year will also ' be imprinted in gold if de- - sired. Each $1.25 plus 15e postage in continental U. $. ($1.25 plus 75c postage elsewhere) eee Io MODERN MECHANIX | | Preserve Your _ Fawcett Bldg., Greenwich,” Conn, 4 Enclosed Ig §..-. for ..... MODERN MECHANIX binders. | =o Imprint year (years) ..... i i “Imprint year amf volume number (years and volume Í numbers} ooo. A { Rame ooo ee | Address ree | tiv | a oS ami tas in sia ii a eek maid ini ann sect mms ane @ Lighter, easier to 194 play, less bellows- ing, plus more beau- tiful tone and vol- g ume, — that’s how Soprani’s exclusive Ampliphonic fea- ture has simplified thia accordion. As- sures rapid prog- ress. Home trial. Easy terms. See your music dealer or send for beautiful free book. Write today. SOPRANI, INC. °°" Sihi LECTRICA “ENGINEERING: ONE YEAR condensed course prepares for technical work in the electrical field. Thorough training in principles, with practical applications in laboratory and shop. High placement record. Modern buildings, dormitory, dining hall, 46th year, Catalog on request. ELECTRICAL SCHOOL St i heme 235 Takoma Avenue eeter’’ Palmer. New York, with his Soprar.i Campus. Washington, D.C, E SUITS & BIG PROFITS _ Styles 3 In Made-to-Order Suits Show friends Made- to- ‘Order Clothes “Styled for the Stars” at hig sa New Fashions, Fabrics, in- spired by Hollywood i fa: isn tes. Buddy Rogers, Cesar . Tale orders sp: ime, arn Dig „pronta ° clothes gu: d to ñt mples Free. te today. Dept. D- Buddy FOSTE R, IN c., Rogers JIM 5 2253 So. Spaulding Av Chicago, Iitinois APPRENTICES PIG PAY GOOD FUTURE rou are interested in working yourself into a tid ly paid position in Aviation under o Arnen- tice-Flan—Write, immediately, enelesing stan MECHANIX UNIVERSAL AVIATION SERVICE CO. Dept. A Detroit, Mich. Hu MAKE oF PESCIMATING ONLY Radio-Electrical $399 IFAS TA LATAES sbookst RE 25 pieces genuine commercial apparatus wiih {g illustrated manual! Build radio circuits, 110- $ volt motor, extension shone, thief detector. arc light, are furnace, e eetri stove, generate ultra-violet rays, many m SAVE 60%—Send only sa. $9 for kit and 6 Radio-Electrical books (value over $10). Money back if not pleased. Order NOW! ELECTRICAL SALVAGE CO., yp Strathmoor Station Box 524-79, Lincoln, Nebr. BE SUCCESSFUL Read Invention & Finance—it’s your chance to make money. Two year subseription $7.00 entered upon promise 10 pay on receipt af first copy. Place your order by cutting out and mailing this advertisement. INVENTION & FINANCE MAGAZINE 80-H WALL ST., NEW YORK,N. Y. 32 Accept No Substitutes! Always Insist on the Advertised Brand!

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Diesel Motors Gain In China IESEL motor vehicles registered in China at the end of 1936 increased by 585 units, or 100 per cent, compared with the preceding year to total 1,110 units, according to a report to the Department of Commerce from As- sistant American Commercial Attache A. Bland Calder, Shanghai. Between 500 and 1,000 gasoline motor trucks and buses in China have been con- verted to use charcoal burning devices and despite the acknowledged loss in power on grades and the adverse effect of this fuel on such cylinders and pistons the use of such equipment is increasing, Mr. Calder reported. Diesel motor vehicles are favored in China because of the possibility of their operation on vegetable oils which are indigenous to the country, according to the report.

Fast Cooking Stove Is Cool COOL cook stove that boils cold water in 30 seconds and percolates coffee in 36 seconds has been placed on display in Chicago. This stove is a far cry from the old time cook stove that turned the kitchen into a hotbox and heated the cook’s temper. It was placed on display at the opening of the exposition of solid fuel in connection with the annual convention of the American Retail Coal Association. The stove burns anthracite or coke, and is the invention of Dr. Gustaf Dalen, a Nobel prize winner in physics. It embodies the principle of stored heat for cooking. Insulation keeps the heat concentrated. Its demonstrators said there is no radiation of heat and consequently all parts of the stove outside of the plates and ovens are cool. The temperature in the room, therefore, is not affected.

A list of addresses of manufacturers of items mentioned in MODERN MECHANIX will be sent to any reader upon receipt of a stamped, return envelope. NOTICE Changes in the make-up and title of this magazine, designed to make your favorite publication better than ever before, will be- come effective with our next issue. Be sure and reserve your copy now. Our new,name will be—“MECHANIX ILLUSTRATED.”

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Ship Selects Graveyard Ashore Nic Sprank Offers. $5.00 For Best Oddity Pe Bue REACHES GRAVEYARD! THE BARK UMVOTI, STRUCK: BY A HURRICANE IN THE INDIAN SEA, WAS DRIVEN ASHORE NEAR’ MADAGASCAR AND LEFT STRANDED IN A GRAVEYARD. A TOMBS TONE PIERCED HER HULL. Betty Burke, Malverne, NY. HEAR A PIN DROP! THE ROOF OF THE MORMON TABERNACLE,IN SALT LAKE CITY, REFLECTS SOUND SO DERFECTLY THAT A PIN DROPPED ANY PLACE IN THE AUDITORIUM rey ARE ME HEARD 200 FEET s Orizzatte, Port Aplhualer. ,000 T SHORE LINE OF THE UNITED STATES IF STRETCHED OUT WOULD MEASURE 103,000 MILES,OR MORE THAN FOUR TIMES THe D DI Gaerne TEAM ENGINE HAD WOODEN BOILER! — A’STEAM EN MeL ister, Pear River INTO SERVICE IN A PUMPING STATION AT THE FOOT OF CHESTNUT STREET, PHILADELPHIA,PA.,IN 1801 HAD A BOILER MADE OF WOOD.— = UKrag, Groza, Pa. Five dollars will be paid for the oddity selected by Nic Sprank as the best of the month. One dollar will be paid for all others ised on this page. Send end your oddity to Nic Sprank, Editorial Office, Modern Mechanix, 1501 Broadway, . Source or proof of each oddity must be given. ew York, Send all oddities separately, not with other manuscripts or letters.

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hes Zz hs $ $ A i $ £3 f ie f a MAY, VOL. XX NOI = W.H. FAWCETT PUB LISHER 1 ro - ass muy home as the press room, the world’s best editors and reporters on your staff, and the radio as your copy boy—this is not the dream of Jules Verne—but an actual accomplishment, avail- able today to anyone in the United States owning an ordinary. radio receiver. No thundering press will deafen you when your paper is‘printed, but instead, equipment contained in a small, attractive box, will. silently print your “latest edition" while you sleep, completing it in time for reading at breakfast. Facsimile transmitters and printers have hee an- nounced by two manufacturers, Finch Telecommuni- cations Laboratories, Inc:, of New York City, and RCA Victor, of Camden, N. J. Predicted to be in wide-spread use within the year, many large broadcast stations have ‘started tests with the system, and actual broadcasts on a definite schedule will be an accomplished fact as A PRIVATE newspaper with any spot in your soon as these tests are completed. Of great signifi- © cance is the fact that the Federal Communications Commission has granted the broadcasters permission -ło operate the facsimile equipment on the requiar broadcast frequencies. Translated into actual use, this means that when the householder is through - listening to his favorite station, he merely. turns a switch which will, at the correct time, again turn on the radio for reception-of the same station, but this time instead of sounds emitting from the loud- speaker, an up-to-the-minute newspaper will unfold. At present one of the largest eastern broadcast stations, WOR, is supplying this type of transmis- sion, though not yet on a regular schedule. {+ is being done both on the. regular broadcast channels as well as on the ultra-short waves. Plans are under way for regular service of facsimile transmissions _ early this spring. Among other stations that have received F.C.C. permission to make facsimile broadcasts are WGN,

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Chicago; KSD, St. Louis; WHO, Des Moines; WGH, Norfolk, Va.; WHK, Cleveland; KSTP, St. Paul; KMJ, Fresno, and KFPK, Sacra- mento. The facsimile recorder will be sold at a price no higher than the average good broad- cast receiver. When production is increased the price is expected to be reduced to that of the average medium priced midget receiver. With the exception of the recorder, no special equipment is required except the broadcast receiver itself. This new medium of entertainment and education is not to be confused with tele- vision, differing most widely from it in that its operation produces a tangible newspaper on which appears the printed word, photo- graphs, drawings, sketches and even adver- Inventor William G. H. Finch holding a newspaper printed by the recorder he developed. Below, right is shown the printing section of the Finch recorder. The arm swings back and forth across the paper in synchronism with the beam of light scanning the copy at the transmitter. While tele- vision remains -hiding around the mythical “corner,” fac- simile brings news, photo- graphs, sketches, and draw- ings into the home today. tisements. As the newspaper is produced, it can be removed from the machine and preserved if desired, differing from the con- ventional type only in size. Briefly, the operation of the transmitter and recorder is as follows: The copy to be transmitted—whether it is pictures, news flashes, line drawings or comic strips—in- volves no special printing or preparation because the material itself can be inserted directly into the transmitter. An electric bulb, throwing a spot of light, moves back and forth across the copy to be transmitted. This action is similar to that of the human ` eye'as it sweeps from left to right across a line of type. In its movement across the copy, the spot of light is reflected back into a light-sensitive photo~electric cell. When the scanning light strikes the white portions of the copy, it returns a full reflection to the light-sensitive cell. When it strikes a black area, no light is reflected, while for the shaded areas, a corresponding reflection is obtained. Because of the action of intermittent light at the cell, these reflections are changed into electrical energy or impulses. At the re- ceiver or recorder, these impulses operate a stylus sweeping in synchronism with the scanning light at the transmitter. Thus a

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“black” impulse will cause the stylus to make a black mark on the paper while a “white” impulse will not cause a mark. Radio facsimile service, as it is being considered by broadcasters, probably will supplement existing sound broadcast programs. It is planned that pictures and text will be broadcast on standard broadcast wave- lengths during the early ‘morning hours, between mid- wma Legs Army 990° Burnsides Army night and wn, so that Here are examples of pictures and maps produced by the RCA facsimile re- g da = x ai a corder. Although facsimile had been used experimentally by the army, it had complete bulletin will be never been adopted for regular use. In time of war, small portable receivers ready for the user when he and recorders could supply maps to widely separated groups at the same time. arises in the morning. A number of ultra-short wavelengths for day and night services also have been set aside. l The FCC requires that each. experimental station install a minimum of fifty receiver-printers for each facsimile scanner-transmitter. The experimental programs will determine, among other things, public reaction to facsimile broadcasting as a radio service, the best type of program material, and the technical requirements for both scanner and receiver. In use, the printer will be turned on automatically by a time clock in accordance with a pre-determined transmission schedule. In the same way, the printer is turned off in the morning when the facsimile trans- mission is completed. At this point, a really up-to- the-minute newspaper has been printed. Charles J. Young, RCA Victor engineer, with the facsimile receiver-printer he has developed for home use. Ordinary white or newsprint paper and carbon paper are utilized for reproduction.

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f° kta ie (Photo by Fairchild Aerial Survey) Aerial view of the Central Exhibit Area, Flushing Meadow, N. Y., showing the rapid progress being made Administration Communications Business Administration New York City Building Theme Centre—foundations and pav- ing for Perisphere & Trylon Mining and Metallurgy Consumers Medicine and Public Health Food=focal exhibit Fisheries Food Shelter—focal exhibit Textiles Stores—warehouse Utility—operations Test Building 17. 18. 19. 20. 21. 22. 23. 24. in the construction of exhibit buildings. Employment Office North Substation-—power Fire, Police, First-aid——Station 1 Field of Flags Fire, Police, First-aid—-Station 2 Empire State Bridge-—over Horace Harding Boulevard Beginnings, Distribution Building Overpasses-——Grand Central Parkway 24A. Extension, new level 25. 26. 27. 28. 29, Temporary station, Long Island Rail- road Corner of Transportation Zone North end of Amusement Zone Court of States site Portion of Government Zone (Please turn to next page)

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T gd r > e ao ye y + Leh -> fe as X $ B The buildings are not the only things that will attract atten- tion. The Fair’s special police force consists of men picked for their appearance as well as their ability, and their bright uniforms of military cut will catch many a feminine eye. 40 w York World's Fair Takes Shape aE a es dak LREADY ‘ahead of schedule. work on the grounds and buildings of the New York World’s Fair is progressing so rapidly that the opening of the exposition on April 30-of next year is well as- sured. A “face lifting” operation of: gigantic scope is being per- formed, and visitors who will enjoy the tree-shaded promenades, the close-clipped lawns, the placid lagoons and the smooth auto roads will never suspect that for many years this was the site of the city’s biggest garbage dump. Located in the Borough of Queens, on Long Island, part of the City of New York, the Fair is only forty minutes from the center of Manhattan by a five-cent subway ride, and is the focal point of prob- ably the greatest road, bridge and airport building program in the United States. The. fair now looks like a boom town, with workmen and supply trucks swarming all over the place. The winter of 1937-1938 was very - mild, with practically no snow, so there was no delay on any of the heavy projects. Of particular interest is a $2,000,000 electric power transmission system, capable of supplying cities as large as Cleveland and Baltimore. This large installation is necessary because many of the buildings will be windowless and will have artificial lighting and air-conditioning. The photograph at the top of this page shows one. of the eight 15,000 KVA transformers, weighing 56 tons apiece, which will provide the needed electricity. Modernistic to the last degree, the various ex- hibit halls will produce many a gasp from visitors. Bold treatment of shapes and colors will be evident everywhere, emphasizing the Fair’s theme—“Building the World of Tomorrow.” At the left is a view of the Textile Building in process of construction, a sample of the un- usual design that dominates the architectural planning. Modern Mechanix

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Test Chair Gauges Comfort EVELOPED to help furniture designers determine the best angle at which chair backs and seats should be constructed to provide maximum comfort, a mechanically adjustable posture-measuring chair has cali- brated indicators showing the angle of the back,.the height of the head-rest and the depth of the seat. By seating thousands of visitors at the winter furniture markets, and adjusting the chair until each claimed it com- fortable, furniture designers have been able to determine the specifications for a series of three comfortable chairs. pee: ee Pee Wrist Magnet Is Beauty Aid en aro developed for the use of beauty parlor operators, a small but pow- erful magnet, which is mounted on a leather wrist strap, provides a convenient means of holding hair pins in an easily accessible posi- tion while dressing a customer's hair. Avail- able commercially, the wrist magnet has also proved to be a valuable aid to carpenters, upholsterers, dressmakers and other workers who handle pins, nails, tacks or brads. The magnet is about one-half inch thick with a diameter equal to that of the average wrist watch, thus avoiding bulkiness. False Gems Easily Detected CCORDING to Samuel G. Gordon, asso- ciate curator of minerology at the Academy of Natural Sciences in Philadelphia, Pa., imitation gems can quickly be detected by means of a simple test that can be con- ducted in the home. The suspected gem is merely held against a chunk of dry ice and if the gem is genuine, a sharp crackling sound will be heard; otherwise—silence. May, 1938 Process Reinforces Oil Film NEWLY developed polymerization pro- cess is said to increase the film strength of mineral oil 40 to 60 per cent, making the oil practically spatter-proof. The process, which can be applied to all types of mineral oils effects a complete change in the oil mole- cules without changing the chemical content. The photo above shows untreated and treated oil, respectively. 41

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AR stalks-abroad in more A\ (A than..one unhappy.sjand today The threat.of war iSimmediate and sleep-disturb- ing in some other nationsmotnow actually: engaged? "Armaments, land, Sea, and air are bimg built Up with tmprecedented aécelera- tion, in every-cornerl oi the earth, One new note one recent* trend, is -distizietly “discernable im the present armSaracesnot, apparent in any of this@*whichwhave.gone beferewethat.,.is. the greater em- phasis on air forces, and, théir equipment. A distinguished- mim- tary authosity recently pointed outAhat England, Germanysand kaly atleast, of theworld: powers, were spending more,of their re- armament funds ontaviation mač terial than onveither their armies or their navies. At such atime it may not be PLANES and MEN > -amiss to take-stock ‘of otr Ownmair by ae afm, td “examine critically and Brigadier General carefully the state 6feffectiveness Re ag : = © »G@£-our own Air Force. “Is our 5 H. H. Arnold, bes military aviation, well-may the : 2 ; : patriotic taxpayer ask, “equipped, oe eae aby ee ee tained and qualified to guard our f | sky frontiers?” Let us make a Cl arifying a maze searching appraisal, looking to- ward a fair answer to this timely of claims” and and much debated query. counter- ‘claims, | In times past many writers and public speakers have deprecated Brigadier General the fow standing of the United Arnold evaluates States among the world air ; powers. There has been much mae ES the Air Corps. chiding and berating of our na- a ine ote gone R tional fathers because of our so- General H. H. Arnold, above. called decadent air defenses. It was quite a shock to such critics recently, therefore, when no less an authority than Jane’s in its annual work, “All the World’s Aircraft,” made the following statement about military aviation in this country: “The United States has one of the biggest and possibly the most efficiently armed air services in the world.” There represented are the two extremes to the question. As usual, somewhere in between lies the true answer. Here it is as I be newly developed twin-engined Curtiss ` Y1A-18 mid-wing “ph lane-laboye) geniene a startling change in attack plane Modern Mechanix

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Designed primarily for attack tactics against huge bombing planes, the Beil “Airacuda” E pusher-type fighting plane is į armed with six machine guns. + ee eee see it. First, for a statement of the measurements by which we compare air forces. Their effec~ tiveness depends upon a number of constituent ingredients. These are: Airplanes: number, type, charac- teristics, accessory equipment. Operating crews: number, type, and state of training—pilots, gunners, bombers, navi- gators, radio men. Maintenance crews: number, state of train- ing of maintenance men, for servicing, repair and overhaul of planes and engines. Air bases: flying fields, shops, hangars, bar- racks, safe harbors for machines and men. The state of the aircraft industry: how May, 1938 rapidly can reinforcements and re- placements be supplied? What are ~ the resources in raw material and personnel recruiting available? Probable missions: Geographical location, isolation, probable ad- versaries, probable allies — war plans. There you have the constituent variables—machines, men, bases, resources, missions — by these yardsticks shall we judge Air Forces, We have more than one thousand modern fighting planes in our Army Air Corps, divided into the type categories, pursuit or fighters, bombers, attack, and reconnoissance and observation. These planes, type for type, are the equal of those found elsewhere in every case, and in several types we are distinctly superior to those pos-' sessed in quantity by any of the other lead- -ing air powers. In this connection a word of warning is well sounded. Our present favorable posi- tion in airplane and engine development is 43

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Featuring a wingspan of 150 feet and powered by four 1,000- horsepower engines, the Boeing XB-15, or “flying fortress” as it is popularly known, is believed to be the largest and fastest bombing plane in the world. The development of these huge planes necessitated a complete revision of military air tactics. Piloting is only one. phase of the intensive training of a modern military flyer. Shown above is a cadet class at Randolph Field, ‘Texas, practicing radio transmitting and receiving, or. buzzer” as it is termed by the student pilots, the messages being sent in: dot-dash code. -Airplanes can’t fly unless trained ground crews keep them in. first clase condition, so Uncle Sam trains mechanics, too (above). 44 - due primarily to the funds and effort we have expended during the past twenty years in funda- mental research and experi- mental engineering. During the years since the war, we in this country, the army, navy, National Advisory Committee for Aeronautics, Bureau of Air Commerce, and aeronautical in- dustry combined to spend more money on fundamental research and aeronautical experimenta- ‘tion than any of the other na- tions. During the past year there has been ample evidence that several of the other powers realize fully the reason for our favorable position, for some of them are now expending vast sums on wind tunnels, experi- mental laboratories and engi- neering establishments. In three to five years, therefore, we may well expect, in fact it is a fore- gone conclusion, that these na- tions will surpass us in airplane excellence and performance. The only alternative is for us in this country to bestir ourselves and increase by at least one-half, and preferably double, our funds, resources and effort in aeronautical experimentation and research. Today, however, our position is an enviable one. Our newer planes surpass, for the purpose for which designed, the proto- types found elsewhere. There is not a four-engined, long range, high performance, high capacity bomber abroad which its owners would not gladly exchange for our “Flying Fortress,” the Boe- ing bomber. There is not a Modern Mechanix

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fighter in any land which has created the stir and been ac- corded the adulation and praise heaped on our Bell “Airacuda,” multi-seater fighter, the world over. Our attack planes, of which the Northrop is the single engined version and the Curtiss A-18 the twin engine prototype, are preeminent in their fields. Our single seater fighters, Se- versky P-35 and Curtiss P-36, are excellent pursuit planes. Some fighters may be found abroad slightly faster, but few, if any, possess all the many characteristics, many of them antagonistic the one with the other, as are combined into these sleek, little, metal air destroyers. On the score of total numbers of military aircraft, five or six of the nations of the world ex- ceed the United States, but we take no small comfort that on the score of quality and unit effec- tiveness, there is little question but that we go to the head of the class. Air bases comprise an abso- lutely essential element in any effective air force. The finest planes in the world will be mired in the mud, inert and useless when needed, if proper basés are not available from which they can be cast into the air, groomed, manned, tuned up and armed for effective fighting might. Millions of dollars have been spent by the Army during the past few years in an effort to provide up-to-date air bases. There has been much improve- ment in living conditions for officers and men; shops, hangars, May, 1938 The “ground school” training of future Air Corps pilots involves attendance at lectures devoted to photography, navigation, aero- dynamics and a score of allied subjects. Shown above is a class attending a lecture on the operation of various aerial bomb sights- A class in soldering and brazing technique at the Air Corps Tech- nical School. Chanute Field, Ill, is shown in photograph above. 45

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Many modern commercial airplanes are so designed that they can easily and quickly be converted into bombing planes in event of war. The cross-section sketches above show conversion of Lockheed transport. runways and gasoline and oil storage have been provided at many regular army flying fields. Notable illustrations of recent effort now in progress may be seen in the new Northwest Air Base, McChord Field, Tacoma, Washington, and Hickam Field, Hawaii. Air bases are expensive installations. Funds which have been available have not permitted simultaneous completion of all our needed bases, but work has progressed as rapidly as budgét limitation would permit. There is every evidence that our present plans will progress to steady fruition, to the end that we shall have within five years ade- quate air bases well located and suitably equipped for the defense of the nation. Now for a consideration of our standing concerning men, operating and maintenance crews, their training discipline, numerical strength and general effectiveness. Regrettably, we are weakest on the per- sonnel side so far as numbers of pilots and combat crewmen are concerned. We. are short several hundred trained airplane pilots properly to man the planes now nearing com- pletion. Our War Department is mindful of this deficit and legislation is now pending in an effort to overcome this deficiency. Not alone have we been handicapped by lack of trained pilots in sufficient quantity, but there is a dearth also of bombers, gunners, naviga- tors and radio men. A new branch of our technical school has but recently been opened at Lowry Field, Denver, Colorado, in an effort to supply these men in greater quantity. This is a serious problem, but it is half solved when we realize it and form plans to correct it. Fortunately, those men we have, thanks to the General Headquarters Air Force, are well trained; they are organized into tactical units on a sound functional basis, the tables for which have been worked out and perfected during the past year. There is not the slight- est doubt in my mind that our Army Air Corps personnel, pilot, machine gunner, bomber, radio man, photographer, and navi- gator, man for man, is the equal if not the superior of those found anywhere in the world. Their training has not been theoreti- cal alone; it has been tested by thousands of hours of flying, millions of rounds of live [Continued on page 118] Ready for a training flight. Pilots of a squadron of North American BT-9 basic training planes warm up \ their sleek “sky chariots”, Note radio antennas.

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es i aa iati Mirror Teaches Batting A huge mirror mounted on a wooden frame constitutes a new method whereby baseball “rookies” are taught proper batting form at the St, Louis Cardinals’ winter training quarters at Oriando, Florida. Standing before the mirror, the player swings his bat and quickly improves his reflected form. Sun Operates Gas Machine Developed by Otto H. Mohr, of Concord, Calif., a specially constructed machine utilizes the sun’s rays to produce a gas which, when broken up by means of an electric current, yields hydrogen and oxygen. The hydrogen and oxygen are then stored in separate tanks for cooking, heating, etc. ee Hospital Boasts Safety Chute The Piedmont Hospital in Atlanta, Ga., is equipped with a spiral chute by means of which bed-ridden patients can reach the ground quickly in the event of fire. On each floor of the hospital there is an entrance to the chute and in an emergency the patients are slid down it on a mattress. 47

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Shown above is a section of the interior of the Parke Miniature Circus. Rings and stages are only 14 inches in diameter or square. Clyde W. Parke, of Memphis, Tenn. (right), whose skill as a whittler enabled him to create his famous miniature circus. OR years, Clyde W. Parke, of Memphis, Tennessee, had been hearing the jibes and laughter of his friends as they watched him toil away with penknife and scraps of lumber. For years he had given them the same friendly smile and the same good-natured answer: “You'll see. One of these days I’ll have the greatest circus in the world!” It wasn’t a facetious remark; it was a prophesy. For today Mr. Parke is the owner of the world’s most intriguing miniature circus. He is a modern Jonathan Swift, but on-a more magnificent scale. Both creators of Lilliput, Mr. Parke differs from his ancient contemporary in that the creatures of his vivid imagination manifest themselves in 48 Pigmy figures carved in wood, instead of fictionized characters. For thirteen years, beginning at the age of 37, this versatile “Master Whittler” has ‘whittled, scraped and gouged at bits of wood. He has accomplished a gigantic feat. His “show” is not a mere collection of carved wooden “people.” The Parke Miniature Circus is a vast congress of more than 300 animated lifelike actors and animals, each of which does something different. Every thrill- ing stunt you have seen pulled off by daring performers in the big shows is faithfully du- plicated by Parke’s mechanical midgets, which are whittled to the scale of one inch Modern Mechanix

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“Robert M. Hyatt A view of the side show entrance to the miniature circus is shown above. Note the ticket wagon and ballyhoo posters. Right—A comic police patrol wagon exhibit. to the foot. The Big Top is replete with thrills galore. There are—but wait. The best way to see a circus is to go. So step up, folks, and join the long line of eager fans buying tickets at the bright little wagon. We have taken (in imagination) a turn about the “grounds,” which are all of twenty feet long. We have had our curiosity ac- celerated by the antics of Firenza the Fire Eater, Stiletto the Knife Thrower, and JoJo May, 1938 Circle, above—-One of the tiny show’s floats— a Far Eastern Empress carried by slaves. Above —The menagerie tent with its animal wagons. The “Big Top” is shown in background of photo. the Dog-faced Boy. We have heard (in imagination) the husky bellowing of the barkers and spielers in front of the Side Show Tent, which is a three center-pole affair, six feet long, aflutter with gay banners adver- tising the wonderous sights to be seen inside. We have watched, goggle-eyed, the Sword 40

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Boasting a height of 18 inches, the giraffe realistically looks over the top of his cage. Swallower gulp a wicked looking blade; the Magician produce a squirming rabbit from nowhere; the Fan Dancer in seductive wiggles; and the Snake Charmer slithering amongst her venomous charges. With bursting curiosity we line up to get ‘inside. With the big show coming off in a few minutes, we cannot spend much time in the Side Show. After taking in the lesser spectacles here displayed, we move toward the Big Top. First, however, we must stroll through the Menagerie Tent. This is eleven by three feet in size. Around the sides are the animal cages. The center is roped off for the elephants, zebras, camels, and other large grass eaters. There is a plentiful sprinkling of straw on the floor, and here and there a tiny bale of hay. At one side of the arena a long, spotted neck topped by an un- gainly head, rises above the high fence. It is the Giraffe and apparently all is well up aloft! The Main Show Tent merits some descrip- tion. On each side is the Reserve Seat section —eight sections of 80 seats each, with foot boards and backs. The spectators seated here are cooled by 16 midget electric fans. At last seated (figuratively), we glance around the sparkling interior. Countless tiny ropes hold up, with the aid of block and tackle, the pole assembly of the entire tent. Our eyes are dazzled by the clusters of lights around each pole. There is the trapeze rigging, the aerial wheels, and all the parapher- nalia used by the Bight life-like horses draw the gayly colored Band Wagon, with its rhythm- swaying musicians, as it enters the arena at the head of Grand Parade (right). 50 - (right) is a big favorite little actors. But we are not given long to indulge in these commonplace essentials. With a mighty flourish the Grand Parade enters the arena at one end of the Reserve Seat section, and all eyes focus upon this colorful display. First into view comes six prancing whité - horses, drawing the band wagon resplendent in red, white, black and gold colors. The spirited, high-stepping chargers give us as much thrill as does the driver on the seat, swinging his reins and swaying his body to the mythical rhythm of the five-man orches- tra behind him. Immediately following this appears several floats. There is “Little Red Riding Hood,” “Peter Pumpkin Eater” and the “Old Woman in the Shoe” with all her brood. Then the most dazzling of all the floats—Queen of Sheba, seated on her gaudy throne, sur- rounded by realistic fire urns, and haughtily gazing out over the backs of her six white horses. On either side and behind her stand servants dressed in white, each waving a palm fan over Her Majesty. Still another float is that of some Far Eastern empress. She is seated on an ornate pal- AEN LIE X The Monkey Wagon with spectators at the midget circus, The monkeys, skilifully carved, are shown in typical simian antics. A llama and monkeys riding horseback are featured in this group of midget circus animals, All are carved from wood.

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angquin borne on the backs of six stalwart Nubian slaves. At her feet crouches a snarl- ing tigress. There follows the yellow and white wagon bearing a huge hippopotamus. He seems quite content even in his cramped quarters, since the bed of the wagon is composed of a tank of water (a glass top creating this illusion) where Mr. Hippo may take a dip. '. The Monkey Wagon causes a howl of ap- plause. Here several of the amusing little simians disport themselves in all the tricks Majestically, two lons (above) survey spectators known to Monkeydom. from their cage. Note the oil can atop one wagon. The next wagon might have arrived from Greenland. Giant icicles hang down over an icy blue background, while the roof is a replica of the flashing Aurora Borealis. Within, reclining in his proper environment of gleaming snow and icebergs, is a giant polar bear. There is a wagon of serpents and so realistic are they that many. in the audience refuse to touch even the wagon! Following this are the gorgeously bedecked wagons with lions, leopards, kangaroos, gnus, a tank of seals, black bears, and many other animals. There is a ponderous rhinoceros, one of the rarest beasts in captivity, and several gangling giraffes. Mr. Parke here calls our attention to something that may surprise many of us: The giraffe’s tremendously long front legs are in reality no longer than his seemingly shorter hind ones. It is only because his shoulders are so high, causing his back to slant at a grotesque angle, that his front legs appear longer. [Continued on page 118] Above—Three of the unusually detailed me- nagerie circus wagons. . Serpent Wagon ex- shibit, shown above. x Even a Lilliputian circus must have a feeding time for its animals, as shown in the photo above where elephants, zebras and a camel tackle some strewn hay. Right— A polar bear nervously paces his wagon cage as part of the “biggest little show” routine performance.

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Model Plane To Serve As Target For Artillerymen Paul. Whittier, veteran pilot, examines the ground radio equipment which will be used to control this 12-foot gaso- line-powered model when it is used as a flying target during coast artillery maneuvers to be held in California. Tiny Tea Set Worth $2,000 MINIATURE Queen Anne silver tea set, valued at $2,000, was recently placed on exhibition in New York, N. Y. The novel set comprises a tiny. tea pot, coffee pot, sugar bowl, cream jug, six cups and saucers and six teaspoons, all bearing the maker’s hallmark © of Jonathan Clifton, which was registered at the Goldsmith’s Hall in London, England, during 1703. The miniature tea set has an interesting history, having been found in the safe deposit box of an English lawyer after his death. Re- search indicated that the set had been given to him as a child by Lord Cornwallis, of Suffolk, England: Apparently, according to experts, the tiny set was originally planned as fur- nishings for some child’s doll house. A cigarette serves well as a size comparison for this tiny Queen Anne silver tea set which is said to be worth $2,000. 52 OWERED by a three horse- power gasoline engine and equipped with controls that can be operated from the ground by radio, a huge model airplane will soon be used as a flying target by a unit of the 63rd Coast Artillery during maneuvers at Muroc Lake, Calif. If successful, trial flights of the miniature airplane will pave the way for general use of gas- powered models to train anti- aircraft and coast artillerymen. The model plane has a wingspan of 12 feet and its 844-foot fuselage houses a special three tube radio receiver, which actuates the elec- tric motors operating the controls. Machine Tests Peas’ Quality so This young lady is placing peas in a new canning machine which performs the odd job of measuring their tenderness. UMBERSOME in size and featuring parts made from heavy iron, a new canning factory machine is designed for the delicate job of measuring the tenderness of peas. The peas under test are placed in a hopper on the machine and the force required to shear through them is recorded on a scale. ` Modern Mechanix

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Simplified Deep-Well Pump Increases Efficiency 50% Assembled Quickly, Weighs 30 Pounds 50% increase in efficiency over conven- tional deep-well water pumps using equal horse-power is claimed for a new.light- weight pump cylinder recently developed by H. H. Raulerson, of Long Beach, Calif. The outstanding feature of the new cylinder is that it achieves the action of two pumps in one through use of a single plunger, which de- livers a constant flow of water on both up and down strokes while reducing the water resistance. Instead of “breathing water” to eliminate vacuum resistance in the lower chamber, the new cylinder lifts to the surface all of the water which it takes in. Simplified in construction because of the single plunger theory its operation is based on, the new pump weighs only 30 pounds compared to the 90-pound weight of conven- tional pumps of equal size. The cylinder head is a multiple-purpose type, serving as a sucker rod guide, valve guide and packing box. The entire cylinder can be quickly as- sembled and is so constructed that any part can be easily replaced if necessary. May, 1938 Night View Of Edison Tower Makes Striking Photograph Memorial Marks Site . Of Early Laboratory HE striking photograph shown above is a night view of the $100,000 Edison Memo- rial Tower at Menlo Park, N. J. The tower, which is 131 feet high and is surmounted by a 14-foot replica of the famous inventor’s first incandescent lamp, marks the site of the laboratory where he produced the first practical electric light. The memorial was officially dedicated on February 11, the ninety-first anniversary of Edison’s birth. The replica of the incandescent bulb, which is atop the tower, consists of 164 pieces of glass cast in two-inch diamond patterns around a steel skeleton frame. The interior of the giant bulb features 960 incandescent lights and a 24-inch reflector. Because of its brightness, the tower bulb serves effectively as an airways beacon. Inside the tower base is an Eternal Light, which was set aglow by Edison on October 21, 1929, during a celebra- tion the inventor was attending at Dearborn, Mich. Thousands of tourists are expected to visit the memorial during the height of the coming summer season.

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Working scale- models intrigued many visitors at the New York Society of Model Engineers Exhibition recently held in New York, N. Y. Left—A gas- oline-driven power boat that can go 35 miles per hour. The ever increasing interest in, model railroading was evi- dent at the show where detailed loco- motives and freight cars, like those be- low, were rated as star attractions. An operating roundhouse (above) was a feature of the model exhibition. Modern Mechanix

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Next Month—We Change Our Title! Look for the New MECHANIX ILLUSTRATED EGINNING with the June issue (on sale May 10) this magazine will be called MECHANIX ILLUSTRATED. It will have more pages and more pictures than before. The cover, reproduced on the right, will be a striking color-photograph, with the new name displayed prominently across the top. Look for MECHANIX ILLUSTRATED on the newsstands on May 10, and buy your copy early, before your dealer’s supply is gone. You will find that the new MECHANIX ILLUSTRATED has more pages, more pic- tures of new inventions, more feature articles, more workshop plans, more “kinks”—and by far the largest and best photography depart- ment of any magazine in the field. The price remains 15 cents—and the June issue of MECHANIX ILLUSTRATED will be the biggest 15 cents worth of magazine you ever enjoyed. Tiny Stage Coach Model Valued At $1,500 Valued at $1,500, a tiny model of an old-fashioned stagecoach was recently placed on exhibition at an industrial design show held in Pasadena, Calif., to show design progress during the past three hundred years. The model is perfect in every respect and features leather upholstery, glass lanterns, straps and harness parts. May, 1938 Apparatus Breaks Germs With Tonal Waves A new apparatus, which by producing supersonic tonal waves, breaks up typhoid fever bacteria and other germs, has been developed by Dr. Leslie Chambers, a Philadelphia, Pa., research — worker. The supersonic waves produce a single note, about two octaves above piano range, re- sembling the shrill note of a peanut roaster. an on

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Right—Placing seeds on scarecrow to attract birds. As birds grew bolder, they alighted on farmer (left). SEOOLING © he BIRDS IRD lovers who would like to make friends of members of feathered flocks frequenting nearby woodlands will do well to follow a system devised by a German farmer. He placed some bird seed on the brim of a scarecrow’s hat and in the bowl of a pipe placed in the dummy figure’s mouth. This process was repeated daily. Then, one day, the farmer donned : the scarecrow’s hat, reclined on the ground and—the A “tamed” starling alights on scarecrow. birds came to feed off the hat as usual. Ice-Making Unit Mounted On Trailer-Type Truck OUNTED on a trailer truck so that it can be easily moved from place to place, a newly developed ice-making machine is capable of producing nearly five and one-half tons of ice every 24 hours. The entire assembly com- prises a brine cooling system, an ammonia compressor, a con- denser, economizer, water pump and an oil engine. The unit was designed for use in communities _where fruits and vegetables are grown, but where refrigeration Easily transported from place to place, this complete ice-making unit is Jig: a capable of making nearly five and one-half tons of ice every 24 hours. facilities are lacking. 56 Modern Mechanix

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New Tool Exerts Pressures NEW tool for scientific research which develops pressures of 1,500,000 pounds per square inch, a maximum exceed- ing any pressure previously at- tained, has been developed at the research foundation of the Armour Institute of Technology. Many new fields of research are now open with this device, in- cluding the earth’s structure 200 miles below the surface, and be- havior of untapped energy in the interior of the atom. The photograph shows Robert - Williams (left) assistant, and Dr. Thomas Poulter, director of the research foundation, demonstrat- ing how the equipment develops a 1,500,000-pound pressure per square inch. Note the massive size of the bolts and nuts holding the top section. Lock Raises Vessel 60 Feet Ni - IA Ba The stern wheeler, "The Dalles,” is dwarfed in the gigantic lock at Bonneville Dam, which can raise vessels sixty feet. Ocean craft now can travel 200 miles up the Columbia River. HIS large lock can raise vessels going up the Columbia River, sixty feet, a world’s record for a single lock. With the completion of Bonneville Dam and locks, Dalles, Ore., 200 miles from the sea, hitherto an inland point, now becomes a seaport. May, 1938 Up To 1,500,000 Pounds With this tool, pressures up to 1,500,000 pounds per square inch are possible. This new device opens new fields of research including the behavior of untapped energy in the atom and the earth’s structure 200 miles down. Device Shows Bus Location ONDON Transport plans to try an ex- periment never before attempted any- where in the world, and if successful for regular use, will give the main office of a bus transportation company a “picture” of the city’s moving buses. Each bus will carry on its roof a coil of wire through which will pass an alternating current. At certain fixed points a wire will be suspended across the road where the bus will pass. As it passes, it induces a current in the wire which in turn records the passing on the “clock.” This “clock” will record the movement of buses past cer- tain predetermined points along the highway, thus indicating time. 7 in the main office the position of buses at any an

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OARING around an outlaw track in a warm-up lap, a racing driver noticed one of his front wheels wobbled dangerously. Quickly he pulled into the pit, where me- chanics found a front spindle broken. It was too late to change before the race. A few minutes later the car rolled across the starting line with the spindle welded. As the driver streaked around the course on the third lap, the welded spindle suddenly parted. His car left the track, rolling over and over. The unfortunate driver was picked out from a pile of smoking, twisted wreckage. Such an accident under American Auto- mobile Association control would never have happened, as the car would not have been allowed to start. Power to bar an unsafe car from the track belongs to a little group of technical experts who hold in their hands the lives and reputations of drivers upon the 8 on Official records re- quire strict adherence to rules under super- vision of the A.A.A. Top——-Muroc. Lake is the scene of many gruelling car tests: and new records. Above left——-Electrical timers keep an accurate check and furnish indisputable evi- dence of records. When endurance tèsts are being _ conducted, flares light the course during the night. . Hour. after hour, cars speed around: the course while AA.A. officials watch every detail of the test. Modern Mechanix

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nation’s major speedways. That’s why the “Three-A” contest board is the supreme court of the racing world, and why its deci- sions are final. Perhaps you have seen the yellow flag sud- denly raised during an exciting contest. An A.A.A. man has noticed some unforeseen danger on the track, and drivers are warned to hold their relative positions until the green flag tells them of hazards cleared. Then they Here is a battery of electrically controlled stop watches. Large charts are kept and every lap accurately recorded. Every pos- sible precaution is taken to prevent slightest error in records. May, -1938 Error is reduced to a minimum by having = electrically controlled devices do all the measuring: The in- struments are watched constantly by officials. must make a complete lap before applying a heavy foot to the accelerator. Just a short time ago, for example, a racing car broke an oil line, spilling oil on the track. Up went the yellow flag. All drivers eased their throt- tles until the green flag was raised to show the track clear. i Long before the crowd fills the grandstand, A.A.A. men have been busy behind scenes. Cars have been inspected and then im- pounded to await the starting signal. All are thoroughly examined for safety, especially front axles and steering mechanisms. Speci- fied devices such as safety arms to prevent losing of wheels, and a fire dash between driver and engine compartment, must be carried. If a car is too light for good driving, the driver may not “slug” his mount by carrying sand-bags or other weight, unless it is built into the car. The hood must be fastened securely with two straps over it. If a driver loses it during a race, he must retrieve it next lap. , The A.A.A. is the American branch of the parent association, the Internationale des Automobile-Clubs Reconnus. Racing clubs register as members, accepting its authority to rule on all mechanical phases of their con- tests. Disputes between drivers come before this court of the track for settlement. Some- times one racing pilot will accuse another of forcing him into a spin by crowding. A com- mittee hears the complaint, and if it cannot settle it, refers it to the national committee, which meets four times yearly in Washington. Six times in eight main-event races, a cer- 59

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tain driver roared across the finish line ahead of the whole field. Other drivers became suspicious of his good fortune. “He’s using loaded dice,” was the whispered gossip. Finally some one lodged a complaint with the A.A.A. Technical Inspector who then examined the car and found it well below the maximum compression ratio and displace- ment allowed by the rules. His findings gave the driver a clean slate; but if the motor had not met specifications, he would have been ruled out of the game for a year, and in addi- tion would have been heavily fined. Because the race-track is the automobile world’s greatest laboratory, official records must be made under accurate and strict supervision. A.A.A. men supervise both speed and economy races to compel rigid adherence to specified rules. A leading race driver piloted a stock car across the continent in an economy run. When the car arrived in Los Angeles, A.A.A. 60 The finish of a test tun on Muroc Lake. When a car passes the finish line officials compute records made during the run. Be- cause the race track is the automobile world’s greatest laboratory, official records must be made under accu- rate and strict super- vision. AA.A, officials supervise both speed and ecomomy races to compel strict adherence to specified rules. Be- fore the start of any tace, all cars are ex- amined for safety, especially axles and steering mechanisms. inspectors found that the head had been planed down, raising the compression ratio. The record was not allowed, and another car had to be selected, to repeat the run. It cost the manufacturer more than three thousand dollars, but it was worth it, for otherwise the record would have been open to question. When automotive engineers test their de- signs by staging transcontinental runs, usually the A.A.A. experts are called in to supervise. Not long ago an AA.A. man walked into an eastern salesroom and at random chose a stock sedan from the floor, for use ina test run. A manufacturer wanted an official test of his radically stream-lined automobile, incorporating airplane principles of design which engineers said should cut wind resistance by as much as forty per cent. Mechanics under A.A.A, supervision tore down the car selected, checked parts against stock specifications, and reassembled it. The [Continued on page 132] Modern Mechanix

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New Device Quickly Removes Hardness From Water ESIGNED to eliminate hardness in water, this bucket can be placed near any water outlet to obtain an unlimited supply of soft water. Synthetic zeolite used in the bucket, not only removes properties that go to make for hardness in water, such as lime, calcium, magnesium, etc., but it provides a water that tests have proved to be softer even than rain water. No chemicals of any kind are added for this result. In use, the rubber hose is connected to the usual outlet so that the water first goes into the pail before passing into the sink. Automatic Machine Cuts Ice Into Small Cubes HIS machine saws a 300-pound piece of ice into standard size ice cubes in about seven minutes. The cake of ice stands on its end on a small elevator. As the sawing pro- gresses, the block of ice is automatically raised about one and one-half inches at a time. The top of the cake is cut off by a hori- zontal saw to make an ice slab of the correct thickness. This slab then is subjected to the action of two sets of vertical saws, so that the ice is cut lengthwise and crosswise into cubes which then drop into the iceman’s bag, or are carried to storage by a conveyor. The clean “snow” resulting from the cutting can be used for many purposes, and is stored within the cabinet in a box which is easily emptied while _ the device is operating. The machine is en- tirely automatic and safe. Tilting Ash Tray Eliminates Fire Dangers QUIPPED with a self-tilting mechanism, this ash tray makes it impossible for a cigarette to burn down so short that the weight of the over-hanging end causes the cigarette to over-balance and fall off the tray and burn the table or rug. If the cigarette is allowed to burn for any length of time while on the rest, its heat causes a spring within the tray to expand and tilt, thus dumping the burning butt into the tray. This tray in use eliminates not only the danger of damaging furniture as the result of forgotten cigarettes, but the possibility of fire from the same eause. - May, 1938 61

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Scientist Secures Photo Of Large Sunspot Group A UNUSUAL photograph of a number of sunspots, so large that they could be seen by the naked eye when viewed through a piece of smoked glass, was recently made by Dr. J. J. Nassau, director of the Warner & Swasey Observatory of the Case School of Applied Science in Cleveland, Ohio. The big group of spots, numbering 35 in all, covered an area 120,000 miles long and 60,000 miles wide. One particular sunspot had an esti- mated diameter of 10,000 miles, surpassing the earth’s diameter by 2,000 miles. = = 120,000 MILES ACROSS Eames = ae : SIZE OF THE EARTH Dr. J. J. Nassau adjusts the telescope which he used recently to take a photograph of sunspots. Right—The unusual sun- spot photo with an earth mark to serve as size comparison. Auto Courtesy Light Devised : ETTER road manners may result if an automobile signal device recently placed on the market becomes popular. Mounted on the radiator cap or at the rear of the auto, the device enables the driver to acknowledge courteous driving on the part of another motorist by flashing the words “Thank You” in illuminated letters, which are visible night or day. A control on the dash or steering wheel operates the signal light and drivers report that passing mo- torists are first surprised, then pleased, by the unusual display of highway courtesy. Aero Experts Praise Diesels DDRESSING a meeting of the Society of a Automotive Engineers in Detroit, Mich., government aviation experts predicted that Diesel engines would replace gasoline-fueled motors as power plants for future aircraft. The almost negligible ability of Diesel fuels to burn except under the special high pressure and temperature conditions within a Diesel engine, as well as the low fuel consumption- high power rating of modern Diesels, is the basis for the experts’ forecast. According to the same authorities, the Diesel engines used in German airplanes today are accomplish- ing what enthusiastic engineers are only pre- dicting for gasoline motors five years hence. ER see If you are interested in any of the items Controlied from the dashboard, this auto signal light mentioned in this issue, send a stamped, return flashes “Thank You” te acknowledge highway courtesies. envelope for the address of the manufacturer. au a 62 Modern Mechanix

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Seeks To Found Major Silk Industry Breeds 15,000 Silkworms In Home And Perfects Reeling Machine TARTING modestly with 15,000 silk- worms, housed in the garret of his home in New York, N. Y., John Ousta hopes to found a major silk industry in the United States. He is now perfecting what is said to be the first silk-reeling machine ever con- structed in this country and with this appa- ratus and his improved methods of breeding the silkworms despite adverse conditions he feels certain an American silk industry can be built up within a reasonable time. ‘Phonograph’ Tests Mentality ESIGNED to aid psychologists in deter- mining the mental rating of patients of the crime clinic at the Institute For The Scientific Treatment of Delinquency in London, England, a newly developed machine resembles a portable phonograph in appear- ance and operation. A waxed record, bear- ing a series of small red dots, is revolved at varying speeds and the patient is required to jab at the dots with a stylus pen, the number of hits or misses serving to classify the pa- tient’s mentality. Working Steam Roller Model Pulls Two Persons On Cart TANDING only ten and three-quarter inches high with an overall length of 20 inches, a working scale- model of a steam roller con- structed by C. Hollandtrick, of Lincolnshire, England, is claimed to be powerful enough to haul a small trolley seating two persons. The model weighs 26 pounds and was constructed at a cost less than five dollars. A coal fire being imprac- tical on such a small model, the water is heated by means of a paraffin burner to create a steam, pressure of approxi- mately 40-45 pounds per square inch in the broiler. May, 1938 In America

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64 Shown below is taxidermist W. E. Eigsti, fitting teeth in a manikin of an African dog-faced baboon which, when completed, will appear as life-like - to museum visitors as the black ape and drill specimens posed naturally at his side. A wealth of detail and painstaking “be- hind the scenes” labor is involved in Prepating museum exhibits before they are placed on public view to elicit such expressions as “How natural!” and “How life-like, one would almost think they were alive!” from scores of museum visitors. The photos on this page show exhibits be- ing prepared by taxidermists at the Field Museum of Natural History in Chicago, Hil. In the photo above, a taxidermist is putting the finishing touches on seal speci- mens that were collected by Admiral Byrd’s tast Antarctic Expedition. The photo at lower left shows staff workers complet- ing a spécimen of a giant Tibetan panda, while in the center photo other staff taxi- dermists are touching up a marine exhibit made from cellulose-acetate compound. Modern Mechanix

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Gasoline Turbine Engine Perfected For Marine Use ESIGNED for marine use and developing 125 horsepower, a newly invented internal combus- tion turbine, which was recently placed on exhibition in New York, N. Y., features eight firing cham- bers and fires twice to each revo- lution of the crankshaft or four times as much as an ordinary gasoline engine. The engine is water cooled and weighs about 400 pounds, although a much lighter type is being developed for avia- tion use. The gasoline turbine engine has five rotors mounted directly on a straight shaft, three rotors being of a compression type, while two are combustion rotors. Compres- sion is caused by a cam action which is integral with the rotors, the firing and ex- pansion directed on the rotor cam serving to eliminate the use of pistons. The firing rotors are cooled by water flowing through the shaft. The oil system is of the force-feed type. The adjustable mounting of this new ultra-violet ray lamp enables the operator to direct the radiations where desired. NEW, highly flexible source of ultra- violet radiation, consisting of a quartz- tube mercury vapor arc of improved efficiency mounted within a special reflector on a por- table laboratory stand, has been developed by a well known electrical products manufac- turer. The sealed mercury vapor tube unit, which can be operated from any 120-volt or 220-volt A.C. line, has a rated operating life exceeding 2,000 hours. May, 1938 Deveioping 125 horsepower, this new- marine gasoline turbine features firing and compression rotors instead of pistons and fires four times as much as an ordinary gasoline engine. Engineers Pave River Bed S PART of ‘an extensive flood control program costing one million dollars, United States Army engineers are paving the banks and bottom of the Mississippi River in Ő the lower valley region of Louisiana with `' huge sheets of asphalt. The pavement is ex- pected to prevent erosion and under-cutting of the river banks due to the pressure of the water during periods of flood. The asphalt sheets are prepared aboard barges and, when cooled to the proper tem- perature, are placed in position by moving the barge out into'the river as the sheets are gently lowered overboard. Prepared aboard barges, asphalt sheets are being lowered onto the Mississippi River bottom (above) by U. S. Army engineers in an effort to prevent erosion caused by floods. 65

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Apparatus Takes Photographs Of Invisible Particles Top—This apparatus enables scientists to take photographs of minute particles which are invisible under a microscope. The lower photo is a close-up of the camera, stroboscope, centrifuge and lamp which are the main parts of the apparatus. Constructs Novel Altimeter UNIVERSITY of Michigan glider enthu- siast has invented an ingenious “home- made” rate of climb indicator for soaring fans. A thermos bottle, a glass U-tube, glass tubing and a calibrated scale constitute the device described by its inventor, L. D. Montgomery. Water and a small “leak” are the essential features of the instrument. Changes in atmos- pheric pressure, which are proportional to the height of the plane, are registered by changes in the height of water in the U-tube. This device, essentially an altimeter, is converted into a rate of climb indicator by controlling the flow of water by means of the “leak,” a fine capillary tube from the thermos bottle. The thermos bottle is used to minimize changes in the temperature of the water. 66 NEWLY developed scientific apparatus enables photo- graphs to be taken of minute particles of matter which are in- visible when viewed through a microscope. Although used pri- marily in the medical field, the apparatus is said to have many industrial uses. The apparatus features a rotor on which the sample matter is revolved at high speed to develop a centrifugal force of 250,000 times gravity, separating the par- ticles, and a stroboscope which rotates at 80,000 r.p.m. An elec- tric lamp and a camera are used in conjunction with the apparatus to obtain a permanent record of the centrifuged particles. Scale Device Tests Peaches DEVICE for testing the ripeness of peaches has recently been developed by ‘the New Jersey Agricultural Bureau Experi- ment Station. Heretofore, the degree of ripeness has been determined mainly by guesswork, but the new pressure tester enables the determination to be made scientifically and accurately. The tester is equipped with a sharp-pointed plunger and when the point is pushed into the peach the pressure necessary to penetrate it is registered on a specially calibrated scale. Pushed into a peach, this scientific tester has a calibrated scale that accurately indicates the ripeness of the fruit Modern Mechanix

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Miniature Home Features 35 Furnished Rooms HIRTY-FIVE completely furnished rooms, in periods, are featured in a novel Lilliputian home recently placed on exhibi- tion in Los Angeles, Calif., at a benefit staged to aid underprivileged children. The furnish- ings for the rooms were made from materials gathered from all over the world, collected and arranged for the ‘exhibition by Mrs. Elizabeth W. Larke. _ An outstanding feature of the tiny home is a grand staircase, less than four feet overall, which was constructed from an ivory fan, a tortoise shell bird cage and wood from an old walnut bed. Many of the rooms contain carved ivory statues and priceless miniature pictures. Chandeliers made from earrings and bedsteads made from fan sticks and lemon forks, as well as 25,000 other odds and ends, comprise the furnishings. . Hand Meter Tests Headlight A Kansas highway officer tests the candlepower ot an auto- mobile headlight with a portable light-intensity meter. HETHER an auto’s headlights are faulty, medium, correct or illegal can quickly be determined through the use of a new hand-~-carried intensity meter recently developed. The device is funnel-shaped so that it fits over the headlight glass in such a manner that a built-in diffusing plate directs the light rays into the meter, which is cali- brated to show the candle-power produced by the headlight. May, 1938 This photo shows only a few of the 35 completely furnished tooms featured in a novel miniature home recently exhibited in Los Angeles. Some of the tiny decorations are priceless. The young lady is admiring one of the carved ivory statues. Student Develops Explosive ENDELL ZIMMERMAN, 24-year-old post-graduate student at the University of California, is said to have discovered a formula for making a new explosive that is 53 times more powerful than TNT. Known only as RPX, the new explosive will be used in inter-planetary rocket experiments, ac-. cording to Zimmerman. A A sa NE ee Conducting chemical experiments, Wendell Zimmerman dis- covered a formula for an explosive more powerful than TNT. 67

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- TUNING UP THE F YOU, like thousands of other sensible outboard motor owners, stored your motor away last winter in accordance with the clearly printed instructions that were supplied with the engine at the time of its original purchase you need only observe a few simple, common sense “tuning up” rules now in order to insure maximum efficiency throughout the dawning boating season. The first step is to go over the entire motor, tightening all screws and nuts. If a screw does not seat properly, do not force it, but unscrew it. Then, after dipping the screw in some heavy oil, try rescrewing again, mak- ing sure that you have engaged the threads properly. Remove the spark plugs and squirt some clean gasoline into the spark plug holes. Pull the motor over by means of the starter rope’ until the oil that was placed in the cylinders during the winter has been pretty well re- moved. 68 OUTBOARD Ardent fishing enthusiasts are “boosters” of the outboard engine because it en- ables them to visit widely separated fishing grounds within minimum time. Check the spark plugs for breakage and adjust the gaps according to the manufac- turer’s specifications. Test the plugs to see if they are delivering a good spark by at- taching each plug, in turn, to a spark plug wire (grounding one wire in the case of two, or more, cylinder types) and turning over the engine to see if a “hot” spark appears across the plug points. In the event you do not get a good spark, remove the entire magneto assembly and check all wires for breakage. The coil can be given a protective coating of water-proof varnish at the same time. Take the carburetor apart, as explained in the manufacturer’s instruction booklet (if you lost yours, you can obtain a new one from the manufacturer at a nominal cost), and remove all dirt and oil. Replace the gasket if necessary, as indi- Modern Mechanix

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cated by breakage or a dried out appearance. Clean out all old grease from the gear housing, wash the housing in gasoline and check the gears for breakage. Refill the housing with grease recommended by the manufacturer. (This is probably the most important of all pre-season precautions). Having tightened all screws and nuts, checked the plugs, magneto, coil, etc., as well as cleaned the carburetor and refilled the gear housing, you are ready to mount the motor on your boat. Start the engine in the usual manner, making certain that water is running through the pump within a few seconds or the cylin- ders will crack from the heat. Carefully adjust the carburetor until you are getting maximum efficiency and smooth ‘running. Don’t “go off the handle” if the engine does not run smoothly at first, but check over all parts systematically until you locate the trouble. “Losing your head” won’t get one single r.p.m. out of the engine. Modern outboards are practically fool-proof and when they do break down it can usually be traced to abuse by the operator. May, 1938 The knowledge that the outboard motor will eliminate the tiring job of rowing back to camp helps to make the fisher- man’s day more enjoyable (top) and enables the followers of Izaak Walton to linger at the choice spots until the last pos- sible moment without fear of missing “chow.” Above-~Hun- ters, tao, find the outboard to their liking for there is nothing like the powerful “putt-putts” when it comes to traveling up- stream in a boat loaded with hunting and camping equipment. 69

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by Montgomery Mulford ` Shown at the left are reproduc- tions of three postmarks that will intrigue any collector. Top to bottom—British Post Office cover which was mailed from Turkey; an Italian postmark that served to advertise the Facist Revo- lution, and an Irish Free State postmark bearing the s Í o g a n—"Grow More Wheat”. Each year more and more nations advertise and propa- gandize by postmark. OSTMARK collecting has a number of attractive features. First of all, a number of them being elusive results in a chase which adds to the collector’s interest. Second, many postmarks are rarer than the stamps, so that they are well worth seeking. And third, the postmark shows that a letter and its stamp have done postal duty. There are many groups of postmarks to arouse the interest of the collector. The ones illustrated with this article picture some of the most interesting types. Growing more elusive, for instance, are the postmarks showing that a stamp did duty in the post office of one nation established in another. These postmarks are grouped as “offices abroad” and, in many instances, postage stamps of one country have been overprinted for such use. A pertinent example is shown in the illustration of the British Post Office cover which was mailed from Constantinople (now Istanbul), Turkey. i Various European nations have maintained postal services in other lands, these foreign offices within sovereign nations using their own postmarks and, often, their i own stamps. Thus the British-Constantinople office used postage of Great Britain, surcharged with a Turkish value. Where the prepared stamp may be fairly common, a postmark of the type shown, is not usually met with, though not really rare. Since these postmarks are not as common as the stamps in the “offices abroad” _ group, the chase for the items is in itself interesting. When one finally attains such a postmark, especially upon full cover, it is felt that the chase has been well worth the effort put forward. The pursuit of the postmark is fascinating, and might be likened to a game. The more elusive one postmark may be, the greater is its fascination. Quite often postmarks are of historical interest, in more ways than one. The “offices [Continued on page 130] 9

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A Wroueut Iron GLOBE LIGHT by George A. Smith HE beauty of this wrought iron com- bination of lamp and globe lies in the contrasting colors of the dull gray hammered iron with the more or less vivid colors of the land and water areas on the globe. Before beginning the iron work a globe should be purchased. The lamp illustrated contains a 7-inch globe which costs less than a dollar. Ifa globe larger or smaller is used, [Continued on page 126] This attractive globe- lamp can be made easily and quickly. The work ‘will be simplified if the builder will study the constructional FILE ENDS TO SHAPE data carefully before the work is started. 1" SQUARES PATTERN FOR SCROLL WOODWORKING - RADIO - METALCRAFT PHYSICS - MODEL BUILDING - ELECTRICITY - HOME AND SHOP KINKS DRILL & TAP FOR pig (-8" PIPE NIPPLE & ae) FOR SMALL LIGHT SOCKET i COTTER PIN DRILL HOLES TO ACCOMODATE COTTER PINS | HOLD CORD 5-8" TO BAND r8” Tick, HAMMERED IRON BAND WASHERS TO SUIT HAMMERED BAND IRON k li ‘tl COUNTERSUNK, : | he RIVET HOLES 7 - AUTOMOBILES - CHEMISTRY 4i

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Head on, the “Weber Roadster” has a strik- ing appearance. In the drawings below, the construction details of a simpler radiator and Above—when: pushed for- ward, the hand lever causes the idler pulley to tighten the single drive-belt, mov- ing the car. Pulling lever back applies the brakes. HERE is one definite rule to follow in making a sidewalk automobile—get your engine first and build the car around it. This applies pretty much to the wheels, too. A half-horsepower, two-cycle washing machine engine is available in nearly all sections of the country, and as these can be had second-hand at a reasonable price and have sufficient power for moderate speeds, they make satisfactory installa- tions. Herewith are working drawings of the little car owned by Richard Weber, of San Marino, Cali- fornia, which is driven by this type of motor and has proved successful for a long period. It is very easy to build. In Figs. 1, 2 and 3 are given the general over-all dimensions. Note that the front wheels have a wider tread than the rear. This permits a shorter turning radius, and brings the back wheels in close to the power unit. The engine is provided with Modern Mechanix

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groove vee a mh pan a we i =) 9" \ Ally, na RING, \ HOUSING Left—The trim little run- about is powered by a washing machine motor of one-half horsepower, which enables the car to travel about 16 m.p.h., averaging 50 to 75 miles per gallon of gasoline. Motor is connected to one wheel by a drive-belt. by Hi Sibley a kick starter, and the clutch arrangement consists of an idler pulley which tightens the single drive-belt when the hand lever is pushed forward. When pulled back, it operates the brake. Drive is on one wheel, brake on two. Hood, seat-back and dummy radiator are of galvanized iron cut as shown in Fig. 12. These dimensions are approximate as a cer- ; a RN tain amount of fitting is always necessary for RADIATOR FROM isti curved members. If you have the facilities, saN, ANUM, AND E ; j A The start of a midget auto “race”, with the Weber car in fore- ground of the lineup. May, 1938 73

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~ Lorre SAW OUT RIM FROM 3/4". PLYWOOD ENGINE G. FORD MODEL T PULLEY EE BIKE GRIP SPIDER CUT DOWN i TO FIT 12" WHEEL 3/4" PIPE aor LLL? rare iw ges Soe Se ae Soe REAR END OF CHASSIS WITH DRIVE ANDBRAKI NG ~= DETAILS —

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RADIATOR ORNAMENT CLUTCH & BRAKE LEVER the edges of the metal should be beaded. The edge of the seat back is protected with a strip of leather laced on with rawhide. It will be best to leave the cutting of the hood, etc., until the chassis is completed. U SS Ull SESE ie eee ES Several types of wheels are available for ill ces >| | small autos, being manufactured by toy | | REAR.WHEELS i makers, tire companies, etc. The original car a | dh l in the photos has disk wheels with the brake drum and pulley cast integral, and turned [Continued on page 118] FiG.3 FRONT VIEW BATTERY FOR LIGHTS 3/4" X 36" . IRON PIPE ARM OF 3/16" BAR, — ‘OR 3/8" DIAM. ROD —>+ FIG.9 DETAIL OF STEERING KNUCKLES 4“ CARRIAGE FIG.5 — FRONT END OF CHASSIS SHOWING STEERING ASSEMBLY SECTION TURN TO FIT. OF AXLE 3/16" STEEL BAR ` WHEEL BEARING ne 73

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TEST YOUR MODEL in this WIND 4" X 3/4" STOCK TOP PLATES OF 48" 3/4" X 3" STOCK A gA CORNER POSTS OF TOP SILLS OF ANY SCRAP LUMBER “SS iS ay, St ~ CELLULOID PSS OR GLASS I il i i l 1 f l WINDOW 1 | t K 5" 8 FLOORING TUNNEL CABINET Shown above and at right are the general constructional de- tails of the cabinet, honey- comb air-straightener core and air pass of the novel model plane wind tunnel. The cir- cular sketch shows how the honey-comb core is constructed by notching and inter-locking strips of sheet metal. The sketches on the opposite page show additional details of the air pass construction as well as complete details of the dyna- mometer assembly. Practically all parts are made from easily obtained scrap materia ls. N RESPONSE to numerous requests re- ceived during the past few months, Mopern MecHanix is herewith reprinting plans and details for the construction of a miniature wind tunnel for testing model air- planes. This article, in its original form, appeared in the MM “Flying Manual,” 1932 edition, and was written by Dick Cole. Many experimenters have undoubtedly tried to test their models in the blast of air 76 “> WALL BOARD 3/4" FLANGES - NAIL OR SCREW TO END FRAMING oe 18" X 46-2" TO FIT INTO END OF CABINET VVVVV VV VV T EY ———— cv WY¥VYVVVVVVYVY vy sa | OLDERORWELD ¥~ AIR PASS OR CONDUIT (HEAVY TIN OR SHEET IRON) AIR-STRAIGHTENER CORE (SEE DETAIL BELOW) DETAIL OF CORE (SHEET METAL) from an electric fan, but such tests are highly unsatisfactory for the reason that the wind created by the fan is a mass of whirling currents—a miniature tornado. To test a model plane successfully, it must be placed in a flow of air that is moving with equal velocity throughout its entire cross-sectional area, and the air stream must be free of whirling eddies. How this ideal condition is brought about is shown in the sketch illus- Modern Mechanix

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AIRPLANE ADJUST TO HARDWOOD END BLOCK FITS INTO AIR PASS. Wem \ STRAP. IRON BRACKET TO ZERO DRILL FOR FAN BRACKET 16" DIAM, FAN POSTAL SCALE RECORDS "DRAG" DETAIL. OF BLOWER FAN INSTALLATION trating the complete wind tunnel assembly. -The principal parts of the model wind tunnel are a partially closed cabinet, an air- straightener honey-comb core, an air pass, a dynamometer assembly and an ordinary electric fan or a kitchen ventilating fan, such as is shown in the sketches. The electric fan sends a blast of air through the air pass and its only outlet is through the honey-comb air-straightener, which serves to emit the air in an even flow, creating the eddyless condition required to test the model plane. The model is mounted on a dyna- mometer, being completely exposed to the air flowing through the honey-comb core. The lift scale and drag scale, as shown in the sketches, will give a direct reading showing the effect of changing the positions of the [Continued on page 122] May, 1938 BRING POINTERS il 3 _—— NOTE; ALL arms EVERS OF " ALUMI~ EET RUBBER BINDER DIMENSIO; AS FROM NS CENTER To CENTER POINTER LIGHT SPRING ES oe! a se? i THUMB NUT TENSION Ap- JUSTMENT 374" Wo, BRACKE a p SCREW TO FLooR DYNAMOMET; STAND DETAR a, 77

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Handy Wire Brush Wringer Fits Any Paint Can PIECE of spring wire bent to the shape shown in the drawing makes an efficient paint brush wringer. Instead of the usual method of drawing the brush full of paint across the edge of the can and having some of it run down the side, the wire across the center of the can makes it possible to pull the brush over it and have all the excess paint drip back into the can. When the wire is to be used on another can, wipe it off thoroughly’ and it is ready for use with a different color, When preparing the wire, bend it so that when it is fastened in place, the ends spring closed against the rim.—A. H. Handy Kinks For Star Drills RESHARPENING STAR DRILLS S RIGHT aN w NAIL HANDLE we CHISEL CUTS SS HOSE COVERING. - OPTIONAL |; NU! STUCK DRILLS ey DRILL F THE shank of a star drill is marked off in -inch and half-inch notches, it will always indicate its depth in the hole it is making, eliminating the necessity for meas- uring drilling progress with a ruler. Either Roman numerals or just scratches can be used to indicate depth. When taking read- ings, allow for shortening of the drill by sharpening. A drill often becomes wedged tight unless constantly rotated and the hole cleared fre- quently. When it does become wedged, some- times it is necessary to use a wrench to loosen it. Ifa hole is drilled through the upper part of the shank and a large nail or bolt inserted, this “handle” facilitates the turning of the tool and its removal from the hole when it is necessary to clear it of dust and chips. When sharpening star drill, grind the edges so that they do not taper up to the point, as shown in the drawing.—Andrew Vena. 78 BEND PIECE OF WIRE THUS SS SLIPS OVER RIM OF CAN DETACHABLE BRUSH WIPER SAVES PAINT Awl Aids Difficult Painting N ORDINARY awl with one end cut off as shown in the drawing, is an invaluable aid while painting small objects such as handles, knobs, etc., when there is nothing on the object which will serve as a handle as the painting is being done. The point of the awl is pushed into the object until it supports it firmly. The awl with the object attached can be held in the hand firmly while the painting is being done. The end of the awl should have been sawed off flat so that it will stand up by itself while the paint is drying. If an awl is not available, a large nail can be shar- pened so that it will duplicate the end of the awl. This pointed nail then can be forced through a block of wood and it will be as self- supporting as the awl—G. B. Harran. SAW THIS ENO OFF

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4 SANDPAPER GLUED TO BOTH SIDES SANDPAPER GLUED TO WOODEN DISK AND FASTENED TO FACE PLATE CIRCULAR PIECE = OF SANDPAPER -3 GLUED TO END DECORATIONS APPLIED TO METAL 7 SANDPAPER Is WRAPPED AROUND STICK AND GLUED — HOLD IT IN PLACE WITH STRING UNTIL DRY i t SANDPAPER GLUED TO THREE SIDES GLUE SANDPAPER AROUND DOWEL AND TIE WITH STRING The usefulness of sandpaper can be multiplied many times by fastening-it to various-shaped strips of wood. Be sure to use a good grade of glue. Several sizes of each design will be found very helpful to the amateur craftsman. 79

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z sias $ * ate Fe

Above is shown the finished craft ready for a thrilling journey out on the pond. At the tight are construction details of the car lock.

r 7 . z 3" yee = NOTCH SEAT 4x 12 V4" LAG ; AROUND POST ~j- TAPERED vie SCREW- : N HEAD CUT OFF

SEAL ALL JOINTS WITH COTTON TAPE LAID IN PLENTY -OF MARINE GLUE , HE principal defect of back-yard built boats is / that they leak, and_ the skipper frequently comes : - If all joints are carefully 4B. SASH home with wet feet. But here is a craft just as dry | fitted, this small craft will WEIGHT as the living room floor, and it is easy to make. not leak. A coat of paint 7 Ordinary pine lumber is used. The bottom consists wili improve its appearance. ANCHOR = of two nine-inch boards with a chine piece all the ae: way around except at the bow, where the stem is to fit. With the aid of a plane and plenty of sandpaper, the chine and bottom boards are fitted perfectly flush. Binding tape augmented by a liberal amount of marine glue used over all joints will keep Junior’s shoes from becoming even damp. Next install the side planks and transom, using cleats where indicated, with tape and marine glue between. A batten over the tape and glue along the center of the bottom keeps this joint water-tight. Seats are supported on cleats, as shown, The oar-lock is a 14-inch lag screw screwed into the gunwale and the head sawed off. The end should be filed smooth and rounded. For the oar use a piece of

i

34-inch by 12-inch pi bout fi feet | ith | Cet i j ‘4 “ANC! Yy ‘2-Incn pine abou our feet long, wt “ mu t, n t . a wooden blade nailed on. It should be slotted about i 18 \|| one inch for the oarlock pin. S i i A Give the inside a coat or two of gray floor paint, ny =

and the outside white with green trim. Assuming the joints are well fitted this little skiff should be water- tight after a few hours in the pond, 80

INBOARD PROFILE & PLAN

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A MODEL AIRPLANE CLEAT DIAPHRAGM HIS small and easily constructed jig saw, built from some scrap wood, a discarded auto horn, and part of an old carburetor, has been found to cut balsa wood accurately and quickly and has proved entirely satis- factory for the model airplane worker. By using very fine scroll blades, this saw will _ run on six to eight volts from a toy trans- - former for a considerable time without overheating and will cut one-half-inch balsa cleanly and quickly. . The horn must be of the vibrator type, preferably with the commutator bolted to the diaphragm. Remove the diaphragm and the commutator. Cut a triangular piece from the diaphragm embracing two of the bolt holes on the rim and one for the commutator as shown in the photograph, The lower blade grip is constructed from one pole from any of the cheap makes of knife switches. This is cut in a manner similar to the grips on an ordinary coping saw and bolted to a short piece of sheet metal which [Continued on page 124] Easy to construct, this jig saw will be found very helpful to the madel airplane builder, It will cut balsa up to one-half an inch thick. Six to eight volts from a stepdown transformer will power it. Marwood by Gardner JIG SAW — 14"4- EXACT DIMENTIONS DEPEND UPON SIZE OF HORN USED ONE END FLATTEN & DRILLED INVERTED CARBURETOR AUXILIARY VALVE CUT DOUBLE | NOTCHES IN Í SPARK PLUG CAP | EET METAL T TO SHAPE MANNER OF i NOTCHING Ye” BLADE GRIPS “ CUT OUT TRIANGULAR SECTION FROM HORN DIAPHRAGM 81

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OMEONE has described certain articles of furniture as possessing the quality of | coziness. This quality is amply evinced in the small gate leg table, for it is both cozy and comfortable, and, furthermore, because of its attractive turning, it is a highly deco- rative piece of furniture. The person who is interested in wood turn- ing will undoubtedly find a friendly challenge in the construction of this article. Aside from the skill necessary to turn out six duplicate legs, the craftsman will not encounter any unusual complications in its construction. All construction is obvious and not in the least complicated. In making this small gate leg table, place emphasis upon all those important “touches” which put good furniture across. Such “touches” include the proper dulling of edges (as indicated in the plan), the use of wooden pegs to both strengthen and lend a quaint crafty appearance to all mortise and tenon joints, and finally a proper finish to give life and warmth to the completed article. 82 (afd eck Ye cia ERA Cy aes ee If each part is shaped carefully, final assembly will be very simple. Ithough almost any wood can be used, either walnut or cherry is suggested. A thorough sanding before any finishing is applied will give a more pleasing appearance to the completed project. Plenty of rubbing with a soft cloth will give a warm and attractive luster to the finish.

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a

Any one of a variety of different woods can be used. It is recommended, however, that either walnut or cherry be used. Note that the sizes given below are of the finished stock. Stock should be cut slightly larger than these dimensions to make allowance for dressing and working to actual size. Turned Members: 2 pieces, 144”x142”x17%” (end posts) 2 pieces, 114”x142”x1958” (gate posts) 2 pieces, 144”x112”x16%” (gate pivot posts) Because it is necessary to duplicate exactly the turning of all these members, it is suggested that the worker cut an exact and full size pattern of the turning before starting the operation. With this pattern as a guide, the craftsman can readily obtain the exact shaping desired. After the turning is finished, cut mortises and tenons, as indicated in plan, on various turned members. Mark and cut half lap cut-outs on ends of outer gate posts. Feet and Top Cleats: 2 pieces, 114”x2”x8” (feet) 2 pieces, 114”x144”x4” (top cleats)

Square to specified sizes. Mark and cut mortises. Cut pattern for foot shaping as indicated in graph detail. Mark this shaping on two opposite faces of each other. Cut and finish to exact shaping of pattern. Round under edge of top cleats. Assemble turned posts to feet and top cleats. Secure joints with glue and insert wooden pins while assembly is being held together under clamp pressure. These pins should be per- mitted to protrude 4” from surface. They are rounded off to give proper quaint pegged effect. [Continwed on page 122]

goer CLEAT Before turning the legs the builder should make a full-size pat- tern. With this as a guide, no difficulty should be experienced in turning out exact duplicates. After the turning is finished, the mortises and tenons are cut. The dimensions of the curves shown in the detail can be varied to suit individual taste. JOOS co

TOP CLEATS ~ PARTS S&5A

ER A = a el i TE oe ; Zz PARTS 7-7e 6 2 ele A me) es DOWEL HOLES é € A is N : "DEEP F - PIVOT : DOWEL PARTS 4 £40 —? a a Ys DIAM. :

Ss

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RE ADERS of preceding articles on microscopy are now familiar with the parts and operation of a microscope, and have made studies of pond life, insects and other intro- ductory matters. They have made temporary slides and a few whole mounts that require little if any technique. So now is the time to take the next and the biggest of all steps in microscopy, and to learn how to cut thin sections and make really professional and permanent slides that can be preserved, sectioned, stained and mounted in balsam. -This is a sizeable job and the whole story cannot be told in a single chapter. In the present installment we shall go into the details of cutting thin sections, and other stages in microtechnique will follow along in succeeding issues. Sectioning—the cutting of thin slices—is necessary whenever the material to be ob- served under the microscope combines thick- This is the eighth in a series of articles published by MODERN MECHANIX on this fascinating sub- ject of microscopy. Previous articles are as follows: April" Documentary Evidence’—A study of the characteristics of handwriting and typewriting, and how the microscope is used to track down law breakers. ‘March—"The Silent Sherlock”—The microscope and its use in present day crime detection. February——* ‘Finger . Prints in Fur’——How the microscope is used by the fur industry for identifi- cation purposes. December——"'Hitching a Microscope to Your Camera’’—How a camera can be used with a micro- scope to preserve the wonders seen by the eye. November—"The Autumn Empire of Insects”— The thrills of big game hunting are revealed under the lense of the microscope in the study of common insect species. October-—"Microscope Reveals Mysteries of Life in Water’—-How to delve into the wonders of nature with a microscope as your „magic key to the store- house of life at its conception. HOW TO CUT Homemade microtome is easy to build and use to get thin sections. At the upper left is pictured a cross section of a lily flower bud showing all the structural parts of a typical flower. At its right is a longitudinal section of a dandelion flower. Above is shown the hand microtome described in the text. ness with opacity, and this is usually the case. It is possible to secure surface views of such objects as skin, liver or heart, and of stems, leaves, stones and minerals; but generally it is impossible or inadvisable to try to make permanent mounts of most of these, and no information at all is obtained of the internal Modern Mechanix

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MICROSCOPE by Julian D. Corrington, Ph. D. Plasticene _ models to show the planes to be fol- lowed in cutting sections. - Radial object at left and bi- lateral at right. In the latter, card- board strips represent the three planes. structure or of the kinds of cells that make up plant and animal organs. Slices thin enough to permit the use of transmitted light are necessary and so a com- plicated technique of procedures has grown up to serve this need and to prepare the beau- tiful and permanent slides that are in com- mon use in high school and college courses in biology. If you have never seen this sort of slide we suggest that you purchase one from a supply house or dealer so as to have it as a model in making your own. Ask for a cross section of basswood or other tree stem or of lily flower bud, double stained. On the blank glass slide has been placed an ex- ceedingly thin section of the material, per- manently preserved against decay and stained with various dyes to give color and contrast: to otherwise almost transparent structures. The section has been rendered translucent by means of an oil and has been placed in Canada balsam and then a cover glass added. After thorough drying to harden the balsam, the slide was cleaned and labeled. It is such a slide that we are going to make, taking one of the major steps this month. Advanced and detailed studies may require May, 1938 SECTIONS FOR YOUR s ct oN sections that are not only very thin, but of a known and uniform thinness, and hence there have been de- veloped a number of types of precision in- struments known .as microtomes, from the Greek words small, and to cut. Some use a knife carrier that slides back and forth in a slot; others operate on the rotary principle and are quite similar to the rotary meat slicer to be seen in a meat market. Some one, in fact, referred to this style of micro- tome as “a glorified meat slicer.” Ma- chine microtomes cost from fifteen to several hundred dollars. For all ordinary and prac- tical purposes, however, a hand microtome, as described in this article will do the trick and can be made by anyone familiar with the use of tools. First, though, there is the free-hand method of cutting sections which employs no micro- tome at all, and whether or not you plan to operate a microtome you should know and practice this system. Every microscopist worthy of the name should go through this step in his training and acquire a bit of the necessary manual dexterity, so often lacking in this machine age. Recommended as practice material at this season of the year are leaf buds from trees, particularly the larger types, such as horse’ chestnut. The knife may be either the old- fashioned razor, as shown in an accompany- ing illustration, or a safety-razor blade held in a carrier with folding handle—an object commonly sold in the five and ten cent stores. The stiff type of blade is better for our pur- poses than the flexible one. New blades are readily inserted in the carrier when the one in use becomes dulled. Hard woods 85

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WIRE FILED WOOD BLOCK. 6" xX 3" xX 3" oy ra TEE AY I a fw m a m a — THREADED BRASS DISC ROD -THREADED- BRASS BRASS OR C.R.STEEL TUBING Above are details for constructing mi- crotome. At upper right is shown the method of cutting free-hand sections as described in text. will ruin a razor for sec- tioning purposes after only .two or three slices, softer ones after a dozen or so. Other kinds of tissue that cut more easily may yield as many as a hundred; but in any case the time ar- rives when a change of blade or a sharpening of the old-fashioned razor is indicated. Crushed, torn or otherwise mutilated or dis- torted sections are as certain as they are undesirable when a dull blade is used. Now for the job. Sit at a table so that both elbows may be supported on the table top, or sit in a chair away from a table and hold the elbows pressed firmly in to the sides. Hold the bud between thumb and forefinger of the left hand and knife in the right. Place the knife blade upon the left forefinger, flat, cutting edge toward the body, the finger hori- zontal. The motion of cutting is that of par- ing, not that of whittling; i.e., the blade is pulled along the forefinger, toward you, the finger serving as a guide. A long sliding cut is made, starting with the heel of the razor and passing to its toe, coming along the fore finger toward your body. f Have both the bud and the razor blade wet with water and cut slowly and carefully at first, increasing the speed as skill develops. Practice in cutting sections thinner and thin- ner until extremely thin ones are obtained. Keep knife blade and bud surface wet. Avoid wedges—thicker on one edge than another. ` As fast as sections are cut, float them off the knife into a shallow vessel of water, or transfer them from knife to water with a camel’s hair brush. The fingers are too in- delicate for this, and sections should never be touched by the hands. After a number have thus been executed, reject all but a few of the very best and thinnest, saving these for further attention, as described later on. The hand or well microtome consists of a hollow tube as a holder for the object to be cut. 86 GLASS The bottom of this tube is raised very END VIEW gradually by turning a screw, in that way raising the object a given and uniform amount with each turn, permitting sections of known and even thinness. The cutting platform or surface is a very smooth one, as plate glass, and the razor blade is guided on a slanting stroke across this surface. After each slice the screw is turned a designated amount and another cut made. Sections are then floated off in water, as before, and only the best ones retained. A block of hard wood such as maple, about 6” long and 3” square in cross section is bored part way down the middle from one end to receive and hold tightly a length of rather heavy-walled brass tubing of approximately 34” bore. The rest of the length of the wooden block is drilled to receive the threaded brass or steel rod, hereafter re- ferred to as the screwrod. The threading should be carefully done and have as many threads to the inch as possible. If you can- not do this for yourself, have it done, or pur- chase and use an ordinary bolt, diameter about 1⁄4”. Next braze a thick brass disc into the lower end of the brass tube, then drill and tap it accurately in the center to receive the screw-rod. Again, if you do not have access to the proper machinery, a nut for the bolt can be centered in the tube end and held there with plastic wood. The tube may now be driven into the block, plugged end inward. Insert in this tube a shorter length of brass or steel rod which makes a neat sliding fit; [Continued on page 134] Modern Mechanix

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as ee GAS TANK FORD T FRAME MEMBERS ENGINE CONTROLS STRAP IRON SUPPORTS 2" X 3" OAK CROSS PIECE "DRILL EA. SIDE Loc DOG ATTACHMENT (DOGS NOT FNS CARBURETOR 1925 FORD T COOLING FAN FAN GUARD SEE DETAIL OF FAN MOUNT , 1” X 5" DIAM. FAN PULLEY (STARTER — PULLEY MOUNTED DIRECTLY BEHIND) OLD AUTO WORM STEERING GEAR FORMS REDUCTION DRIVE CRANK ARM SHAFT zy SHAFT BEARINGS TO SUIT ; SF : ik 3/8" STEEL PLATE $ m . (BOLT TO FRAME) X 4 r _ V4! STEEL PLATE (WELD OR BOLT TO FRAME) \. =a Ne nis DRILL TO SUIF g SAW BLADE HOLES CROSS HEAD GUIDES a (FORD T STEER! BABBIT TO SLIDING FIT TAP TO SUIT THREAD FORD T TIMING GEAR BUTTS UP AGAINST | "40 PIPE SHOULDER ON SHAFT E TE HANDLE F OR D $o 3 ao LE AND TIE-ROD DETAILS OF Keyway OLT EN = ijan GROSS HEAD OF THE GENERAL ASSEMBLY . fear AL : at X 6" X12" STEEL Salvaged parts from old autos and a oe second-hand motorcycle engine are used to build the timber drag-saw shown in the above photo and sketches. c t NY home workshop me- chanic can rig up the power-driven timber drag-saw shown in the accompanying photo M and sketches. Economical to oper- BLY ate, the saw features sturdy construc- tion and will stand up, well despite hard daily usage. The frame is made from chassis members One of the pulleys is used to start the of an old model T Ford, riveted or bolted engine, a rope being wound around it and the together in the form of a triangle. The power pulley spun by pulling heavily and quickly is provided by a second-hand motorcycle on the rope end. The other pulley, by means engine fitted with an extended drive shaft to of a belt, is used to rotate a fan that serves which two five-inch pulleys are attached, as’ to cool the engine. The fan is mounted on shown in the sketches. [Continued on page 124] May, 1938 87

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EMERGENCY REPAIR FOR BROKEN ROD TIP MZ} SQUARE UP ENDS AND DRILL HOLE WITH SMALL DRILL — (NO 50, 55, 60) Meese ac 1) l: T ZZA TAPER T SECTION OF NEEDLE -COAT SURFACES WITH CEMENT AND PRESS TIGHTLY TOGETHER ih a | | epee re i i P} WRAP TIGHTLY WITH SILK THREAD AND APPLY CELLULOSE CEMENT OVER WRAPPING Rg E E : Boor LACE f TO TIGHTEN MALE \ COATED WITH FERRULE, DRILL HOLE THROUGH METAL END-\_ ABRASIVE, DRIVE A PIN OR NEEDLE S POLISHES EINE INTO CORE OF WOOD NL ISHING can probably be classed as one of the most universal and cosmopolitan of all outdoor sports. It is quite safe to say that LENGTHS OF ENAMEL LINE it plays a part in every man’s life at some BUNG EROM time or other, perhaps beginning with a hick- WET WARD ORE ory branch, grocery store cord and a bent TO TIGHTEN À Le MOSQUITOES pin, and leading up to the prized possession EE NS KITA Toit of a “Thomas” or “Hardy” rod, taper lines, AECONOEIAEAME PEACE T and a vast collection of lures and flies. POSITION UNTIL WOOD DRIES $ à 3 $ $ OUT AND GLUE RESETS Fishing—angling—is becoming a truer sport every year. Our forefathers fished solely to get fish. We of today fish for the joy of outwitting the fish with artifice. Our forefathers’ tackle consisted of a solid bamboo “pole” with a length of 10-cent A Pop a fi {tn "yo wy wt linen line tied to it—no reel; eyed hooks J det ea a A SPLIT PIECE at 5 cents a dozen, a can of worms and a nein RUBBERS FELT . IN rusty nut fora sinker. The angler’s tackle of DRAPED OVER CREEL, Fon SPE KEEPS FISH FRESH DRESSING TO LINE IN HOT WEATHER OLD NAIL FILE FINE EMERY IDES TO MAKE TO KEEP BROOK TROUT IN GOOD. CONDITION CLEAN IMMED- IATELY UPON CATCHING -WIPE DRY AND ROLL EACH FISH SEPARATELY IN WAXED PAPER Broken rods can be quickly repaired by splicing the break in the manner described in the details at upper right. Lower illus- trations show how a loose fertule may be tightened simply by heating it over a canned heat flame. To ward off annoying insects the fisherman may attach lengths of old fishline to the brim of his hat. A quick way to apply dressing to a fishing line is to split a piece of varnish-rubber felt to form an applicator. To keep fish from spoiling, clean and wrap in waxed paper. 88 ; Modern Mechanix

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today can easily run into three, or even four figures. However, to gain full enjoyment of angling as a sport, it is not necessary to invest a large sum of money. Perhaps a $10.00. domestic rod will not handle a $2.00 “level” line with the same nicety that a $150.00 tournament rod will handle a $15.00 double taper line, but, when the two outfits are put to actual use on a stream, maybe the $12.00 outfit will out-fish the aristocratic equipment. It really is the man at the butt-end of the rod that decides the issue. It is not the intention of this article to give a treatise on the art of bait and fly casting, but rather to pass along to fellow anglers a few little kinks that may aid them in gaining a fuller enjoy- ment of their favorite sport. What can be more annoying than to break a flyrod tip section far from camp? However, a satisfactory repair job can be made right on the stream if the angler carries some simple equipment with him. This consists of a packet of needles of assorted sizes, a tube of celluloid cement, several small twist drills—say, No. 50, 55 and 60—and a spool of strong silk thread. To proceed with the repair job, the broken ends R 2gn x TAPER LEADERS ; MADE OF SYNTHETIC V124. SILK WORM GUT AND TREATED WITH AIRPLANE DOPE SERVES VERY WELL FOR DRY FLY CASTING SOAK GUT AND FORM KNOTS- TIGHTEN AND PULL x ETHER BLACK HACKLE FLY REMODELED INTO ROCK WORM - VERY EFFECTIVE "WET FLY" IN SLIGHTLY DISCOLORED WATER ; Ml WRAP BODY WITH ACO ALTERNATE TURNS OF RIND BLACK AND YELLOW YARN “LAMPER" BEL OR ANGLE WORM MADE OF BACON RIND SPLIT BACK FIN AND TAIL TO IMPROVE WRIGGLING Every fisherman derives more satis- faction from the sport when he is able to land his catch with lures of his own creation. Several effective lutes are shown above. A black hackle fly can be made into an effective “wet-fly” by wrapping the hook with alternate turns of black and yellow yarn. A good lure for all game fish can be made from bacon rind as shown in the lower detail. VERY EFFECTIVE FOR WALL~EYED PIKE IN AT- LANTIC WATER- SHED SPOON KY > GANG HOOKS GOOD LURE FoR PARTLY CON- CEALED UNDER Fins ALL GAME FISH May, 1938 89

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While this fish was taken with an expensive rod, there is just as much fun landing your catch with a bamboo pole. are first squared up, then the most suit- ably sized drill is used to bore a hole in the core of each broken section. This can be done by rolling the drill in the fingers, or a pair of pliers can be used. Next, the ends are beveled off accurately. A needle is now selected which fits tightly into the hole. The point and eyes of the needle are broken off, and the steel body is inserted in the hole. Before bringing the joining surfaces together, coat each one with celluloid cement. When the cement becomes “tacky”, press the surf- aces tightly together. Wait for a few minutes for the cement to set, then wrap the joint with silk thread and apply several coats of cement to the finished wrapping. Set the rod section in the direct sunlight, and fill up the _old pipe, and when the smoke is finished, the rod will be ready for use. Loose, shaky ferrules on a rod are a nuis- ance. The remedy is simple. Fill the female ferrule with water and boil it carefully over an alcohol flame or over the camp stove. This will soften the glue. When it resets, the ferrule will be firm. A drop of thin, water- mixed glue dropped into the ferrule will aid. 90 A loose male ferrule can be tightened by driving a pin or a needle into the wood. Line guides and tip should be kept polished to provide a free-running line. An ordinary boot-lace, coated with a fine abrasive, will do the trick. Fine “grinding in” compound or pumice will serve. For an extra high polish use “Fuller’s earth” or a silver polish powder. Undoubtedly a fly lights nicer on the water if a taper leader is used. Taper leaders made of silk worm gut are expensive. Syn- thetic gut, which can be bought in 30-yard coils, is taboo to the chronic fly-caster. It frays—takes on a feather edge—and soon be- comes water-soaked. However, satisfactory taper leaders can be made with synthetic gut by following the directions in the accom- panying drawings. Three coils of synthetic gut in assorted sizes will make enough taper leaders for several seasons. The simple secret is to treat the gut with airplane dope or celluloid cement. This must be done only when the leader is perfectly dry. There is an added satisfaction to an angler to outwit game fish with lures of his own [Continued on page 130] Women, too, find angling a sport packed with thrills. fishermen don't go out after fish—they go Modern Mechanix True fishing!

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CIGARETTE BOX HAS TRICK LID À the method of attaching the hinges is the (a same. The latter have nothing in common Ne with usual hinges, but consist of pieces of stiff brass wire with looped ends which are anchored with pins at the four corners of both box and lid. A study of the illustra- tions will reveal the operating principle. After assembling the box, saw notches at [Continued on page 126] CIGARETTE BOX WITH LIO r é 7 MONG the different types of con- | iS i 5 7 IN ERONT AND £4 tainers designed for holding ARE AS SHOWN AND ARE : : : CUT OPPOSITE TO EACH OTHER cigarettes, this one has real novelty in addition to practical usefulness. The lid cannot be raised by a direct up- ward pull, but either side can be opened at will, for the box is con- structed with hinges on both sides. Without a close inspection the method of operation is puzzling to the average ob- server. The box in the illustrations was made of 14-inch “tempered” pressed wood, which is par- ticularly hard, and has inside dimen- sions of 3%4x2%- inches. A larger box to hold handker- chiefs, jewelry or other articles is as easy to make and END OF BOX SHOWING HOW WIRE HINGES ARE ATTACHED CUTTING, \ NOTCHES FOR HINGES SHOWING HINGES BENT IN CIRCULAR LAND "U" SHAPED N LOOPS ON ENDS Constructed from a sheet of one-quarter-inch pressed wood, the novel cigarette box shown at the left has a lid that can be opened from either side, but not by a direct upward pull. Any home craftsman can build this simple box after a study of the photographs - and sketch, which amply il- THE FINISHED BOX lustrate the construction de- se tails explained in the text. May. 1938 91

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A simple rack will sup- port the tomato vines when they are heavily laden with fruit. Any scrap lumber will be satisfactory. A coat or two of paint will make its appearance much more pleasing. To insure a good tomato crop, fertilize the seedlings generously so that they will become tall and spindly. Scoop out earth at one side and bend the stem down into cavity and cover it with earth to within a short distance of the end. , “PART OF STEM i i BECOMES ROOT This sweet-pea trellis of galvanized pipe and wire can be pulled up and moved to a new spot each season. When the vines have withered the trellis can be pulled up and stored to make room for any. other plants. TA a w 92 Modern Mechanix

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This easily con- structed wood trencher makes uniform rows when it is pulled along a string stretched along the path to be fol- lowed. Dimensions can be varied to meet the individual builder's needs. When the task of caring for the lawn becomes tire- some, considerable work can be eliminated by care- SHAPE OF ful planting of annuals. TRENCH The taller ones should be placed near the house. HOME GARDENER VERY amateur gardener has been confronted with at least one of the problems solved here, such as the burden of caring for the lawn after the spring enthusiasm fades. An old-fashioned flower garden, once established, does not re- quire exacting care. You may have old trees whose foliage is spindly—feed it vitamins When a drain slope is as great as 45 degrees, rocks should be embedded in the earth. An incline using plain sod should not be permitted to exceed 30 degrees. 3”X 12” TILE PIPE A three-inch drain pipe set into the ground is a convenient means of feed- ing tree roots. The pipe can be filled with fertilizer and then filled regularly with water. In some loca- tions this is the only way trees can obtain sufficient moisture to exist. May, 1938 through drain tile, or water through a perforated pipe that reaches the deeper roots. The seed trencher is easy to make, and the sweet-pea trellis a great convenience. Tomato vines pro- duce a surprising crop when started right in youth. And that dried out and trampled terrace can be greatly improved with a rock garden. 93

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CHOOSE THE RIGHT BRUSH O YOU really enjoy the creative work of © wielding a paint brush? It can be just as interesting and as pleasurable a recreation as any other workshop hobby. One de- terrent to “having a good time while decorating” is the use of unsuitable materials. Of course it is neces- sary that you work with a good quality of paint, enamel or varnish, but just as im- portant is the choosing of a brush that is exactly suited to the job. This informa- tion comes not 94 i Modern Mechanix

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from the brush manufacturers but from skilled profes- sional decorators, who know how to turn out first class work because it is a matter of pride and repeat business. First, they say, pay no attention to the size or shape or weight of the handle, nor how the brush bal- ances in your hand. If it is of a reliable make, the manu- facturer has provided a handle that is adequate in all respects. The important part to examine is the bristles. You will not find good bristles in cheap brushes. Master decorators consider it a worthwhile investment to pay up to $5.00 (and sometimes three times that amount) for a brush with which to do their best class of work, so it is to be expected that only very inferior ` work can be done with one purchased for 10c. A good rule is to use as fine a brush as you can afford for the quality of work to be done. With practically all types of brushes the quality is dependent on two points: first, the bristles should be springy, elastic and full of life. They will not spread paint well if they are coarse and stiff, and are likewise unsat- Opposite page—Several types of brushes needed for all- around house painting. Left—-A sheet of cellophane makes an excellent moisture-proof holder for a brush. Top of page —The correct way to hold a brush. Right—To paint the inside of a narrow space where the hand can not reach, screw an old brush to the end of a broom handle as an extension. May, 1938 ` . 95

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isfactory if they can be bent in any di- A new brush, can be rection without resistance. Secondly, pressing it ee ea examine the ends of the bristles by fan- ack of the hand. The ning them out between the fingers. If bristles should be s ee % es springy and full of life. each is well “flagged,” or split into two or more smaller branches, they will do good work. The flag ends will enable the brush to hold more paint and will spread it out better. Choose a brush of the correct size and type for the work you wish to do. If you are not sure about the one to use ask the dealer. The bristles should not be too thin or scanty. ` While a narrow brush is desirable for narrow work, it may leave markings when brushing out the paint on a wide surface. The length of the bristles is important and the longer they are, the better the brush. Then notice whether the bristles are set in glue, rubber or cement. If the brush is of good quality, either of the three types will be satisfactory for its purpose, but with a cheap brush the setting will allow occasional bristles to loosen throughout its life. A glue-set brush will not be satisfactory if it is to be put in water, while one set with ce- ment should never be used with a finish containing alcohol, such as shellac, or in Close inspection of brush bristles quickly reveals the presence or lack of “flag ends.” Their presence is an indication of quality. 06 Modern Mechanix

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Above—Use a coarse comb to work the cleaner deep into the heel so that every trace of paint is removed. Above right—The result of improper clean- ing and care of what was a good brush. the more volatile solvents such as are contained in quick-drying lacquer and lacquer thinners. The rub- ber-set brush may be used _ for all around purposes and will prove most generally suitable. There may be a few loose bristles in the new brush, even of good quality, and it is a good practice to flick them out beforehand by slapping the bristles across your fingers a num- ber of times. If trouble from loose bristles is expe- rienced later, it may be due to lack of care in cleaning and preservation. For outside painting jobs most master painters use flat brushes in several widths, with black Chinese bristles set in rubber. For general work you will need one three or four- inches wide, and for sashes and trimming a narrower one with a longer handle (known as a trim brush), either round or oval so that it will carry more paint. With these, as well as with brushes for interior work, you should have a flat duster about four inches wide to clean up the work ahead of the paint brush. While a duster is not absolutely necessary, the quality of your work will be greatly im- proved. For enamel and varnish some painters use a good grade of black Chinese bristles, but when questioned they usually admit that for particular work their preference turns to a May, 1938 Cleaning a brush imme- diately after using it will keep it in first class con- dition for years. Below —A large coil spring will hold the tip of the brush in the paint. soft flowing Fitch brush. Bear and ox hair also come in the latter class. While for ordi- nary painting you will use a square-end brush, varnish and enamels should be flowed on, and for this reason the chisel end is usually chosen. For ordinary work use one about three inches wide, and if possible have on hand smaller brushes for narrow work and trimming. For walls select a four-inch Chinese bristle; floor can be handled nicely with a two and one-half-inch flat or oval, the latter being given the preference. In general, use a brush to suit the size of the surface to be finished, and do not try to use [Continued on page 132] 97

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YX 7/8"X 15" -SIDE RUNNER

ASS Bette me im AN 72! sa. E HOOKIN DETAIL BLE TO DASHBOARD ul

SIDE ELEVATION Because this table folds compactly out of the way it can be carried in the car at all times and is in- stantly available when needed. Scrap lumber and one hinge are all that is needed for its construc- REAR ELEVATION tion. If made as de- scribed, it is very rigid. 98 etn aya au

A UTILITY TABLE FOR THE AUTO HIS folding table. is ready for use at any time and when not needed can be folded compactly and kept in the trunk or under the seat. Although designed for holding a portable typewriter, it can be used as a picnic table, or to prop up a book or magazine for easy reading. It hooks in the glove compartment of the dashboard on almost any popular priced car when the compartment door is dropped down out of the way and the real weight of the table and anything that may be placed upon it is carried by a verticle post that rests on the floor of the car. The table top is made of a piece of one- quarter-inch plywood, 13” by 16”. Two pieces of 7%” by 1” wood, 15” long are nailed to the under side of the top, flush with the long sides of the top. The ends of these two reinforcing strips are flush with the front edge of the table. On the under side of the top and across the ends of the reinforcing pieces, at the back of the table, is nailed a piece of 14” square wood, extending from one side to the other. When the table is complete this will prevent it from sliding too far into the dashboard compartment opening. Different types of hinges are used on these compartment doors, depending upon: the make of car. Whatever the type, some pro- vision must be made for the table to hook into [Continued on page 128]. Modern Mechanix

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Short Cuts For The Motorist File Refaces Pitted Auto Valves TORN or pitted valves can be refaced easily and quickly by the method shown at the right, when the usual refacing machine is not available. The only tools necessary are a medium-fine file and a valve grinding tool. To use the device, place the valve and file block in the position shown, insert the valve grinding tool in the EAT es || valve head and give the valve twenty or thirty turns, | °° NMS me or until a smooth face is obtained. Then remove the TE N ene ee block and grind valve with grinding paste—K. F. Keith. Lm ee Baking Soda Simplifies Nut Removal WITH PLIERS JUST BEHIND TERMINAL é ORROSION often holds the battery connector so Ss tightly to the terminal that damage may result if it is forced off. The connector usually can be removed easily and safely by placing about a teaspoonful of ioe bicarbonate of soda on the terminal and then pouring on BOILING 4 | eee sufficient hot water to dissolve the soda. Leave the solu- VATER A PEE tion on and around the terminal for about a minute and the corrosion will be softened. The terminal then can be removed without trouble. Be sure that none of the soda solution gets into'the battery acid.—G. V. Dwyer. Screw Driver Aids Spanner Use ANY times when a special nut is to be turned, the correct size spanner wrench is not avail- able, the wrench being either too large or too small. When confronted with this problem, a screw driver or another spanner will be useful. The screw driver can be inserted between the nut and the over-size wrench. Hold the spanner in one hand and the screw driver in the other, and force both Pee $ FORCE SCREW DRIVER Ze BETWEEN WRENCH together and exert pressure on the nut at the same Ke AND NUT TO REDUCE time. The flat back or handle of another spanner WRENCH. TO! CORRECT may be found to fit the gap perfectly.—G. V. D. : -LEAVES FROM. OLD FORD J Spring Leaves Loosen Bolts SPRING USED AS LEVERS HEN wheels have not been removed for a long time, occasionally the nuts will be found to be so tightly fastened to their bolts that the usual brace carried in the car for removing them does not have sufficient leverage to do so. When this is the case, two leaves from: an old spring placed in the position shown in the drawing will eliminate the difficulty. The additional leverage obtained in this way will be found sufficient, in most cases, to loosen the most stubborn nuts, even those held in place by rust—G. V. D. May, 1938 99

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How To Reduce The Hum NOT CRITICAL REPLACE THIS CONDENSER AS TO HUM WITH NEW ONE OF I6 MF. AC. OR WHEN HUM I$ HIGH DC. LING B+ HEATER STAING -ÀA- — RES EE TERESI CHASSIS {ST A-F REDUCING HUM OUTPUT TUBE eo ee VOLUME CONTROL GRID LEAK .25 0.1 ME MEG 125 MEG CHASSIS CHASSIS TO c- c= In Radio Receivers EARLY all the hum in radio receivers is. traceable to the audio amplifier. The hum prob- lem is acute at present, because it costs more money to reduce it to a satisfactory level than most set manufacturers are willing to spend. The critical listener, on the other hand, is willing to spend a dollar or two if he can reduce hum. The following suggestions have been found to be very effec- tive in many cases. In ac-de sets, hum increases with time in many cases because the second filter condenser ages. The remedy here is to replace this condenser even though volume and sensitivity appear normal; the usual connection of this condenser is shown at A of the attached sketch. It is well to insert grid filters to reduce hum, regardless of the type of set. The connection of a grid filter is shown in B of the at- tached sketch. Locate the grid terminal of the first a.f. or output [Continued on page 128] Shielded Lead-In Gives Reduction In Noise Level PECIAL aerials for reducing man-made interference are usually costly and many times are of no value. One scheme which has been used with excellent suc- cess is to use an aerial of ordinary, simple design and connect it to the set with the lead-in shown at the right. In the sketch is shown the lead- in wire proper that connects to the set and to the aerial wire in the ordinary manner with the usual insulation that surrounds the wire; this insulation should be as heavy as possible. The copper braid covers the insulation; and does not connect to anything. Merely slip it over the heavy lead-in wire from end to end and clip it short at both ends so that the lead-in wire protrudes at both ends. After the braid covers the wire, cover the entire length with paraffin so that the braid 100 COPPER BRAID TO COVER INSULATION does not ground to anything in wet weather. One effect of using this lead-in is to reduce pickup by the lead-in to nearly zero, which reduces noise and increases the directional properties of the aerial. Modern Mechanix

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GROUND The fused line filter in use takes up . very little room and gives protec- tion against blowing house fuses. XPERIMENTERS and radio servicemen will find a fused line filter a handy unit to have for radio testing. By using this unit, the possibility of blowing out the house fuses is eliminated in case of a short in the radio under test. The line filter also eliminates very efficiently, common interference present in the power line. The filter uses two large size chokes, and four condensers connected in a highly efficient filter circuit. A ground must be connected to the terminal provided, to obtain the best re- sults, The dual outlet will permit the test of two devices, or the extra outlet near the radio for the soldering iron. The fuse may be quickly replaced in the novel terminal block. In locations where line noises are a source of interference, the unit may be installed for permanent use. The line filter will work on any a.c. or d.c. power line circuit up to 250 volts, PARTS LIST 1 Wooden cabinet with carrying handle 1 Power cord and plug 1 Dual outlet receptacle 1 Little fuse holder and five ampere fuse 1 Ground connector REC chokes C Paper condensers, 1 mfd., 600 volt peak May, 1938 An under view of the filter baseboard showing the parts. The fuse is in the tube at the lower right side. The two choke coils are mounted im the center, and condensers at sides. Note the wiring simplicity. 101

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METER TESTS READING LIGHT A round typewriter ribbon box makes a satisfactory holder for the light meter. With this device it is easy to test the light-giving. qualities of a reading lamp. Of simple construc- tion, it is even easier to use and gives satisfactory results. The triangular open- ing can be made by scratching dimensions N in wax over the bòt- en tom and filling it with acid. After a few min- utes, it will fall out. S THE light of your reading lamp bright enough to prevent eye strain? You can easily make sure, and test all of the other lights in your home and shop, with this simple and easily constructed meter. It has a small triangle-shape window through which can be seen a piece of sensitive photo paper, and a piece of darkened “tint” paper. Allow light from the reading lamp to fall on the meter (just as with the electric brightness meters) and note the time required for the photo paper to darken to the shade of the “tint? paper. If this is more than two minutes, the light is not bright enough for normal reading pur- poses and the bulb should be replaced with one of a higher rating. A round typewriter-ribbon box makes a good case for the meter; if you wish, the’ printing on it can be removed with acetone. To make the window, a good method is to The round disces of sensitive paper are made by soaking ordi- nary bromide enlarging paper in a five per cent solution of potassium metabisulphite. flow the inside of the. box with candle wax or paraffin, then scribe the outline of the opening with a sharp point. Cover the bottom of the box with diluted muriatic acid until the triangular piece falls out, leaving a win- dow with smooth, even edges. The round discs of sensitive paper are made by soaking ordinary bromide enlarging paper in a 5 per cent solution of potassium [Continued on page 120]

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| Piece! 3rd PRIZE ODERN MECHANIX - ss SECTION i PAGES 103-116 FIRST PRIZE—$15—'"'Seeing Eye to Eye”, by Raymond Rabino- witz, 911 Walton Avenue, Bronx, N. Y. Showing that the simplest objects sometimes make the most interesting pictures. A single spotlight gives the shadow effect, 5 x 7 camera. SECOND PRIZE —310—"Gingham Silhouette’, by Pastor H. Schaller, Tomah, Wis. Made by laying piece of muslin on negative in enlarger. A clever stunt that has many possibilities. THIRD PRIZE—35.00—to Warren Stormont, 217 East Pine St., Springfield, Ill, for an un- usually good candid stage shot made with an ordinary vest pocket Kodak; 1/10 sec. at f. 5.6, super-sensitive pan film, developed in D-76. FOURTH PRIZE---$5,00——“Friends”. by Nathaniel Haven, . 1370 East Avenue, Rochester, N. Y. An out-of-the-ordinary animal picture. Made with a 31⁄4 x 414" Graflex on portrait pan film, 1/100 sec. at f. 4.5 in dull light. The pose and the expressions are very good. FIFTH PRIZE—35.00-——‘Chapel at Sunset”, by John H. Crowe, 3230 Bancroft Hall, U. S. Naval Academy, Annapolis, Md. A filter does help! Retina camera, 35 mm. super-sensitive pan film, 1/50 sec. at f, 8 with medium yellow filter, Taken at 6:00 P, M. MONEY FOR YOUR PICTURES! Get busy with your camera and send in unusual pictures of people, shouid be accompanied by the following data: make and size of animais, machines, trains, airplanes, ete, Each month we will pay camera, type of film, and how developed and printed, lens opening $15 for the best picture received from readers, $10 for the second and shutter speed, and lighting conditions. Wrap all prints care- choice, and $5 each for the next three selections. Prints should fully and include postage if you want them returned, Address all be glossy, as large as possible up te 8x10 inches (although a contributions to Fnorography Editor, MODERN MECHANIX. 1501 smali, clear phota is more desirable than a big, fuzzy one) and Broadway, New York, N. Y. 103

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THE “TIN CAN SPECIAL’ 174" x 178" Parts BRASS LENS r. 172" DIA. HOLE. INSERT RED CELLULOID WINDOW GROOVES FOR NEGATIVE HOLDER AND DIFFUSION GLASS, MAKE TWO PIECE OF ADHESIVE TAPE J IR HOLDER The view finder of the camera provides a mounting for the enlarger’s lens-filter (top sketch), construction of which is described in text. Center sketch—-Construction details of the grooved blocks, which accommodate the negative holder and diffusion glass, as shown in sketch at top right. Two pieces of hinged negative glass comprise holder (above). 104 from an old folding camera plus ~ M a tin can and a few n easily obtained inci- dentals are all that are required to con- struct the photo en- larger shown above. va IDE OF la NEGATIVE BOX HÒLES FOR MOUNTING OPENING FOR NEGA- TIVE HOLDER AND DIFFUSION GLASS Ri NEGATIVE HOLDER SCREWED TO S 7 EGATIVE BOX HERE are probably few MM readers who do not have an old Kodak or other kind of small folding camera laid away in the bottom of a drawer about the house. In most cases, these have long outlived their usefulness, but the author found an old and battered Kodak No. 2, with its lens and bel- lows still intact, and considered the idea of making an enlarger out of it. A few scraps of wood and metal, an old tin can, and a piece of glass resulted in a rather nifty-look- ing piece of apparatus which surprised its not too hopeful builder by turning out fine 8”x10” prints from negatives as small as those used in the popular miniature cameras. With a photoflood as a light source, the printing time of the home-built enlarger is as fast as that of commercial enlargers with Modern Mechanix

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GROUND GLASS -SCREEN BOX CUT OFF TO TAKE ASSEMBLY NO. I 1/8" WIDE SLOT FOR DIFFUSION GLASS A Practical Photo CAMERA—WITH BACK AND ALL EXTRANEOUS Enlarger Coon o O much faster lenses, while the quality of the prints leaves lit- tle to be desired. When one considers that a mechanically flexible and rugged job can be made for a ridiculously small amount of money and work, there seems to be no reason why any camera enthusiast should not make his or her own enlargements. , The horizontal type of construction was used because of its inherent stability and simplicity. In the instructions that follow, it should be remembered that the dimensions given in the drawings are for the Kodak No. 2 folding camera. The necessary modifications for a camera of different size can be readily made. Some minor “operations” are necessary on the camera itself. The back of the camera is removed and can be discarded, since it is not used in the enlarger. Make sure, how- ever, to salvage the little red celluloid win- dow, as it will be useful in making the lens filter, which is placed before the lens when sizirig the image on the printing paper. The camera should now be opened, and all ex- traneous parts removed from the base. This includes the distance scale, the tripod socket, the closing catch, and all miscellaneous rivets and screws except those which hold down the track on which the lens mount slides. Drill four holes, one in each corner of the base, for holding down the camera. Wood screws are driven through these holes into the wooden baseboard assembly, as sketched above. The bottom block of this as- sembly should be sand-papered on its sides and bottom, since it slides on the enlarger base, as the photographs and sketches show. The total height of this whole assembly is such that the lens is on a direct line with the center of the easel. The view-finder on the camera provides a convenient mounting for the lens-filter, May, 1938 LENS BOARD SLIDE TRACK SCREWS TO HOLD CAMERA PARTS REMOVED CAMERA MOUNTING WOOD BASE ASSEMBLY _ SANDPAPER SIDES AND BOTTOM ENLARGER BASE TO SLIDE WITHIN RUNNERS ON EASEL The sketch at top of page shows complete details of the camera mounting on the wooden assembly base. Above-~Completed easel and enlarger baseboard with camera mounting slide- guides. A tin can serves as lamp housing for enlarger (below). _ since it can be swung around in and out of position. The small right-angular box hold- ing the ground-glass screen is sawed off flush and then filed clean. Short lengths of brass rod are then soldered on the screw and nut 105

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The cover of the tin can lamp housing is cut out, as shown in sketch at left, after which the housing is soldered to the negative holder box, making a firm, light-tight as- sembly. Construction details of the easel and baseboard assembly are shown in the sketch at lower right. FOLD BACK ALONG THESE LINES AND SOLDER TO BACK AT NEGATIVE BOX portions as shown on page 104. The front piece is cut short and a small e hinged optical ou negative holder own above. he spring- as a handle for the Bolden LAMP HOUSING AND BOX ATTACHED vane of thin sheet brass is soldered to it. A one-half-inch hole should be made previous to soldering, and the red celluloid window inserted after soldering, so that it will not be burned. When soldering the brass rod onto the rear section, care should be taken that too much heat is not applied as this piece is made of zinc, and melts very rapidly. The rod is used as a handle to swing the filter in place before the lens. The author found by experiment that the ` best compromise between maximum and minimum enlargement size was secured when the negative was placed about three inches back of the normal position used for taking pictures with the camera. This allows the entire length of the lens track to be utilized. It was therefore necessary to add a box-section to the camera. This section contains grooves into which the negative- holder and the diffusion glass are slid in posi- tion. Dimensions for this box are shown on page 104. The box should be made of thin sheet brass or galvanized iron, so that soldering to it is easy. It should be bent into shape, and a rectangular hole cut in the top. This is the opening for the lens-holder and diffusion glass. The grooves to accommodate the negative holder can be cut.in pieces of one- fourth-inch Masonite by a routing tool in a 106 zi- on 3 BASEBOARD AND EASEL OF 3/4" STOCK. GUIDES AND BACKSTOP OF 1/2 MOLDING OR QUARTER ROUND drill press. This is the best method for cut- ting straight grooves. The grooved pieces should be screwed to the inside of the box as shown on page 104. The negative-holder consists simply of two pieces of negative glass hinged together with a short piece of insulating tape or surgical adhesive, as shown in the sketch on page 104 and the photo above. Negative masks up to the 244”x314” size are cut from black paper. When folded up, the negative- holder is fastened on top with an ordinary spring paper fastener, which also serves effi- ciently as a handle. The diffusion glass is a piece of flash glass of the same dimensions as the negative- holder. Its use is most essential, since even illumination of the negative is impossible without it. The diffusion glass slides into place behind the negative-holder in the grooved slots within the negative box. Flash glass and negative glass can be purchased for a nominal sum from any camera supply shop. The 5”x7” size is best and it is easy to cut to pieces of the proper size if the following [Continued on page 120]

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How to improve pictures by control- ling color of light that reaches film, ECAUSE of the current widespread in- terest in color photography, there is a general impression among amateur photo- graphers that the “color filters” they see advertised so widely are exclusively part of the process of making colored pictures. This isn’t so. From the amateur standpoint “color filters’ are much more important for the making of black and white pictures than colored ones; in fact, the only two color films available for amateur use do not require lens filters at all. If this sounds a little confusing, let us consider the general nature of light and it will all clear up quickly. What we see as white light is actually a mixture of the colors of the rainbow, appear- ing in this order: violet, blue, green, yellow, orange and red. Next to the violet there is also ultra-violet, and next to the red, infra- red (heat rays), but both of these extremes are invisible to the eye. However, the ultra- violet strongly affects all photographic films and must therefore be remembered, while the infra-red registers only on very special FILTER FACTS AND FACTORS ae Above: An X1 (pale green) filter, used with Panatomic film, gives correct “color” balance to this charming scene and helps to bring out the clouds in the back- ground. Left: Without a filter, the clouds in this pic- ture would be completely lost, and the outline of the girl would merge with the sky. The use of a K2 (medium yellow) filter saves the scene. plates, and for all practical purposes can be ignored. When we speak of the “color sensitive- ness” of films, we refer to their ability to record these varying colors as different gradations of black and white on the eventual prints on white paper. For in- stance, the various films bearing trade names ending in “chrome” or some varia- tion thereof (technically, these are “ortho- chromatic” films), are affected by the rays of the spectrum from the ultra-violet through the violet, blue, green and into the yellow. Red light doesn’t register on them, and red objects therefore come out black in the print. For the same reason, these films can be opened and examined in a dark room under a red “safelight.” 107

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These three pictures graphically show the value of lens filters. he view above was taken on a dull day with regular super- sensitive panchromatic film, 1/50 second at £.14, without a filter. The heavy clouds in the sky are barely perceptible. Films of the “pan” type (“panchromatic”) respond to the entire visible spectrum, from the ultra-violet up to and including red, and therefore they register red objects as gray tones of varying depth; also, they must be opened only in complete darkness, as no “safelight” is longer “safe” for them. How- ever, regardless of the type of film, they still are most sensitive to the ultra-violet, violet and blue. Sky light is especially rich in these colors, a fact to be kept in mind. Photographers use cameras to make per- manent records of what their eyes see, but unfortunately, the color sensitivity of the human eye does not coincide with that of films. The eye is most sensitive to green, less responsive to blue and violet, and totally blind to ultra-violet. Thus, a landscape that appears gorgeous to the eye because of rich green foliage and blue sky turns out to be a very disappointing photograph when made on ordinary film. In the black and white print the trees and grass look too dark, the sky too. light. This is easy to understand now, because we know that the ultra-violet, violet and blue light of the sky registered much more strongly than the green of the 108 fields, throwing the photographic picture en- tirely out of balance with the visual picture. To restore this balance, we must restrain the powerful blue rays without affecting the other colors; for this purpose we put a piece of colored glass or other transparent sub- stance in front of the camera lens, and we call this attachment a “filter.” The name fully describes the action. Light rays of any desired color are allowed to pass through to the camera, while others are en- tirely or partially absorbed, and therefore have no effect on the film. There are dozens of different shades of filters, intended for This is the same scene, taken a few seconds later with a K2 yellow filter, 1/50 second at f.11. fairly well. The clouds now show specific applications in many photographic fields, and their study is an extremely in- teresting one for the advanced experimenter. For the amateur, however, one, two or at the most three filters will take care of all ordinary requirements in pictorial and land- scape work. Any object will appear colored if by its nature it eliminates one or more of the com- ponents of white light. Grass appears green, for instance, not because it reflects green but because it absorbs blue on one side of the Modern Mechanix:

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spectrum ‘and red on the other. A red filter looks red because it absorbs blue and green. A piece of glass which holds back only blue light looks yellow to the eye because it passes red and green, and a mixture of these colors becomes yellow. It is obvious from the landscape problem that a yellow filter would have saved the picture by restraining the sky light. The yellow filter, in different depths, is unquestionably the most useful of all. It is in- valuable for outdoor scenes in which the sky shows prominently, because in re- straining the ultra-violet and blue of the actual sky, it makes white clouds stand out beautifully. A yellow filter in many cases means the difference between an ordinary snapshot and a prize-winning salon mas- terpiece. The “Kl” is a pale yel- low filter and is used when a short exposure is more important than a high degree of correction. The “K2” is the most popular and widely used filter in photography, and brings out clouds more definitely than the Kl. When used with super-sensitive panchro- matic film in daylight, a very close approxi- mation to true orthochromatic rendering of the subject will be obtained; that is, all colors will be registered correctly. It can be used very successfully with any of the “chrome” films. The “G” is a deep yellow “contrast” filter, and cuts through atmospheric haze effectively. It is also useful in providing good contrast between snow and shadows in snow scenes. i The “XI” is a pale green filter designed to give complete color correction with super-X panchromatic and Panatomic film in daylight. Such occasions arise, for in- stance, with flowers containing a mixture of red, yellow and green. The XI is also helpful in making photos of a person’s face against the sky. Under artificial light, the X1 is used with super-sensitive panchromatic film for complete correction. The XI cannot be used with other than pan type films. May, 1938 Still the same scene, but photographed through an “A” red filter, 1/50 second at £.7. The sky looks almost black. The X2 is a deeper green filter, and is used with super-X and Panatomic films for correct color balance in black and white with arti- ficial light. It has no use with daylight. The “A” filter is red, and is of special ad- vantage is recording clouds against the sky, making the latter come out almost black. Pictures.taken in full sunshine with this filter sometimes have a night-time appear- ance. Some startling effects can be obtained with this filter if it is used carefully. A second feature of the use of a yellow filter is the better detail recorded of distant objects. During the summer, distant hills appear somewhat hazy because the haze (which is due to fog-like accumulations of moisture) scatters blue light and tends to blur scenes seen through it. However, it [Continued on page 120] 109

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GLASS CUTTER EMBOSSES PRINTS An ordinary glass cutter supplies a convenient method of embossing the border of prints, Do not apply too much pressure to the cutter. SPRING SPEEDS CUTTER When trimming prints, the cutter blade action can be speeded up considerably by using a spring to raise the blade, as shown in the photograph. CARD SIMPLIFIES FOCUSING al STRAP HOLDS TRIPOD A white card ruled with black lines as shown in the A book strap fastened to the tripod as shown in the photograph and attached to a flashlight, simplifies photograph becomes a convenient handle. It then focusing when a ground glass is used. can be carried like a suitcase. 110 : Modern Mechanix

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CAMERA FANS q FILE DECORATES BORDER A raised design on the border of prints can be obtained by placing the edge of the print on a file and rubbing the paper with a hard object. STRING AIDS PAPER REMOVAL A piece of string fastened to the top of the box containing printing paper, and passed under the pile, simplifies removal of one sheet at a time. S CAMERA IDENTIFICATION TONGS MADE FROM CLOTHES PINS By fastening a piece of adhesive tape on which is By sharpening the points of spring clothes pins, printed the name and address of the owner, to they can be used as print tongs. An ordinary file the inside of a camera. it can be identified if lost. or sanding wheel quickly shapes the required points. May, 1938 111

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-|PORTABLE SAFELIGHT T FREQUENTLY is necessary in the darkroom to look for something on a shelf or under a table, and because sensitized paper or negatives are in the open, the room light cannot be turned on. An ordinary flashlight fitted with a red filter will prove valuable under these circumstances. The “filter” consists merely of two layers or common red Cellophane, the kind used for wrapping gift packages. Un- screw the head of the flashlight, remove the lens, and use this as a pattern in cutting the Cellophane, as the photo FTER a spare corner of the cellar was walled in for a darkroom, considerable trouble was experienced by a camera fan in keeping chemicals sufficiently warm during cold weather. Two inexpensive devices found in the house solved the problem. For print developer trays, an old electric stove that cost only $1.25 new proved perfect. It raises cold developer to 65 degrees in about three minutes. The tray is left on the stove, 112 DEVELOPER HEATERS shows. In reassembling the parts, put the red discs on the inside of the lens, so that they will not be torn when the flashlight is being used. It is advisable to test this light by letting it shine for about 15 seconds on a piece of film. Develop and look for signs of “fogging.” Above: Tray on electric stove. Left: Developer tank with immersion heater. and the latter is turned on occasionally by means of a push-type line switch to keep the liquid warm. The heat is never needed long enough to damage the enamel on the tray. Developing tanks for cut film were most easily kept warm by means of an immersion heater originally used for shaving purposes. It was found necessary to tape the top tightly with adhesive tape, to prevent the developer from seeping into the heating unit. Modern Mechanix

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ROM a ten-cent mirror you can make a picture frame that is distinctive and at- tractive. Remove the backing and the metal or wood surrounding the mirror, and with a pencil mark out the picture opening on the varnish layer that protects the silvering. GLASSLESS NEGATIVE HOLDER FRAME IS OF 1/4" BRASS ANGLE SOLDER HERE IN ALL CORNERS INSERT 174" X 178" BRASS ANGLE -BUTT JOINTS SOLDERED May, 1938 NOVEL MIRROR PICTURE FRAME Around the opening draw any decorative de- sign desired. With a chisel, razor blade or similar tool, remove the silvering and its pro- tective varnish from the picture opening and decorative areas. With black or colored lac- quer, paint over the cutaway areas, with the exception of the picture opening. Usually this requires two coats to produce a solid color, When the lacquer is dry, place the pic- ture in position, return the mirror to its original frame or put it in a new one. HOTOGRAPHERS are well acquainted with the disadvantages of making en- ‘largements from negatives enclosed in the usual glass frame-work. Dust and lint must be continually removed from the glass plates ` if spots on the finished prints are to be avoided. Unfortunately, there is no substitute for this type of holder when using roll-film negatives and large cut-film negatives be- cause of the constant danger of buckling. However, with cut film in the smaller sizes, from 21⁄4” x314” to 4”x5”, the glass-less holder illustrated here has been found entirely prac- ticable. Hardly any buckling is noticeable, and the problem of dust and lint is reduced to the absolute minimum. Such a holder for 344”x414” film is shown here. The longer sections of the frame should fit snugly in the enlarger slide. 113

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DEVELOPING OUTFIT. FOR CUT FILM ERE is a developing box that will make your film develop- ing hours a pleasure. Besides being a decided convenience, it will put your negative making on a systematic basis, with the re- sult: BETTER NEGATIVES! To have perfect negatives from Lanes BOX PAINTED x INSIDE AND OUT WITH NSS ACID RESISTING BLACK PAINT 2 OR3 COATS by Keith Swanson Left—Set-up of the fin- ished box in the dark- room. Water runs in through one pipe at the right end of the box, and out through another pipe in the upper left corner. Be ` low—-This developing outfit is a very simple wood-working project. Minor leakage at the joints is not important, =" as the box is kept qin a sink anyway. OUTSIDE EDGES ROUNDED FOR LID TO WORK FREELY LIGHT BREAKER STRIPS 1172" X 14” ALL WOOD : ZA] Tag THICK, BOX X P j FASTENINGS Í cS fice NAILED the developing angle, we must develop at the correct tempera- ture for the correct length of time, all the time handling our negatives carefully to avoid any accidental scratches. A system such as here described will pay for the time and effort put into its construction if it saves one negative from accidental ruin. The box is made of wood .and contains three metal developing boxes for three solu- tions: the developer, the chrome alum hard- ening and stop bath, and the hypo bath. These three tanks are supported upon a wood subpanel so that water may flow around the tanks for cooling purposes. A hinged lid, in conjunction with lightbreaker strips, makes the inside of the box absolutely dark 114 when the lid is down. Thus, after placing of the film in the developer, and the lid closed, the darkroom lights may be turned on and other work done while the negatives develop and fix. Regular Kodak film developing hangers are used, which, when used with the No. 1 developing box, will handle any cut . film size up to 4x5 inches. To complete the negative making, another developing box is used for washing purposes. The setup in the writer’s darkroom is shown in the photo. If the darkroom is in a cellar and tends to be cold, warm water can be cir- culated in the box to keep the solutions at the proper temperature.

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“Amateur Photo Puzzlers In this department the Photography Editor will answer any question or problem relating to cameras of alt types, enlarging, printing, developing, taking pictures, and the various phases of home movie making. È When sending questions to this department, be sure to include a stamped, addressed envelope, so that we can answer directly in case space dors not permit publication of the question an this page. Photography Editor, Modern Mechanix, 1501 Broadway, New York, N. THE MM ENLARGER The MODERN MECHANIX enlarger described in the March issue has proved very popular with readers. The only part of the construction that seemed to cause any trouble at all was the rheostat. The drawings were perfectly clear, but evidently the 1000-ohm coil of nichrome wire called for in the description is not available in many parts of the country. This rheostat can be dispensed with alto- gether and replaced by a second photoflood bulb connected in series with the bulb in the enlarger itself; directly across the terminals of this second bulb, connect an ordinary single-pole, single-throw snap switch. The extra bulb should be mounted under the enlarger table and enclosed in a light- tight box of plywood or tin. When focusing with the enlarger, keep the snap switch open. This places the two bulbs in series and makes both of them burn with the approximate intensity of an ordinary 60-watt lamp. The enlarger head thus remains cool. After the image on the enlarger easel has been focused and framed correctly and an exposure is to be made on a sheet of paper, simply snap the switch closed. This short-circuits the second photo- flood bulb and causes the bulb in the enlarger to come up to full brilliancy. Incidentally, this arrangement will greatly increase the life of the photoflood bulbs beyond their rated two hours. Judging from the correspondence the enlarger article pro- duced, there must be thousands of old lenses in attic and ‘cellar junk boxes. As the article stated, any. lens of at least 514” focal length can be used. However, the focus- ing arrangement ‘does not permit the use of very long focal length lenses such as made for old-time 5x7 and 8x10 view cameras. The limit is a 64%” lens. The actual speed of the leris is of comparatively little importance, as is the condition of the shutter mechanism. In fact, a shutter is not required at all and if an available lens of suitable focal length happens to have one, simply set it for time and feave it open. A lens having a speed as slow as £.8 will be found quite satisfactory; of course, faster lenses up to £.4.5 or £.3.5 will permit shorter exposures to be made, especially with dense, over-exposed negatives. EXPOSURE IN ENLARGING OPERATIONS Many inquiries are received by the photography editor about the length of exposure necessary in enlarging opera- tions. It is utterly impossible to give any specific figures for any particular enlarger, as the exposure time depends on all of the following factors: the density of the negative, the speed of the lens, the degree of magnification, the type of enlarging paper and the type of developer. Photogra- phers who are just beginning to do their own Processing should carefully study the article on pages 104, 105 and 106 of the April, 1938 issue of MODERN MECHANIX. (This also appears in the new PHOTOGRAPHY HAND- BOOK). This article describes the approved method of making test strips to determine correct exposure. USING HYPO A question that pops up in the photography mail every day is this: “Can the same hypo solution be used for had negatives and prints, or is it desirable to have separate attles 7 „The answer is simple. The same hypo can be used, pro- vided the developer is a non-staining type. The only developer of this kind still in general use is known as “pyro” and is found only in darkrooms of commercial photographers. Practically all present-day developers of the fine grain type are non-staining in action. It is highly advisable to filter the hypo solution after it has been used with negatives and before it is used with Prints. This filtering can be done through a wad of ordinary ahsarbent cotton, placed in the neck of a glass or enamel funnel. 116 Send all inquiries to the i CUT FILM IN PLATE HOLDERS I picked up an old 4x5 plate camera in very good condi- tion at a very low price. A number of holders intended for glass plates came with the outfit. I do not want to use glass plates, because of their weight and fragility. Is there any way of revamping these holders so as to make them take cut film?—J. P., Chicago, III. No revamping cf any kind is necessary. You can buy cut film sheaths made especially for this purpose. These are simply stiff pieces of metal with rolled up lips to accom- modate the cut film. The whole sheath is then slipped into the plate holder, just as if it were a glass plate. DEVELOPING OLD FILM In cleaning out a desk drawer, I came across a roll of film taken about two years ago but never developed. Do you think it worth while to have this processed?——G. C. Flushing, New York. By all means haye the roll developed. Films have been known to retain their images for many years. DIFFUSING SCREEN What materials do you recommend for use as diffusing screens in front of floodlights using the small size photo- flood bulbs? I have tried tracing cloth, but it seems to cut the light down quite a lot.—A. H., Bronx, N. Y. Any diffusing screen will reduce the effective i to some extent. Tracing cloth is widely used b tough and can be rolled and unrolled easily. O ing paper is also good, but only for temporary silk is excellent. A large handkerchief makes a diffuser, as its bound edges resist tearing. In all advisable to mount the diffusing screen a few inche of the bulbs, to avoid danger of fire and to prov circulation of air. SELF-TIMER FOR CAMERA SHUTTER I would like to make pictures of my shop, but I'd like to be in them. I’ve tried long strings attached to the shutter and other stunts, but they haven’t worked so well. ce you suggest anything in this regard? —J. L., Lawrence, ass, What you want is a self-timing attachment, to fit +: release of your shutter. There are two types: one w delayed spring-action, the other by air-compression Both are satisfactory. You can buy them from any c supply firm. The “delav” action is adjustable up to one minute, giving you plenty of time to get into the before the exposure is made. MODERN MECHANIX AWARDS $40 EACH MONTH FOR BEST PHOTOS SUB- MITTED BY READERS The editors of Modern Mechanix distribute $40 in cash awards each month to the five persons who, in their opinion, submit the best pictures suitable for publication in the Modern Mechanix Photography section. Full particulars regarding these awards will be found in this issue on page 103.

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Cosmic Ray Dynamo Theory Advanced By Scientist Where do cosmic rays come from? What is the source of their enormous speed? Contin- ually raining upon the earth from “somewhere outside,” these fast-flying bits of electricity form a real brain teaser for scientists. For nothing which moves as fast has yet been created by earthly means. To say that cosmic rays come from giant elec- trical dynamos in the heavens sounds a bit naive, doesn’t it? Stated in those words it reminds one of the hypothesis that the planets revolve about the sun on (invisible) spokes. But when put in the precise language of physics the “cosmic dy- namo” theory is quite sound and has been sug- gestéd recently by a Swedish physicist, Prof. Hannes Alfven of Uppsala University. The rain of electricity from the cosmos, and the current of electricity running through your lamp, attain their energy in very much the same way, according to this scientist’s picture. Both derive their power from whirling magnets. Have you ever watched the giant machines in an electrical power plant? One marvels at man’s ability to create these harnessed monsters which supply his vital needs of heat, light and power. Ponderous whirling magnets, driven by high pressure steam or by the fall of water, force particles of electricity to stream through wires and serve us at every turn of our material life. To jump from the power plant to whirling magnets in the heavens may seem a bit fantastic, but such a jump was made by the Swedish physicist (although he doesn’t say so) with per- fectly good scientific justification. For, like our own earth, stars are known to be magnets. And the very same electrical reasoning which applies to dynamos in power houses applies to the in- conceivably huge heavenly bodies spinning for- ever in the immensity of space. The double star is a type of cosmic dynamo which Prof. Alfven discusses. Two stars revolv~ ing about each other can generate as much as a million million volts according to his calculations. This enormous voltage exists in a region of space between the stars. Electrical particles (cosmic rays?) which happen to be in this region are thrown out with speeds practically equal to that of light. NOTICE Changes in the make-up and title of this magazine, designed to make your favorite publication better than ever before, will be- come effective with our next issue. Be sure and reserve your copy now. Our new name will be—“MECHANIX ILLUSTRATED,” “POLISHINGS A CINCH with DU PONT POLISH” Now you'll find it easier, quicker than ever to make your car mirror-bright. A little brisk rub- bing with Du Pont No.7 Polish, and your car sparkles like new. No. 7 Polish is made by Du Pont, world’s largest maker of modern car finishes. That’s your assurance it’s right for the finish on your car. the part mail- fo ereueh i for fer good DUPONT POLISH When Answering Advertisements Please Mention May Modern Mechanix 117

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This Sidewalk Runabout Biggest Little Show On Earth [Continued from page 75] down on a lathe, as in Fig. 11. This of course requires a pattern. Another very satisfactory wheel used by the writer for several small power vehicles is a 3-inch by 12-inch disk with balloon tire. It is assembled with six small bolts through the hub, and by substituting longer ones for these, a combination brake-drum and drive pulley can be bolted securely to the wheel. A spacing ring will be necessary to hold the drum away from the tire, as illustrated in Fig. 11. The rear wheels turn on a stationary steel axle. This is secured to the wooden cross-member at rear of frame by means of J-bolts, simply a 14-inch carriage bolt with the head cut off and the end bent as shown in Fig. 6. Steering knuckles and a built-up axle are used on the front end, Fig. 9. Construction of these parts requires welding, bending and drilling only, and the wheel spindle must be turned to accommodate the standard wheel bearings. Figs. 4 & 5 show the complete chassis as- sembly. The sills or stringers are 114x2-inch oak, with 2x4-inch oak cross-members where indicated. The chassis is 4 inches wider at back than in front. After the front axle is bolted to the sills, a pipe nipple socket for the bottom end of the steering post is installed. A plywood floor is then carried as far as the back of the seat. Upon this is erected a strap iron frame to support the upper end of the steering post as well as hood. The steering wheel may be either a full size auto wheel, or a hardwood rim screwed to a cut-down Model-T spider. For the hand lever a pipe, bar or section of seamless steel tubing is bent to a right angle and carried in a pair of bearings screwed under the sills, as shown in Fig. 4. An arm is welded onto the lever for attaching the brake cables and a yoke and link connect the lever with the idler pulley assembly. Fender bars protect the rear wheels, and the engine bed is mounted on the rearmost cross- member and one just behind the seat. The brakes consist of brake-lining riveted to a shoe made in the form shown in Fig. 7, which is welded to a sliding bar, carried in a sheet steel guide screwed to the chassis sill. A tension spring holds it away from the brake drum when not applied. A very satisfactory clutch consists of an idler pulley mounted on a sliding bar as in Fig. 8. This tightens the belt on the drive pulley and starts the little car smoothly. As this type of engine is not arranged for variable speed, no controls are necessary, unless a shorting switch, convenient to the hand while driving, is desired. Various makes of engines can be used in this car, the drive arrangement being identical. For only one-half horsepower, have your wheel- pulley at least 9 inches in diameter. This will not give any startling speed, but enough power. 118 [Continued from page 51] Also, while he boasts the longest neck in the world, he is unable to reach the ground without spreading wide his front legs! A page from ancient Rome is next, with two handsome chariots, one of them driven by none other than Ben Hur! Then come colorful figures on horseback, and groups of walking figures—soldiers, clowns, policemen, etc. We quickly discover that the walking figures are mounted on concealed tram- trucks, which gives them the startling lifelike motion. Standing at one end of the arena, watch- ing the horses’ heads bobbing up and down and their wide hips swaying, with the drivers’ reins swinging back and forth, one is fascinated by the impression of reality created. Last in the parade is an object without which no circus would be complete—the old steam cal- liope! Gay in brilliant red, white and gold, it rumbles along, wheezing its spasmodic blasts, while the operator punches away at the piano- forte. When the parade passes from view, we turn to the Main Show. It is a three-ring affair, and one would have to be Argus-eyed to see half the interesting acts performed by the bare-back riders, the galloping ponies, the contortionists, the Japanese acrobatic troups, the tight-wire and trapeze artists—as they flash back and forth “with the greatest of ease.” The entire show is continuous, so we may stroll around the other tents—the Dressing Tent, for the use of the actors; the Horse Tent, with its collapsible water and feed troughs; the Cook Tent and Commissary, with its stacks of tiny canned goods, its miniature bales and sacks of [Continued on page 127] U. S. Needs Planes, Men [Continued from page 46] firing; by dropping thousands of bombs, by air missions peculiarly designed and devised to test by the crucible of stern reality the courage. re- sourcefulness and training of our fighting airmen. One of the greatest steps this nation has taken since the war in military effectiveness was the formation of the General Headquarters Air Force and that organization has fulfilled the ardent hopes of its founders. It is small but it is effec- tive; it is undermanned but it is soundly organ- ized, properly staffed and ably led. In computing the strength of any air force, one can count not only machines in existence, but he must determine how soon other equally effec- tive planes and engines could be produced to make good the recognized high loss rate. What is the state of our aviation industry in this country? It is not as large as that in one or two of the other nations. England, undoubtedly,

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and Germany certainly have more plane and engine production capacity in being than we have in this country. But here again our quality is superior. We are fortunate in having several well established aviation engine factories, capable of rapid expansion. We have a large number of airplane factories manned by capable engineer- ing staffs and trained executive control. These, too, could be enlarged rapidly. Our civil aeronautical manufacturing industry has been responsible for placing this country in the lead in the civil aviation field. This leadership is manifested by the most successful air line operation and by the fact that we export more airplane products than any other foreign nation. Also our air liners are favored equipment on many of the leading foreign air lines. In taking stock of our civil industry and visualizing the rapidity with which it could re- place war time plane losses, we must not lose sight of the fact that airplanes and their engines cannot be turned out over night. Contrary to popular conception in some quarters, it takes five years to develop a new airplane type—five years from original conception to quantity pro- duction. So, obviously, when war comes we shall be compelled to go into production on types already produced in.quantity. Despite this earlier experience on these particular types, it would take more than a year to double the size of our present air force. The length of time it takes to fabricate new planes, plus the fact that air forces are the armed forces first to enter the conflict, make it necessary to have adequate air forces actually in existence on mobilization day. The United States possesses the raw materials needed in airplane construction in greater abun- dance than any other nation. This is an asset which is sometimes overlooked in evaluating our air strength and resources. In visualizing our probable missions, our war plans and our geographical locations, a few fac- tors only may be discussed publicly, for obvious reasons. .Prominent among these is our much vaurted isolation. Paradoxically, the airplane, which is rapidly destroying our geographical iso- lation, must be primarily depended upon to pro- vide us continued isolation—to protect us from air invasion. It is now generally recognized that just as armies guard land frontiers and navies protect our sea frontiers, so our Air Corps alone adequately can defend our air frontier. Whereas it is perfectly true that we have friendly neigh- bors, north and south, and broad oceans east and west, those oceans are rapidly becoming less and less of a barrier to air passage. Then, too, there is no assurance that our sky frontiers may not be menaced by sea based aircraft or by air- planes flown from temporary island bases less distant from our shores. , I agree fully with the Chief of the Air Corps, who recently wrote: [Continued on page 129] When Answering Advertisements Please Mention May Modern Mechanix ‘Use SMOOTH-ON No. 1 for. tightening and anchoring | Try any one of the following jobs and see for yourself how easily and quickly dependable tightness is produced. SMOOTK-ON Loose tool and cutlery handles (1):—Fill hole with Smooth-On and force shank in. Stripped wood screws (2): —Reset in holes filled with Smooth-On. Excellent for loose hinges, locks, hooks, drawer pulls, ete. Loose nuts (3):— Lock by putting Smooth-On between base and seat. Try this on oven handles, etc. Making oversize threads hold (4):— Fill annular space with Smooth-On, Anchoring in tile (5): —Set screws in holes filled with Smooth-On. Anchoring in concrete (6):—-Chip out hole, insert bolt with head in and fill annular space with Smooth-On. Use nut and washer for fastening attached part. Excellent for holding shelf brackets, cabinets, partitions, etc. Smooth-On No. 1 is ideal for tightening parts and stopping leaks because of its low cost, its simplicity of application and its unique properties of hardening into metal and expanding while doing so. No heat, special tools or previous experience are required, and judicious use as per instructions in the Smooth-On Home and Auto Repair booklet assure perfect results. If you take pride in doing home tinkering well and like the big savings of time and money, keep a copy of this booklet and a small can of Smooth-On No. 1 in your work bench. The first of many ‘routine or emergency jobs on which you use Smooth-On No. 1 wili repay its small cost, possibly many times over. HOME ar AUTO REPAIRS Mail coupon for the booklet and get Smooth-On No. 1 in 7-0z. or 1 or WITH — SMOOTH: ae 5-lb. can from your hardware store or if necessary from us direct. Write for SMOOTH-ON MFG. CO., Dept. 69 574 Communipaw Ave., Jersey City, N. J. Please send Smooth-On Home Repair Book, Name Address .. Doit with SMOOTH ON 119

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EVERYTHING || You NEED IN & PHOTOGRAPHY T'S out, Camera Fans—new Spring edition of the catalog that saves you REAL money! Latest type cameras, famous names, everything you need in photography at prices you can't beat anywhere! Don’t buy that camera until you've seen this valuable FREE catalog. Mail the coupon for your copy today. Camera! Action! WHOLESALE RADIO SERVICE ft NEWYORK, N.Y. ẹ CHICAGO, ILL. e ATLANTA, GA. 100 SIXTH AVENUE CAMERA EXCHANGE ORIGINATORS | SINCE 1890 148 pages PRICE 50c

The “Tin Can Special” [Continued from page 106] procedure is used: Lay out the line along which the cut is to be made in pencil. Place a straight- edge along this line and make one firm cut along this line with a glass-cutting tool. If the line is not clean and complete the first time, it is practically useless to go over it. Then place the glass over a sharp table edge, with the cut away from the edge, and press firmly down. This will give a perfectly smooth and straight break. If the negative box is made properly, it will fit snugly behind the camera in such a manner that the camera frame overlaps. Before assem- bling, the inside of the box and the surface cf the wooden camera mounting should be painted dull black in order to minimize internal refiec- tions that may cause later trouble. [Continued on next page]

Filter Facts And Factors [Continued from page 109] scatters green and red light very little, so if the blue light is cut off by means of a yellow filter and the picture taken by the green or combina- tion of green and red light, the haze disappears

| from the picture and the scene appears sharp and clear. Since every filter, regardless of its ccicr or depth of color, removes part of the total white light that normally passes through the lens. it naturally follows that the exposure must ke in- creased to produce satisfactory negatives. The number of times the normal exposure must be multiplied to give the correct exposure with the filter is called the “filter factor.” For instance, if normal exposure with a given film is 1 10 second at f. 16, and the factor of a filter is 2. the exposure must be doubled; this can be dene ty leaving the diaphragm at 16 and setting the shut- [Continued on page 125]

Meter Tests Reading Light [Continued from page 102] metabisulphite for 5 minutes. To make the piece of “tint” paper, lay a scrap of the sensitive paper under a reading lamp. that you know, from pre- vious experience or the advice of an electrician, is of normal brightness; or, use a 60-watt bulk at a distance of 3 feet. It will have darkened to the required shade in 2 minutes; then duplicate the tint with water color for the tint that is used over a part of the meter window. As can be seen from one of the illustrations, the sensitive paper is held against the window with a spring, and turning the lid will bring a fresh section under the window for each test. Reserve discs can be stored in the case.

Accept No Substitutes! Always Insist on the Advertised Brand!

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The “Tin Can Special” | [Continued from page 120] An old tin box serves as a lamp-housing. This is not a stunt; most tin boxes are air-tight and hence light-tight, so that the constructor is saved the trouble of making a light-tight box. Further- more, the inside of the box is usually very brightly plated, which makes the box an ad- mirable reflector. The box can be either round or square, as long as the cover is big enough to include the whole area of the negative box, with some overlap. The box itself should not be smaller than the one de- | scribed here as over-heating would result in a | smaller box. Cut the cover as shown on page 106, and slip the bent sections into the negative box; line up all the joints flush, fasten the lower portion with wood screws as in the photographs, and solder all around where the cover joins the negative box. This makes a firm, light-tight assembly. Next mount a lamp-socket as shown, allowing about one inch clearance from the bot- tom of the tin can. When the can is inserted in its cover, the camera and lamp-housing as- sembly is complete. The construction of these units should be clear from the photograph on page 105 and the sketch on page 106. It is advisable to paint the easel with white enamel, so that the images show up clearly when focusing. A shelf bracket supports the easel, which is further secured by wood- screws in the enlarger baseboard. The guides can be made from lengths of quarter-round or flat molding. In laying them down, the camera base should be used as a spacer, thus insuring a close fit. A coat of var- nish stain completes the job. Remember that the photoflood gets very hot if allowed to burn for any length of time. If the printing time exceeds twenty seconds, it is advisable to break up the exposure into periods of about fifteen seconds, allowing a short time in between for the enlarger to cool down. Gen- erally, however, it will not be necessary to ex- pose longer than twenty seconds. The iris dia- phragm should of course be wide open, and the shutter set for “time.” Enlarging paper is fas- If you are interested in any of the items mentioned in this issue, send a stamped, return envelope for the address of the manufacturer. NOTICE Changes in the make-up and title of this magazine, designed to make your favorite publication better than ever before, will be- come effective with our next issue. Be sure and reserve your copy now. Our new name will be—“MecHaANIx ILLUSTRATED.” When Auswering Advertisements Please Mention May Modern Mechanix MAKE YOUR PICTURES LIVE IN LIFE SIZE AND FULL COLOR WITH AN argus PROJECTOR For owners of Argus, Contax, Leica, Retina, Bantam Spl. and all other 35 mm. Cameras. With an ARGUS projector photography is more fun than ever before. There’s a new thrill wher you see your pictures on the screen in life size and full color. And everyone can now afford to own an ARGUS projector. MODEL CP The outstanding projector value— modern styling in beautiful finish. Has 4” high-pre- cision lens; com- plete with 100 w. lamp and carrier. $1500 MODEL B Powerful projector of improved design with swivel head and tilting lever. Automatic film pressure release preventsscratching Alm. Complete line of accessories avail. able. $3250 ARGUSLIDE KIT 75¢ Contains glass, patented binding stickers and film centering masks for making one dozen complete slides. ARGUSLIDE BINDER KIT Has complete materials for making 6 dozen slides p/us the ARGUSLIDE binder for assembling and sealing slide glasses. $ 5.00 INTERNATIONAL RESEARCH CORPORATION 186 FOURTH AVENUE ANN ARBOR, MICH. T24

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Rutland Parch- ing Plaster makes a perfect patch as lasting as the wall itself —and anyone can use it. dace cwith=squabe Marketed when only 25 days old. Write a post- card, get FREE EYE-OPENING Picture Book. Melrose, Mass. Why breed for ordinary trade when these great luxury national markets are wide open for all the SQUABS you can ship, every day in the year? Go after this desirable, profitable trade now, Write today to RICE FARM, 602 H St., 3-IN-ONE OIL KEEPS GOOD For cleaning and oiling tools, for adding smoothness and speed to action points of braces, always use 3-In-One Oil. Its ““triple-action”’ cleans, oils, prevents rust. At hardware, drug, groceryand10¢ stores. 3-IN-ONE OIL 122 Test Your Model Airplanes [Continued from page 77] ailerons, rudder and stabilizer of the model. The cabinet of the wind tunnel can be made from scrap lumber and the outer sheeting can be constructed from wallboard. A celluloid win- dow should be incorporated in the cabinet’s con- struction so that observations of the model’s movements can be made. The overall dimensions of the cabinet can be increased if desired. The honey-comb core can be made from strips of sheet metal, notched half through and inter- locked, as shown in the sketch. The notching of the strips can be done quickly by clamping all the strips together and then sawing half through with a hack-saw at one-inch intervals. The air pass, which directs the air blast from the fan to the cabinet, is made from scrap sheet metal, following the dimensions shown in the sketch. This should be nailed or screwed directly to the cabinet framing. Be sure the air pass is fitted with an end block featuring a diameter capable of accommodating the whirling blades of the fan. The dynamometer assembly is clearly shown in the sketches and, when completed, is screwed to the floor of the cabinet by means of a wooden bracket mounting. The model to be tested is suspended in the rubber-band yoke of the dynamometer and braced with other strands of rubber, which extend from the nose, wing and tail. These strands are solely to balance the model in the air stream and should therefore have very little tension. The lift indicator scale of the dynamometer should be calibrated to read in the same units as the postal scale which is used to register the drag of the model. This can be accomplished by ad- justing the tension spring of the dynamometer. The movable lead weights on the balance arms of the dynamometer should be adjusted (to com- pensate for the model’s weight) so that both the lift and drag scales register zero BEFORE the fan is started. Once the fan has been turned on, the lift and drag will be indicated immediately. Construct A Gate Leg Table [Continued from page 83] Top Batten and Bottom Rail: 2 pieces, 1” x 3” x 13” Square to exact sixes. Mark cutouts for gates at position indicated in plan. Mark and bore end of each piece for dowel joints and scribe co- inciding lines on end cleats and feet to assure accuracy of dowel joints in later assembly. Shape edges of these members as indicated in plan. Mark off and bore holes for pivot dowels. Bore pilot holes in top batten for screws which will later attach under structure to top. Glue and clamp dowel joints, assembling ends, top batten and bottom rail. Accept No Substitutes! Always Insist on the Advertised Brand!

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Gate Rails—(Top and Bottom): 4 pieces, 1” x 144” x 9” Square to sizes and cut tenons. Assemble to gate post and pivot post. Bore ends of turned pivot post for pivot dowels. Attach gates to part already assembled, tapping pivot dowels into place through top batten and bottom rail. Glue pivot dowels into place. Top: 2 pieces, 56” x 942” x 20” (leaves) 1 piece,54” x 5” x 20” (center piece) Square pieces to size and mark to oval shaping according to graphed template shown on plan. Shape edges to regular half rounding. Set hinges into place. Glue gate stops on under surfaces of leaves at position indicated in plan. Assemble top to under construction with four 14%” screws run- ning through top batten. If the table is made of walnut it should be thoroughly sanded before any finishing materials are applied. Too much emphasis cannot be placed upon this point, for walnut is a wood which re- quires a maximum of sanding in order that its best characteristics of graining and texture may be brought out. The craftsman should be most cautious in his selection of stain. A good quality oil stain is highly suitable but if the individual desires to mix his own he should experiment on scrap pieces of walnut before applying this stain to the article itself. In this way he may determine the exact tone desired. It is considered good practice to stain the entire article first before applying the filler. The pri- mary coat of stain is thoroughly and evenly rubbed, after which a filling solution, colored with the same walnut stain, is rubbed into the graining of the wood. Filler must be carefully re- moved before the final coat of stain is applied. While it is sometimes contended that a second coat of stain is unnecessary, still, the craftsman will find that such practice is expedient for the sake of obtaining absolute uniformity of tone. When the stain has become thoroughly dry, apply a thin coat of white shellac. This is per- mitted to dry and is then lightly rubbed with fine steel wool. Two additional coats of thin shellac are then applied, each in turn being rubbed with steel wool. The entire table is then carefully waxed and rubbed to a warm luster with a soft cloth. NOTICE Changes in the make-up and title of this magazine, designed to make your favorite publication better than ever before, will be- come effective with our next issue. Be sure and reserve your copy now. Our new name will be—“MECHANIX ILLUSTRATED.” Treet Topics YOU'LL LOOK a LIKE THIS ~ AND THEY'LL LOOK LIKE THIS ~yGon> SO CLEAN- LOOKING / ~AND YOUR ~ BANKROLL WILL SS LOOK LIKE THIS ~ IF YOU TREET YESSIR Do THIS: i. sanik -AND TREET YOURSELF A) TO A PACK OF PERFECT SHAVES’ Single- ` Edge FOR GEM AND EVER- READY RAZORS Treet Safety Razor Corporation, Newark, New Jersey When Answering Advertisements Please Mention May Modern Mechanis 123

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FREE TRIAL OFFER NEW REMINGTON NOISELESS PORTABLE AS LOW AS 10%. AMOUS Remington Noiseless Portable that speaks in a whisper, as little as 10c a day. Standard Keyboard. Automatic rib- bon reverse. Variable line spacer and all the conveniences of the finest portable ever built. PLUS the NOISELESS feature. Act now. Send coupon TODAY for details. You don’t RISK a Penny. We send you a Remington Noiseless Portable for 10 days’ free trial. If not satisfied send it back. We pay all shipping charges. Typing course and carrying case. You will receive FREE a complete simplified home course in Touch Typ- ing. Also, a handsome, sturdy carrying case. No obliga- tion. Mail coupon for full details —NO Remington Rand Inc., Dept. 141-5 465 Washington St., Buffalo N. Y. Tell me, without obligation, how to get a Free Trial of a new Remington Noiseless Portable, including Carrying Case and Free Typing Course for as little as 10c a day. Send Catalogue. 60 POWER TELESCOPE $2.19 VARIABLE EYEPIECE. 20X—40X—60X NEW! Three telescopes in one. 3 different mag- s nifleations. 20 power for ultra-bright images with 40 and 60 power P for extra long vange. Guaranteed to bring distan objects, people, sports events, empa: moon, etara, etc. thmes as close, for anywhere the money, Closes to lesg than a foot i in length. Multiple a etem, 30 mm, objective, in heavy brase mount. Directions included for uaing as a compenn 4 lens microscope. American made. We pay the postage. Only $2.19, Catalog of Microscopes, Binoculars, etc. FREE on request. BROWNSCOPE CO., ‘Dept. 75, 5 W. 27th St., New York, N. Y. INVENTORS PATENT YOUR IDEAS SEND FOR FREE BOOK ==> HOW TO OBTAIN A PATENT Written by a Former Member of the Examin- ing Corps (1922-24) of the U. S. Patent Office, If you want to profit by your idea, you should 7 take steps io apply for a Patent at d once. Your first step is to get this Free Bock. This interesting illustrated book contains valuable information you should have, It tells you fully hcw to obtain a patent on your idea in the quickest way. With this Free Book you will aliso receive a “Record of Inventicn’’ ferm cn which you can easily record your Idea. Personal and Cenfidential Service: Your case wil) be personally handled only by a Registered Patent Attorney who is also a Former Member of the Examining Corps of the U. S. Patent Office. All come munications confidentlal. MAIL COUPON TODAY for FREE PATENT BOOK and RECORD OF INVENTION Form CARL MILLER REGISTERED PATENT ATTORNEY FORMER MEMBER EXAMINING CORPS U. S. PATENT OFFICE [] K oolworth h Bldg. 35th Floor, Dept. 58B, New York City P p MIL ING, Dept. 588, WASHINGTO B mie eee me your Free Book, “How to Obtain a Patent,” ‘and B H your ‘Record of invention’! form i | H NAND ere Era P E z E I e ADDRESS ....... jjaran PAREEN RETRE NELERE ANANS i 1 | hittnaD han enna wenn nen wee mee A Home-Made Drag-Saw [Continued from page 87] a model-T Ford engine connecting rod, as indi- cated in the layout. A universal joint, which is placed between the engine drive shaft and the automobile steering gear worm that serves as a reduction gear assem- bly for the crank-arm shaft, consists simply of a piece of extra heavy duty, high pressure air hose. The reduction gear, as stated before, consists of a heavy worm steering gear from an automobile and is geared to the crank-arm shaft that moti- vates the saw guide by means of two timing gears taken from a model-T Ford. The crank-arm shaft is made from a 1929 Whip- pet auto axle, turned on a lathe to fit the bearings at hand so as to form a pressed fit with the gear, utilizing the key-way and threaded end to secure the gear, cam and crank-arm to the shaft. The reduction gear and crank-arm shaft are assembled on pillow-block bearings and bolted to a 36-inch steel plate which, in turn, is bolted to the frame. The cam that rocks the saw is made of one-inch soft steel which is turned to a three-inch diameter and bored off center. The cam bearing is made of two pieces of 1x2%4x5-inch soft steel bored to three and one-quarter inches and babbitted to fit the cam. This is held in place by two three and one-half-inch collars, one-eighth-inch thick, as shown in assembly sketch. The cross-head guides are two model-T Ford steering rods, the cross-head itself being a piece of steel 15x6x12 inches in size with two 1x12- inch pipe nipples bolted and welded to it. The nipples are babbitted to fit the guide rods. The crank-arm is steel, 12x2x12 inches in size and has a nine-inch throw. The saw should have an eighteen-inch stroke, the connecting rod between the cross-head and the crank-arm being made up from one-half-inch pipe with babbitted tees at each end. Guide rods for the saw are secured on one end by the cam bearing and on the other end by a 14x2-inch piece of strap metal bent to form an anchorage for the saw handle. A Model Airplane Jig Saw [Continued from page 81] is bolted to the commutator. The lower grip should center about one-half inch from the com- mutator, The arm is a 34 inch steel rod, bent as shown, flattened at one end, and drilled to take the upper bearing. The block forming the rear of the frame is drilled to take the rod, which is fastened in place with two 3/16 inch screws. The in- terval between the arm and lower blade grip must be determined by the length of the upper bearing and the size blades to be used, 124 Accept No Substitutes! Always Insist on the Advertised Brand!

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Filter Facts And Factors [Continued from page 120] ter to 4% second, or leaving the shutter at 1/10 second and opening the diaphragm to 11. Accompanying all roll and cut film is a sheet of instructions which includes filter factors for each particular kind of film for daylight and mazda illumination and for particular filters made or sold by the manufacturer of the film. If filters of another make are used, the given filter factors may or may not be correct, and it is highly advisable to try several exposures of the same scene with slightly different factors. This is especially necessary if the normal ex- posure is made by guess work, without the aid of a reliable photo-electric type exposure meter. If the “normal” exposure is off a little, the nega- tives with the filter may be over- or underex- posed very badly. While the exposure latitude of most film is sufficient to cover reasonable variations from the ideal exposure, it may not be enough to take care of an incorrect exposure whose error is multiplied from 2 to 5 times by the filter factor. Filters for amateur purposes consist of a thin sheet of dyed gelatin cemented between two pieces of glass, and mounted in a metallic ring of some sort that slips over the camera lens. Actual colored glass (that is, glass to which a coloring pigment is added during the firing process) is used for some type of expensive filters. It should be evident to any sensible person that a filter must be of the same high optical quality as the camera lens itself if the sharpness, detail and other characteristics of the picture are to be retained, but many owners of expensive minia- tures costing several hundred dollars skimp on their filters, thinking of them only as “acces- sories,” Gelatin filters are susceptible to heat, and must therefore be protected in a box or container of some kind if carried on the person. They should be handled only by their edges, and wiped clean of finger marks with lens tissue before they are used. The best way to attach them to the camera is by means of a combination sun shade and filter holder, an inexpensive accessory of great value.

A list of addresses of manufacturers of items mapa in MODERN MECHANIX will be sent to any reader upon receipt of a stamped, return envelope. NOTICE Changes in the make-up and title of this magazine, designed to make your favorite publication better than ever before, will be- come effective with our next issue. Be sure and reserve your copy now. Our new name will be—“MECHANIX ILLUSTRATED.” When Answering Advertisements Please Mention

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‘More PEOPLE MORE FUN in this sturdy boat { A 5] è Orp Town Boats take a tremendous Joad for their size. They’re trim craft, with graceful lines for speed and com- fort. Built and braced to stand the heaviest outboard motors. You never have to baby an Old Town. There are tough, fast, open- deck models for sport. Big seaworthy boats for the family. Made of the finest materials by expert craftsmen. ; FREE CATALOG He boats for sport, all-wood boats for the family, and all kinds of Canoes, Out« board Boats, rowboats, dinghies. Write to- day.. Address Old Town Canoe Company, 465 Main Street, Old Town, Maine. ` A 3 A — “Old Town Boat WIND DRIVEN Electric PLANT Build Your Own—We Show You How! Make auto generator light buildings, play radio, run washing machine and other motors from FREE WIND POWER. Earn money making for others. Dime brings complete building plans and 1938 catalogue listing over 500 windeharger electrical items, Most complete wind- charger eatalag; welders, electric fence, ete., over 1^0 other generator changes into 6-12-32 and 110 volt plants, LEJAY MFG. CO., 414 Lelay Building, Minneapolis, Minn. _A Wrought Iron Globe Light [Continued from page 71] the size of the base and the band will have to be varied accordingly. If a 7-inch globe is used, it will be necessary to have approximately 6 feet of band iron %-inch by %-inch. The iron is hammered on one side with a ball- peen hammer to relieve the stiff and cold appear- ance, A little practice on a serap piece of iron will develop the desired technique. Carefully straighten out the iron before proceeding with the bending of the pieces. In bending the band and the scrolls it is well to check the work against full-size drawings laid out on paper. In order to insure the making of uniform scrolls, use a scroll former as shown in the sketch. To make a former use a piece of iron approximately 14-inch thick. Drill a 3/16- inch hole and then complete the design with a hacksaw and files. The scrolls may be easily bent if the iron is first heated red hot, If a forge is available, weld the band, otherwise splice the ends. The central rivet holds the splice as well as the cross piece of the base. The holes accommodating the rivets are countersunk so that the rivets may be hammered flat with the surface of the iron. A ¥%-inch pipe nipple one- inch long is used to attach the lamp socket to the band. The electrical cord should be of the flat rubber covered variety and is attached to the under side of the iron band with small cotter pins or wire hair pins passed through the small holes and clinched on the outside. Protect the iron from rust by the application of thin coat of clear lacquer or a coat of black paint. If black paint is used, rub out high lights on the iron with a cloth while the paint is still wet. Earn Spare-Time Money | THIS NEW PLEASANT WAY/ Learn how you ean build up a profitable spare or full-time business in your own home, This new booke “How ta Make Money in Woodworking” is crammed with practical tested ideas, plans, and suggestions, Tells you exactly what to mate, how to make it and how to sell it. Describes plans that have worked for others, Woodworking, the new way, is light, Pleasant, and profitable. Send only 25e and complete book will be malled postpaid, Sallsfaction guaran- teed or money refunded. Write to Dept. 31538, 6 R Delta Mfg Co. Sock e LENNA AVE. 126 Cigarette Box Has Trick Lid [Continued from page 91] the corners, as shown, then drill small holes for the pins at right angles to the notches. Do the same with the lid. The holes should be just large enough to receive small brass escutcheon pins. Form a loop at one end of each of the four pieces of brass wire, then drill each loop to assure a perfectly round hole so that the hinges will work smoothly. The loop ends attach to the lid. Form the other ends so that each turns back on itself to make a U, for attaching to the escutcheon pins in the box. Loops cannot be used here as allowance must be made for a shortening of the wires when the lid is raised. Red enamel is an attractive finish for the box; cover the bottom with black felt and attach an imitation-cigarette handle to the lid. The im- itation cigarette is made by coating a 234-inch dowel with white enamel and pasting a brown paper band to one end to simulate a cork tip. Glue snippings of red foil to the other end to imitate fire. Accept No Substitutes! Always Insist on the Advertised Brand!

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Biggest Little Show On Earth [Continued from page 118] flour and meal. There is the Power Wagon on which is mounted the gasoline engine and dynamo, which (supposedly) furnishes power for the show; the Property Wagon, Tanker, Pole Wagon, Stake Driver and all the others. We may watch the Stake Driver at work as it drives the long tent pegs into the ground. It is with extreme reluctance that we take leave of Parke’s Biggest Little Show On Earth. And the children—well, try to drag them away! We'll not be content to depart, however, without asking at least one of the thousand and one ques- tions that visitors always ask. We quickly dis- cover that Circus-whittler Clyde Parke is not only a genius, but a genuine host. There is only one question he cannot answer: “How much is the circus worth?” “Well,” he laughs, “I wouldn’t take a dime less than $30,000 for it!” Now the question arises, “Why a miniature circus?” Asked “why” a dozen years ago, Mr. Parke would have been stymied for an answer. He did not set out to be a wood carver. Nor did he intend being a circus operator. By profession he is an accountant. He just “happened” to dis- cover his ability with a knife. The carving of miniature wood figures gradually developed into the circus idea. Like all small boys—and most oldsters—Mr. Parke was an ardent circus fan and never missed any of the big shows that came to town. Being a close observer, he saw many things the crowds missed. These youthful observations are evident today in his great show. Nothing is missing. Every detail almost “breathes” naturalness. The only tools used in his work were a small puzzle-making machine, consisting of lathe, sander, jig-saw and his pen knife. His method of carving a figure is simple: First, he outlines it on the face of a block of Michigan pine, the wood used by pattern makers. Then the large portions are sawed out. The balance of the work is done with carving knife and gouge. It takes about 12 hours to whittle out a horse, with harness on; about eight hours without harness. Other figures require propor- tionate periods of time. Shellac, or a bath in lacquer, after the colors have been applied, finishes the figure. Animation of the animals and actors in their astounding feats is accomplished by a single quarter-horse power electric motor, remotely controlled. Today, at 50, Clyde W. Parke is master of the most unique circus in existence, one which old- time showmen acclaim as the most complete and amazing mechanical marvel in the world. In a five weeks’ run staged in Memphis some months ago, attendance ran into the thousands, proving that miniature shows have plenty of “box office” appeal. When Answering Advertisements Please Mention May Modern Mechanix —with all types INTERNAL COMBUSTION ENGINES, ELECTRIC POWER GENERATION, Etc. YOU MEN who are sincerely ambitious to make good in the Diesel and related industries, want to know the true facts—you want to know about employment opportunities and employment requirements. For 33 years, National Schools, a recognized leader in the field of trade education, has played a vital part in helping wide-awake men to qualify for success in industry, National Schvols—a million-dollar trade school—will supply you with a sincere, honest statement cf facis on what you should do to get into the profitable Diesel Industry, No exaggeratlons—no mis-statements, YOU NEED REAL SHOP EXPERIENCE WITH TIME-TESTED TRAINING. Mail the coupon below, In the literature you will be sent, you will see exactly how other men like you are preparing themselves for success in National's modern training shops. You learn on the latest, finest equipment. You do real job work. You learn by time-tested, shop-practice methods. Your training is fascinating in every detail. You are taught how to make good, and helped to make good after you graduate, All of this and much more is clearly pictured for you in the Free Book of Facts we will send to you, TRANSPORTATION ALLOWED TO LOS ANGELES Natlonal Sludents are allowed coach railroad fare from any point in U. 8. (Canadian students from nearest point of entry). Student social life includes inspection trips, excursions, athlctic activities, ete. Special doctor service. Personality coaching. Many students are helped with spare-time jobs to earn room and board while learning. (Canadians excepted.) Graduate employment cooperation, NAL SCHOOLS THA Zo BOOK Angeles g Tree Look > NATIONAL SCHOOLS (established 1905) Dept. MMA-5 3 ¢ 4000 South Figueroa Street, Les Angeles ; (i Please tend me, without ebligation, your FREE BOOK and informotion Ç regarding Diesel Employment Opportunilies and Requirements. $ NAME AGE (g ADDRESS — ~ CITY STATE. PPDDA PD AD PD PALDADPDPDPPDPDA PAPAS 127

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lof the radio catalog supreme! Act}: [now to get first-hand information], jon all latest type radio equipment. f {Read about new Lafayette super ireceivers for ’38—advanced line o iLafayette Public Address — real]. “buys” in famous name cameras {Prices you can’t beat anywhere. Get ithis amazing FREE catalog NOW! WHOLESALE RADIO SERVIC fn NEW YORK, N.Y. e CHICAGO, ILL. e ATLANTA, GA. 100 SIXTH AVENUE 901 W. JACKSON BLVD. 265 PEACHTREE STREET BOSTON, MASS. e BRONX, N.Y. @ NEWARK,N. J. @ JAMAICA. L.I- WHOLESALE RADIO SERVICE CO., INC. H Smt W. Jackson Blvd., Chicago e 100 Sixth Ave., Now York RUSH (Mail to nearest Warehouse) Mis COV g Rush Catalog No. 71-2268 C Send part list== wow FOR Name odd ono thine aoa nE oane chance to buy the New Improved 7? kit for $5.00 or the assembled motor for $10.00. Send S1. Shipped Exp. Coll. for balance same day. Catalog 3c. Dealers write. S, 854A East 149 St., New York SHUNNED AT SCHOOL BECAUSE OF PIMPLES? Take steps to free your blood of skin-defiling poisons : GHQ MOTOR Stop being the victim of ugly hickies. Don't be shunned and laughed at. Get right to the root of the trouble. It may be poisons in your blood. Between the ages of 13 and 25, important glands are developing. These gland changes often upset your system. At the same time, waste poisons from the intestinal tract may collect in the blood stream... bubble out on your skin in disfiguring pimples. You want to rid your blood of these skin-irritating poisons. Thousands have succeeded—just by eating Fleischmann’s Yeast, 3 cakes a day. The millions of tiny, living plants in each cake help you keep these poisons out of your blood, give you clearer, smoother skin. Many get splendid results in 30 days or less. Don’t waste time and run the risk of permanently damaged skin. Start eating Fleischmann’s Yeast today! A Utility Table For The Auto [Continued from page 98] the compartment and to be lowered to its normal position without interference with the hinges. In order to do this, slots must be cut into the back of the table. These slots must be large enough to clear the hinges at all times. The post that carries the weight of the front part of the table is a piece of 114” square stock cut just long enough to reach from the under side of the plywood top to the floor of the car when the table is held in a level position. Square across this post at one end is nailed a triangularly shaped brace about 10” by 6”. The 10” side is placed square with the end of the post and the 6” dimension runs down along the post as shown in the diagrams. The two sides of the triangle, where the knees might come in contact with them, can be concaved somewhat to allow more leg room if desired. [Continued on page 142] To Reduce Hum In Receivers [Continued from page 100] tube and trace the wire to a grid leak or volume control, Connect the resistance-capacitance filter between the leak and C-, as shown. Only a few sets used grid filters because of cost considera- tions; however, for about 50 cents per tube, the hum can be reduced to a very low level. Of course, try one tube at a time, as only one tube may be causing the hum. Experience shows that the first a-f tube is the most critical. Earth Bulge Causes Quakes The enormous bulge in the earth that has its crest in the Himalaya mountains is responsible for the terrific earthquakes that sometimes rock interior Asia, Prof. D. Mushketov of the Lenin- grad Mining Institute states, after extensive ex- peditions in which thousands of observations were taken. The deep-seated forces pushed up the crust of the earth in this region as a man in bed pushes up the covers with his knees. Like the covers pulled over the knees, the thick blankets of rock are under tension. They give way from time to time, and that starts the earth- quakes. Accurate measurements made by Pro- fessor Mushketov show that in the Pamir region the curvature of the earth is much in excess of the average curvature of the earth as a whole. NOTICE Changes in the make-up and title of this magazine, designed to make your favorite publication better than ever before, will be- come effective with our next issue. Be sure and reserve your copy now. Our new name will be—“MECHANIX ILLUSTRATED,” 128 Accept No Substitutes! Always Insist on the Advertised Brand!

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U. S. Needs Planes, Men [Continued from page 119] “Two great air doctrines will motivate all mil- itary air work for 1938. The first of these is a realization that airplanes alone do not make an Air Force. Along with modern up-to-date planes must go skilled operating and combat crews, trained maintenance crews, efficient accessory equipment, and ample air bases.” It is my hope that by June, 1940 we shall have the 2320 airplanes needed in our Army Air Corps, and what is equally important, we shall have the trained crews to operate them and make them effective fighting units, plus the trained main- tenance crews to keep them fit and sound. Short- ly thereafter, I hope we shall have supplied that last requisite element, adequate air bases from which to operate our fighting air forces effectively. When those things are accomplished, when that day comes, we shall take our place, heads up, yielding to no nation in defensive strength, proudly proclaiming the safest air frontiers in the world. Sun Spots’ Effect On Earth- Bound Man Told In Book ID you know that the best vintage wines are from crops that grow in those years when sunspots are at a maximum? And that trees show their greatest growth in periods when the surface of the sun shows the greatest number of spots? Or that the Dow-Jones stock market averages follow a curve which is very similar to curves based on sunspot numbers? These are only a few of the many remarkable, but unexplained, coincidences between the activities of plant and animal life on earth and the appearance of those gigantic electro-magnetic disturbances on the sun which man calls sunspots. More and more scientists, and others. are prob- ing sunspots and seeking to learn the relation- ship between their appearance and the multi- tudinous activities of earth-bound man. In his newest book, “Sunspots and Their Effects from the Human Point of View,” Dr. Harlan True Stetson, astronomer and research associate of the Massachusetts Institute of Technology, sum- marizes the knowledge which science now has in its possession to analyze for the truth or false- ness of speculation on this intriguing matter. Dr. Stetson goes out on no limb to forecast, in so many words, a definite relationship. Rather he piles up, item by item, an imposing array of facts which offer a true challenge to those who are skeptical of the sunspots bearing on ter- restrial activity. Sunspots and their effect on i CLEAN OUT ANTI-FREEZE Rust and scale have accumulated in your radiator all winter. They are choking the delicate veins that circulate water and keep your motor cool. An overheated motor is a lazy motor. And overheating may cause costly damage. Clean out your radiator. It costs only 10c. (25c for the largest trucks and tractors.) You can do it yourself in a few minutes. Pour a little Sant-FLusu in the cooling sys- tem. Run the engine. (Follow directions on the can.) Then drain, flush and refill with clean water. Do this regularly, twice a year. Keep the radiator clean and clear. Motors run cooler. Save power. Save repairs. SANT- FLusH can’t harm motor or fittings. You'll find Sant-FLusH in most bathrooms for cleaning toilets. Sold by grocery, drug, hard- ware, and five-and-ten-cent stores. 25¢ and 10c sizes. The Hygienic Products Company, Canton, Ohio. Sani-Flush 4 KEEPS RADIATORS CLEAN “Mga! \ YOU WANT THE BEST FOR’ AN YOUR MIDGET CAR Equip lt with our guaranteed qual- WHEE, ity DISC Your choice of these famous makes 1 y 4 HEELS mounting Balloon Tires. $ At lowest prices. We provide Scooter Kits, Midget auto kis etc. & at great savings. Now is the time to build yours. We also carry a ie of larger Tires and Wheels, Motors, etc. Write for prices. E BILD-UR-OWN DEVICES 5237 Lake St., Dept. B-5, Chicago, EU. human behavior, growing things, business, radio, sunlight, power, earth magnetism and even carrier pigeon flight are presented for the reader to note and draw his own conclusions. When Answering Advertisements Please Mention May Modern Mechanix 129

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BIG MONEY Assembling New l PORTABLE —see how easily thi ster carries his M D KI- have with one—A: SELF at home in a few hours from our num- bered, cut-to-fit Construction Kit—and SAVE HALF the fac- wi tory-built cost, or sell it for big profit! Tell DAD about this educational money- making project! Sold direct from factor; tory prices. Rush 10¢ NOW for Circular 57 beautiful photos of Mead Ki-Yaks. dling, and with motor—Low Factory-to-You Intro- ductory Prices, SG GIft Paddle Offer. J MEAD GLIDERS, 15 S. Market, Dept. M-58, Chicago. NYA T-N Ge] || Wants More zeA LINCOLN TRAINED MEN Prepare now at thls Government Approved Lincoln School for a Good-Pay position in Aviation. Airlines adding millions of miles to flight schedules need more skilled pilots and airplane maintenance men. | with your CK-Ki- Yakf you hurry Factories flooded with orders for new alrplanes need more well trained mechanics, Be a Pilot, Flect of 14 Training Planes. Veteran Flight Instructors prepare you for any Pilots Rating up to and including Transport. Be an Aviation Mechanic. Learn Airplane engine malntenance, overhaul, and repair. Airplane construction: Sheet Metal, Welding. Training prepares you for your Government Mechanic's License. Train now at Lincoln. He ready in a few months for a Good-Pay position in Aviation. Employment Service glven on Graduation. Wrile Today for complete information. LINCOLN AIRPLANE & FLYING SCHOOL 505 Alrcraft Bldg., Lincoln, Nebraska l Pursuing The Postmark [Continued from page 70] abroad” markings, for instance, chronicle the permeation of one nation into another nation for the establishment of what we refer to as “Zones of Influence.” Other postmarks reveal other his- tory. The first-day cover definitely indicates the first day of use of a new postage stamp through its dated cancellation mark. Sometimes, in addi- tion, you will find the helpful inscription, of “First Day Of Issue” in the obliteration lines. At least insofar as U. S. issues are concerned. Among the more popular postmarks are those which bear slogans, or advertising inscriptions. Postmarks are not available to commercial ad- vertisers, but the governments of many nations utilize the postmark to broadcast their services. An example to point is Switzerland, which (as with several other countries) operates and owns its own telephone system. Therefore, the Swiss government will advertise through postmarks, “Telephone Saves Time and Money,” or some similar inscription. The Irish Free State, in broadcasting messages to its people, has also used the postmark. Cne of these sloganized post- marks reads, “Grow More Wheat,” as illustrated. There are also postmarks of an historical nature which advertise fairs and expositions and such undertakings. Quite a number of such items are in existence. All of these postmarks, no matter what group, are always more worthy when on full envelopes (covers), rather than cut from the envelopes. Wherever possible, such covers should be saved in their entirety. At any rate, the pursuit of the postmark is pleasing. The more different types and groups one obtains, the more enthusiastic one becomes. Domestice and foreign are available, and each collector may select one group or generalise. Sometimes a postmark cannot be discovered upon full cover; or it is too expensive for the average enthusiast. Probably it may be had off cover, as a “cut square.” These should be saved, but if a postmark is available, somewhere, upon full cover, it is worthwhile striving to obtain it. Such an item not only shows, conclusively, that postal duty has been faithfully performed; it also shows where the postal duty has been performed. Hints For The Fisherman [Continued from page 90] creation. Several are illustrated herewith which will be found very effective and cost practically nothing to make. Figure 3 shows a minnow made of kacon rind. The “minnow” can he cut to any size from 3 to 12 inches, depending upon the size and kind of fish one is after. Muscallonge, great northern pike, and large mouth bass will take a bait half their own size. The lure can be used with or without a spoon. In some waters where baby-catfish, mudpike, and eels are the chief prey of the game fish, it is well to darken the fatty side of the bacon rind by dipping the rind in a strong solution of potassium permanganate. It will then take on a_ purplish iridescent hue which is particularly attractive. The drawing shows the details of the hook rig-up. This lure can be used either for trolling or for casting. 130 Accept No Substitutes! Always Insist on the Advertised Brand!

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This plate also illustrates a lure which is very effective for bass and for wall-eyed pike in rivers of the Atlantic water- shed. “Lamper” eels come up most of these rivers to spawn, and the baby eels are the prey of all the other fish. Eels for live bait fishing are very difficult to get. They bed themselves in the black sand of the river bank and are as quick as proverbial “greased lightning.” But an “eel” made of bacon rind dyed with permanganate will fool the wisest wall-eyed pike. If used for trolling, it is well to use a small spoon on the head of the ‘‘eel.” There is also shown a “wet” fly which is a very effective “killer” for trout when the water is slightly discolored. This is especially effective in streams tribytary to the Missouri River. When the water is discolored or high, the trout are on the lookout for little ringed worms commonly caller “rock worms.” A black hackle can easily be remodclel to give a fair representation of these worms, The drawing explains the process. Celluloid cement will secure the woollen yarn to the shank of the hook which should be a No. 8 or 10. A simple tool which every fisherman should carry consists mercly of gluing a strip of fine emery cloth to both sides of an old nail file. A keener point can be put on a hook with this tool than with a file. A sharp point is essential for fly casting, because the hook cannot be “set?” into the fish with a hard jerk. Varnish-rubber’s felt serves conveniently for applying line dressing. A piece about % by 1 by 1% inches is split half through and the opening is impregnated with the dressing. Cold cream—the greasy kind—makes a good dressing for soft enameled lines. It will make the line float for the “dry” fly fisherman, and leaves no iridescent, oily film on the water. Every fly fisherman should carry a small piece of chamois with him. It serves better than anything else for dry-wiping a line. Before using, the chamois should be soaked in water and then be wrung out dry. Flies, black gnats and pesky mosquitoes often detract from full enjoyment of a fishing trip. There are nasty, irritating dopes on the market which will keep them away. But using these dopes is like hanging a man to cure a sore throat. A simple means of eliminating the insect nuisance is to cnl a discarded enamel line into 6- to 8-inch lengths and hang the pieces around the brim of the fishing hat. The natural movement of the head will keep the flies ‘‘shooed’’ away. Soft, undressed line will not prove satisfactory, as the strands will become tangled. Enamel line will not tangle. When a creel becomes aged it takes a dark brown color which absorbs the heat rays of the sun. Sensitive brook trout may spoil in a few hour’s time in the hot interior. Every fisherman should carry a small towel so that the fish slime on his hands is not carried to the cork grip of the rod. Jf this towel is white and is kept damp. by draping it over the creel, the fish can be kept cool and fresh. In hot weather, reasonable care must be exercised if one is to arrive home with a fresh and attractive catch. The best means of preserving trout is to clean them immediately upon catching. Then wipe them dry as possible with a towel from which all water has been wrung out. Wrap each fish individually in a piece of waxed paper and twist up the ends. It is well, too, to place a little green grass or wrinkled waxed paper in the inside of the fish to keep the sides apart. Upon returning to camp, each wrapped fish can be held momentarily over a flame to melt the wax. When the wax rehardens, the fish is in a practically air-proof container. They can be carried home and are sure to be in good con- dition when the cook is ready to fry them. A final word! Make your fishing truly a sport. Don’t judge your good time by the number of fish caught. Keep track of your “batting average.” Ten “strikes” and seven fish in the creel is more commendable than sixty “strikes” and thirty fish in the creel. Don't go out after fish. Go fishing.

Psychologist Uses Radio To Check Hams’ Personalities CAN you judge a man’s personality from heating his voice over the radio? The possibility is being tested by a psychologist who is also a “ham” with his own radio trans- mitter in his study, Dr. E. Lowell Kelly, of Connecticut State College. Fifty other amateur radio fans will take part in the experi- ment. Each of them will be rated on 36 different personality traits by personal acquaintances and also by those who know him only by radio. Comparison of the two ratings will reveal to what extent a man’s personality “gets across” through the medium of the microphone. Intelligence, sociability, ‘popularity, initiative, courtesy, cooperativeness, culture, honesty and disposition; these are among the traits to be evaluated on Dr, Kelly’s 36-point scale. If the experiment demonstrates that radio does reveal the personality, another experiment will be undertaken with those amateurs who use only code. When Answering Advertisements Please Mention May Modern Mechanix

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FREE 164 PAGE SPRING CATALOG C EVERYTHING AT LOWEST PRICES Write today for ALLIED’s big Spring Catalog—just off the press! spree event 184 pages packed with everything NEW in Radio. 56 sensational new “KNIGHT” Radios, including Push-Button Tuning models at new low prices; latest Auto Itadlos; Phono-Radio Combina- tions; 6 volt-110 volt Farm Radios; sets for AC-DC, 6 volt, 2 polt and 32 volt operation at unequalled low prices . . . Set- Builders’ Kits of all types from 1 to 14 tubes , .. Amateur Gear in all leading lines . . , Amazing new Sound Systems for every purpose, from 10 to 70 walts ., . Test Equipment for all servicing needs, And more than 12,000 parls—books, tools, ete. Every- thing you need in onc complete book, Lowest prices, fastest service, SEND COUPON for Free new Catalog. FREE PARTS LISTS—Write for Free parts lists for any kit described in this or in any other magazine, My Personal service assures strictest con- fidence on all your PERSONAL SERVICE patent problems, Send me a model or draw- ing, or sketch and description of your invention, and $5.00. I will make a search and report promptly as to its patent- ability and send you a copy of my 72-page booklet. Or, if you prefer to read my booklet first, write today for FREE copy. Registered Patent Attorney. L. F. Randolph, 761 Victor Building, Washington, D. C. | Print YourOwn | Only Boats With Cards, Stationery, Advertising, labels, paper, circulars, tags, ete, Save money and time. Sold direct from factory only. Junior Outfit Full Length Spray Rails Keep passengers perfectly dry—even at high speeds. Catalog also shows today's five most popular models of sailboats. Two big facto- ries. Prompt shipment. Write p CATALOG FREE sof Boutin which yon are interested. © Veryfastutllity model THOMPSON BROS. BOAT MFG. CO. (87 230 Ann St., ( Write to 230 Elm St., PESHTIGO, WIS. either place, CORTLAND, N. Y. 132 $9.00. Senior oulhts $17 and up. Do popular ralsed printing like engraving with any of our presses. Print for Others, Blig Profits Pays for itself in a short time. Easy rules sent. Write for free catalog of outfits and all details. KELSEY PRESSES, D-9 Meriden, Com. cone Better Built Lower Prices Men Behind The Stop Watch [Continued from page 60] gasoline tank was filled, locked, and the key handed to the A. A. A. observer. The car then rolled out of the garage to begin its leisurely drive from New York to San Francisco. Anxious to test the gasoline consumption at ordinary driving speeds, the pilot was in no hurry. Forty- five miles an hour was top speed. Fifty-one stops were made along the route to eat, sleep, refuel, or take pictures. At each refueling, the observer unlocked the tank, relocked it, and re- turned the key to his pocket. The whole trip con- sumed about 811% hours’ running time, although 102 hours were actually spent en route. A. A. A. men, computing from their records, found that in its 3114-mile run the car had averaged 21.421 miles to the gallon, consuming slightly more than 145 gallons of gasoline. Still carrying A. A. A. observers, the car then turned its nose toward Muroc Lake—a natural race-course laid out upon a barren plain, miles in extent, smooth and bare as a billiard table. At 9:27 in the morning, with the thermometer standing at 118 degrees and no wind stirring, A. A. A. timers started their electrical timing system as the car rolled across the starting line. Gulotta and Hartz, well-known racing drivers, alternated during the gruelling 28-hour stretch. Not a breeze drifted across the great tawny Mohave desert. Torrid waves of heat radiated into aching eyes and on blistering skins. Through the night, with torches marking the boundaries of the course, the car roared on, and on into the day. Finally a timer stepped to the edge of the course and raised a chalked sign above his head, notifying the driver to come in. As the car passed over the finish tape, A. A. A. officials took slide- rules and computed that a brand-new series of records had been established. Thirty-two old records had been shattered, many by as much as 10 miles and hour. The sedan averaged 80.88 miles per for the first ten miles, 74.74 over the entire 2,000 miles. Practically all the important speed records of the present have been made with A. A. A. men computing the figures. Use of electrical timing mechanisms have made their computations sufficiently accurate to be used as standards of motorcar performance. Even the betting fraternity respects the races held under A. A. A. super- vision, for they know that decisions will be fair and impartial. Choose The Right Brush [Continued from page 97] a wide brush to finish inside a narrow or cramped space. or the bristles may become ruined by such treatment. Ordinary paint should be werked into the pores cf the work, and for this reason professionals adopt a routine of brushing back and forth with the grain, until the paint is well distributed; then they work across the grain, and finish with light strokes with the grain. Like any cther tool, a brush is subject to gradual wear; for this reason it Accept No Substitutes! Always Insist on the Advertised Brand!

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should be turned occasionally so that the wear will be even and the shape preserved. Painting a very uneven or rough surface will wear down the bristles faster than if the surface had been properly prepared beforehand. The method of applying varnish or enamel, which have similar characteristics, is quite different: the finish is flowed onto the surface instead of being worked into it. Do not make the mistake, however, of trying to flow a number of coats on at one time; a number of thin coats result in a much more presentable and durable finish. It is in varnishing and enameling that the dusting brush shows its great value. Use it to clean all loose particles of dust from the work immediately ahead of the brush, and to clean out corners and crevices. Also, if particularly clean-looking work is desired, work all loose bristles from the brush beforehand, and soak it overnight in a cup of varnish, It has been mentioned that professional decorators think of the purchase of a high quality brush as an investment, for they expect it to give good service for a long time. The investment is protected, however, only when the brush is given careful treatment, and particularly important is the care used in cleaning it after it is used each time. More good brushes are ruined by lack of cleaning, or by improper cleaning, than will ever be worn out by amateur decorators. One cause of brush failure is the entrance of moisture into the inside of the bristles, as this quickly softens them and removes the elastic springiness that makes for good work. Keep it in a dry but not warm place, inside its keeper if one was provided when you made the purchase. An excellent keeper can be made by folding a shect of Cellophane around the brush, folding up the end and snap- ping it in place with a rubber band. ‘his protects it from both dust and moisture, and at the same time keeps the bristles nicely in alignment. Do not submerge the binding of the brush in the paint, and never allow the ends of the bristles to rest on the bottom of the can. ‘Turpentine or gasoline can be used to clean a brush of ordinary paint, but many professionals prefer ordinary gasoline (and not the kind containing lead) because it is less expensive and evaporates more rapidly. The important point is to wash all of the paint from the brush and from each individual bristle. Your good brush will not last if you do not. A good method is to use a coarse comb to separate the bristles up near the heel (next to the binding) so that the gasoline can enter freely. If old paint is allowed to accumulate in the heel, the bristles eventually will spread out. After it is thoroughly clean, whisk it about and use the comb to line up the hristles in case they are not straight. If you do not intend using a-brush for a considerable period of time after cleaning it, a good plan is to anoint the bristles with light lubricating oil, This will keep out moisture and preserve the suppleness, and the oil can easily be removed with gasoline when you wish to paint again. Some decorators wash their brushes with soap and water; it is not a practice to be recommended, but if it is done at all a good mild soap, such as soap flakes, should be used. Be sure to dry the brush thoroughly befere putting it away. Varnish and enamel brushes should he cleaned with tur- pentine as gasoline has a tendency to curdle some types of varnishes, making the substance very di Jt to remove. Be sure to dry out a turpentine-cleaned | thoroughly before using it again, as the small amount of s-lvent remaining in the heel would otherwise caus zish to bubble and foam in the brush as it i aplied. Alcohol is the proper cleanser for shellac and it can sometimes be used for those that have 1} d for lacquer, although the regular lacuuer thinner Be very careful not to clean a brush near an ope If it is necessary to ciean brushes quite often, a ¢ n is to keep the solvent in a container that can be tigli Between cleanings the paint material will have set and the clear solvent can be poured off, to be used over over again. Kalsomine brushes should be cleaned in a solution of one part vinegar and two parts of water. and this is also useful as a dip when the brush is to be sed for a short length of time. The action of the vinegar is to neutralize the alkali of the finishes of this type, which would otherwise attack the bristles. NOTICE Changes in the make-up and title of this magazine, designed to make your favorite publication better than ever before, will be- come effective with our next issue. Be sure and reserve your copy now. Our new name will be—“Mecuanix ILLUSTRATED.” When Answering Advertisements Picase Mention May Modern Mechanix This | MACHINISTS’ | Home-Study Course helps men get ahead _ Newly assembled—specially priced—these fire recent hooks give you the practical facts on modern machines, up-to-date methods you need to advance in machine shop work, Take advantage of the other man's experience as found in books, to solve your problem, increase your efficiency, with the new Library of Modern Machine Shop Practice 5 volurnmes—2000 pages—1600 Illustrations (A combined home-study course and reference library) This llbrary of machine shop practice was written for practical men. It gives you the best methods for every kind of machine shop work. It deals fully with lathes, drills, and other machine tools and their operation, automatic serew machines, speeds and feeds, gear design and production, punch and die work, metal finishing, ete., ete, Plainly wriltten—completely illustrated—the best kind of help to the machine-shop man who wants to advance himself, No money down-—special price—easy payments FREE EXAMINATION COUPON McGRAW-HILL 800K CO., Inc., 330 W. 42nd St, NEW YORK, N. Y. Send me for 10 days’ free examination the Library of MODERN MACHINE SHOP PRACTICE. If satisfactory I will send $1.50 in 10 days and $3 monthly until the special price of $16.50 is paid. Jf not wanted, I will return the hooks postpald. (To in- sure prompt shipment write plainly and fill in all lines.) Addvess.__._ City and State Position PAYS BIG! An opportunity to earn up to $2 to $3 an hour in your own cash business. Start in spare time at home. No experience required. You can do expert work...easily, quickly, without eye- strain, with a AUTO- FOLEY MATIC A SAW FILER ‘IN “I have filed 765 saws in spare time and have earned $850.00 tn carpenter work due directly to my saw fillng contacts,” says Louis P. Wadowick, Ohio, ‘‘Am still operating my Foley Filer after 5 years, Business better than ever this year,’’ writes J. W, Veith, Pa, The Foley files ALL kinds of hand saws, band saws and cross- cut circular saws BETTER than expert hand filing—erery tooth exactly uniform In size, FREE PLAN shows you how to start—no canvassing. Send coupon now—no obligation, no salesmen will call. — eee eee ee ee ee FOLEY MANUFACTURING CO. : : 506-8 Foley Bldg., 11 Main St., N. E., Minneapolis, Minn. Send me FREE PLAN, for starting my own business in spare time filing saws on the Foley Automatic Saw Filer, without obligation to me, 133

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( Monastery : Secrets . . . THE FORBIDDEN & KNOWLEDGE OF TIBET What strange secrets of nature are locked within the mountain fast- & ness of ‘Tibet? What control over | the forces of the Universe do these cloistered sages exercise? For cen- turies the world has sought to know the source of their power—to learn their mastery of life, and their faculty for overcoming problems with which $ the masses of mankind still jÆ struggle. Have they sel- fB fishly deprived humanity $ of these rare teachings? WRITE FOR THIS FREE BOOK Like the streams that trickle from the Him- alayan heights to the plateaus below, ihe fy greatiruthsofthese KẸ brotherhoods have descended through the ages. One of the preserv- ers of this wisdom of the sages is the Rosicrucian Brotherhood (not a re- ligious organization). They invite you to write today for | their FREE Sealed Book, ¥ withits amazing revela- tions about these mys- teries of life. Address: Scribe C.N.V. The ROSICRUCIANS AMORC SanJose,Calif. ,EARN MONEY Make Color-glazed Concrete Products New, perfected low cost methes. costly tools. You build your own e e casting, eiftware—in hor ar joney. MEN—Send 10e TODAY for colnrplate, detalls of this money making z. No oblice gation. NATIONAL POTTERIES COMPANY Room 8, 13 W. 26th St. Minneapolis, Minn. the major tool of science, is a fascinating and educational home hobby for thousands. You, too. can explore the mysteries of the un- seen world, through the magic of the microscope. Bausch & Lomb precision amateur microscope Model R (left), 75 to 300 power; with 455-page Fx book, $21. Other models, $14.50 up. / SEND FOR FREE BOOKLET pe? (right). Bausch & Lomb Optical Co., 243 Bausch St., Rochester, N. Y. ZA BAUSCH & LOMB T 134 Cut Sections For Microscope [Continued from page 86] if it does not work freely, lap it to fit with valve- grinding compound. A radio dial of suitable size and marked into 100 divisions can be purchased cheaply; or it can be turned on a lathe. Dividing the circum- ference into 100 divisions is not difficult. Lay it out on paper first, quartering a circle with two diameters at right angles to each other. Use a pair of dividers, and by trial and error divide each quarter into five divisions, then each of these in turn into five. Stick a pin into the center of the drawn circle, lay a steel rule against this pin and draw lines from each of the 100 marks in to the center. Now affix the paper circle to the wooden dial temporarily with rubber cement and mark the divisions on the wood with a very sharp pencil. Remove the paper and give the dial two coats of shellac. The dial is now mounted on the end of the screw-rod, using care to get it just at a right angle so that it will not wobble when turned. To the other end of the wooden block is fas- tened a metal or plate glass piece drilled to fit tightly around the brass tube, which is then cut and filed to be precisely flush with the plate’s surface. Glass is best for smoothness and flat- ness and may be drilled by another length of the same brass tubing used in making the microtome well. A very thin film of Plasticene modeling clay may be employed to hold the plate to the wood; this permits some adjustment should trial cuts prove that the plate is not at an exact right angle to the tube, which it must be. Various cements may also serve. It can now be seen that when a specimen is placed in the tube and the dial turned so as to bring it to the surface ready for sectioning, a turn of one division on the dial will push the specimen upward by 1/100th of the thread of the screw- rod. If this is the usual 14x20 bolt, the move- ment will be 1/100th of 1/20th of an inch, which is 0.0005 inch; if finer threads have been used, then it will be 1/100th of however many threads there may be to the inch. On the model pho- tographed it was perfectly possible to estimate 12 of a division, thus reducing the movement, and hence the thickness of sections cut by this in- strument to 1/200th of the thread. By such means one can tell fairly accurately the thick- ness of his sections. i During the cutting process, this well micro- tome may be held in the left hand and the razor manipulated with the right, as described for free- hand sectioning: It will be better, however, to place the block on a table, hold it steady with the left hand and cut with the right hand in the fashion of chopping, using a sliding stroke, from toe to heel of razor and taking care to keep the blade pressed against the cutting plate. The measurement of extremely small dimen- Accept No Substitutes! Always Insist on the Advertised Brand!

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sions, as seen under the microscope, constitutes the science of micrometry, and the unit of meas- urement is the micron (plural, micra), abbre- viated by using the Greek letter mu (equivalent to our m). This is one-thousandth of a milli- meter (0.001 mm) which in turn is one-thou- sandth of a meter. A meter is 39.37 inches, hence a millimeter is 0.039 inch and a micron is 0.000039 inch, a very minute measurement in- deed! Routine machine microtome sections, in schools and hospital laboratories are customarily cut at 10 micra; those to show detailed parts of cells, at six, five or even less. It is perfectly pos- ible, with the best equipment and a certain ' amount of skill that comes with practice. to cut sections as thin as a single micron. Hand microtome sections may be cut as thin as 10 mu but more often are thicker and free-hand sections are almost always considerably thicker. This does not mean that they are inferior to ma- chine cuts, for it is not always desirable to have sections as thin as 10 mu; it all depends on the material being sectioned and the purpose for which the sections will be studied. For the gen- eral anatomy of plant buds, stems, roots and many other items, sections of 25 mu may surpass thinner ones in explaining relationship of parts and the structure of the object as a whole. If the hand microtome is used, the material must be held firmly in the well and against the bottom plate, so that turns of the dial will push it upward for successive cuts. Large objects are trimmed down to fit in the well and then they, as well as all smaller materials, are surrounded and supported with certain packing material, in- cluding strips of wood pith, raw carrot or turnip, or hardened beef liver. Strips of beef liver measuring something like two inches in length by one-half to three-fourths of an inch each in breadth and thickness are placed in alcohol for 24 hours, then transferred to fresh alcohol and kept until needed; this renders the liver suitable as to hardness. Place any of these fillers in the well, surround- ing the object and reinforcing it, and reaching to the bottom of the well, leaving no waste spaces. The filler is cut along with the object, but separates readily when the whole section is floated in water. For very small objects—and many technicians prefer the method for all ob- jects—imbedding is necessary. Use a mixture of three parts of melted paraffin, any of the com- mercial brands used for sealing jelly glasses, to one of vaseline, thoroughly stirred together while heated just enough to keep the paraffin melted. Do not “cook” the mixture; the warming is best done on a slide dryer or over a radiator, an elec- tric bulb inside a ventilated tin can, or other source of mild heat. To imbed a tree bud, for example, warm the microtome first then fill the well with the melted imbedding mixture; blot the bud or dry it on a cloth should it be wet, and when the paraffin has [Continued on page 141] You get the same uniform strength in bottle, tube or can of LePage’s— standard throughout the world. The economical fixer. g Fool of 100! Uses A WHOLE SHOP FULL OF TOOLS IN ONE For work on all metals, alloys, bone, resins, plastics, glass, Æ stone, wood, etc. Uses 200 È different accessories to grind, drill, cut, carve, sand, saw, engrave, sharpen, clean, polish, etc. Saves hours of tedious hand work. Plugs in any socket AC or DC, 110 volts. STANDARD MODEL A sturdy little helpmate. Weighs 1 pound. 13,000 r.p.m. $10.75 postpaid, 3 Accessories Free. DE LUXE MODEL Faslest, most powerful tool of its type and welght, 12 ounces, 25,000 r-p.m. $18.50 Postpaid, 6 Accessories Free. GET A DEMONSTRATION at your Hardware, Department ar ‘Tool Dealer or order either Model on_10- Days, Money-Back Trial, Catalog Free, CRAFTSMAN’S PROJECT BOOK Easy working plans for making many ln- teresling and unusual projects, 25e slamps or coin. Chicago Wheel & Mig. Co., 1101 W. MonroeSt., Dept. H, Chicago, II. O $10.75 Model O Project Book Send Catalog O De Luxe Model When Answering Advertisements Please Mention May Modern Mechanix D Sena ©. 0. D. MMI-5 135

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ATTENTION Bargain Hunters! Fac- tory rewound 110 volt, 60 cycle A.C. generalors, 175 to 1500 watts, Also slow speed 6, 12 and 32 volt D.C. generators for wind light plants and wind chargers. Sold for rewinding costs. Guaranteed. Monroe Mig. Co., Box 3343, St. Paul, Minn. PRACTICAL changes for automobile generators. A. C. and D. C. generators, motors and welders. Complete wind and water power plants. See our ad- vertisement at bottom of page 11. Autonower. A. C. Generators, hand-driven, gen- erates 110 volts, original price $5.50. Special 98c. Electrical Salvage, Box 524-81, Lincoln, Nebr. ADVERTISING AGENCIES YOUR Ad in 1,500,000 Sunday News- papers (guaranteed, national circula- tion) $15.40 inch. Rate-book all leading newspapers, magazines, Free. Chicago Advertising Agency, 20-M West Jack- son, Chicago. ADVERTISE: 24 words in 250 News- papers $10. Lists Free. Advertising Service Bureau, 4515-B Cottage Grove, Chicago. 33 WORDS, 25 Magazines, Three Months, $2.00. Goodall Agency, 742 Market, San Francisco. FREE NEW advertisers rate guide. Brown Advertising Agency, 140 South Dearhorn, Chicago. AGENTS WANTED AGENTS: Smash go prices! Santos Coffee 12c 1b. 4-0z. Vanilla 814c. Razor Blades 10 for 8%c. 100 Sticks Chew- ing Gum 12c. 150 other bargains. Premiums. Experience Unnecessary. Carnation Co., MN. St. Louis, Mo. IF EARNINGS up to $45 first week will satisfy you, I'll send complete out- fit to run home-operated Grocery Agency. Absolutely no money Details sent free. Write Albert Mills, 6203 Monmouth, Cincinnati, Ohio. PROFIT with new products. Make, sell, repeat.. Analysis. Research. Guar- anteed formulas. Biggest catalog free. Special prices, leads. Gibson Labora- tory, Chemists, CE-1142 Sunnyside, Chicago. BIG MONEY Taking Orders; Shirts, Ties, Hosiery, Underwear, Raincoats, Pants, Uniforms, etc. i FREE! Experience unnecessary. Write NIMROD, Dept. 132, 4922-28 Lincoln, Chicago. BIG Money applying initials on auto- mobiles. Easiest thing today, Free samples. Also, sideline salesmen for name plates and tire cover transfers. ALEON 1305 Washington, Boston, ass. MAKE Easy Money. Polish. Exclusive Territory. Package makes half gallon, cost $1 dozen, sells $6 dozen. Sample 25c. A. A. Supply Co., 422 Turk St., San Francisco, Calif. LARGE Profits in your own business. Sell new and used clothing, bankrupt stock. Experience unnecessary. Every- ‘hing furnished. Details free, Publix, 558-KT Roosevelt, Chicago. 136

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with motor Easy terms—

BIG money applying initials on auto- mobiles. Write for particulars and free samples. American Letter Company, Dept. 11, Dunellen. New Jersey. 500% PROFIT Selling Gold Leaf Letters for Store Windows. Free Samples. Metallic Co., 445 North Clark. Chicago. ATLAS Window Sign letters. Large Sizes, Penny Each, Beautiful Free Samples. Atlas, 7941-G Halsted, Chicago. MEXICAN Curios, tremendous money- makers! Samples 10c. Marquez-M, Apartado 1176, Mexico City. AIRPLANE ENGINES CONVERTED two-cylinder Lawerance Aircraft Engine $60. Write for par- ticulars. Albert Cartwright, 405 Whit- ney Ave., Fresno, Calif. AMERICAN POLICE JIU JITSU 13 KNOCKOUT Blows without use_of

fists, by internationally famous Jiu Jitsu instructor. Send 15 cents. S. J. Jorgensen, 293 Maritime Building, Seattle. Washington. ARG WELDERS 75-200 AMPERE are welder from Dodge generator. Complete plans and valuable catalog 35c. 100 other gener- ator changes. Lelay Manufacturing, 214 LeJay Bldg., Minneapolis, Minn. ART MAGAZINE ART MAGAZINE. Helps you sketch human figure, paint, model, carve, cartoon, sell drawings, exhibit, form clubs. Regular 50c value—two for 25c while samples last. Magazine, 320 West Doty. Madison, Wisconsin. AUTOMOBILES ECONOMY! Performance! Mileage! Semi-diesel conversions for gasoline motors, $5.00 up. Manufacturer’s writlen guarantee. Learn basic facts from free literature. Houston & Logan Conversions, 1719 Addison, Berkeley, California. AUTO SUPPLIES & EQUIPMENT CONVERT your car to burn Diesel oil. Save up to 70% fuel costs. Cheap in- stallation. Wonderful performance. Proven factory method. Different and hetter. Costs nothing to investigate. Write for free circular No. 5A. Har- rington Company, 201-204 Manchester Building, Portland, Oregon.

INEXPERIENCED workers, apply for aviation jobs now. Fall salary while learning. Details for stamp. <Airploy- ment, Box 553, West Los Angeles, Cali- fornia. HEATH Airplane, motor, propeller literature, dime. Heath _ Aviation Company, Benton Harbor, Michigan. BLUEPRINTS METAL TUBE Midget Radio, the last word in compact radio receivers. You can construct this set even though your knowledge of radio is limited by follow- ing the large pictorial blueprints avail- able, from Modern Mechanix Publ. Co., Greenwich, Conn.. at 50c postpaid. MAKE your own 100% reverse gear from auto parts, $5.00. Arc welder from Radio Junk, $1.00. Current limiting device, $1.00. Krehs, 19 Wol- cott St., Brooklyn, New York. BOATS LATEST Boat Sensation: New 20 Ib. Mead Sportsmans Ki-Yak assembled at home easily, quickly from complete factory-cut kit. $6.00 paddle now given with yours—if you hurry! Rush dime for catalog with pictures, description i.e. Mead Gliders, Dept. MC-58, Chi- cago, Ill. FORD and Lincoln Marine Conver- sions. Send 10c for information. Lehman Engine Co., Newark, N. J. BOOKS & PERIODICALS SPORTSMEN’S MANUAL—The out- doors man's guide containing scores of practical articles by America’s leading outdoor writers, covering every phase of fishing, hunting, camping, and trap- ping. This book, edited by Robert Page Lincoln, will make that next vacation a dozen times more enjoyable. Price 50c at your newsstand, or order directly from Modern Mechanix Publishing Co., Fawcett Bldg., Greenwich, Conn JUST Published: 1938 Directory of Hobbies and Spare-time Opportunities. A guide for amateur and professional hobbyists. 25c per copy. Park City Book Supply, Dept. W, 1078 Pembroke Street, Bridgeport, Connecticut. BUSINESS OPPORTUNITIES GLASS-LIKE Color Glaze for con- crete, pottery, tiles, blocks, walls. Ex- clusive, patented process. No experience needed to make 2,500 designs glazed pottery without molds. Build your own equipment from our plans. New, money-making business for men. Color- plate, booklet, details 10c. None free. Write. National Potteries, 13 West 26th St., Minneapolis, Minn.

Accept No Substitutes! Alccays Insist on the Advertised Brand!

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Hand Saw Features Two | Sets of Teeth Designed for use as either a cross-cut or rip saw, a new hand saw produced by an Indianapolis, Ind., manufacturer has teeth that are somewhat larger than the usual variety and arranged in sets of three. Two of the teeth in each set are slicers, or cutting teeth, and the third is called a planer. The slicer teeth make the cut and the planer cleans it out and levels, Preventing binding of the blade at any time. A suitable gauge (shown in use above) is provided with each saw so that any- one can file the teeth accurately with- out difficulty. PLASTEX Industry needs manufac- turers on small scale and fcr big pro- duction of Art Goods and Novelties in Plastex and marble imitation. Cheaply and easily made in our guaranteed rubber moulds. We cooperate in selling goods. You are just in time for big 1938 wholesale season now starting. Interesting booklet mailed free. Plastex Industries, Dept. R, 1085 Washington Ave., New York. A BUSINESS for country cr_ city, electric fire and burglar alarm. Profits galore. Directions, package equips five windows, one door, $8.00. Each addi- tional openings thirty cents extra. Not including wire. Mention whether elec- tricity is available. Hart Alarm Ce., 3029 Lorain Ave., Cleveland, Okio. FASCINATING business. Rerair, ad- just typewriters, add machines. Learn easily at heme cm factory | expert. Earn up te $ Com- plete instructions ccv i makes $3.00 postpaid or sen: C. o Adding Machine Equipment $ 3601 Michigan, Dept. 2045, WE START you in ing Outfits and Instruc “Specialty Candy Factory and women, earn $25.00 wur weekly, all or spare time. ‘ year.) Booklet Free. W. Hil oe Inc., Drawer 110, Eas: Parts, Reflectors, Bicycles. Mirrors, by late method. of manufacturing at heme in Good Paying Business ticulars and procfs. G Ave. A. Decatur, Illinci MAKE artificial m uncanny. Tabletops. hones, novelties. Hard, pensive, cement secrets. E: and liquid rubber samples 3c. Payn, 945 Grande Vista Aver Angeles. Calif. LIKE To Write? Earn Clipping and preparing newspaper articles for publishers, Simple, fasci- nating, profitable, Stamp brings details. extra cash!; ‘ Jand, Hollywood, California. H PROFIT with new products. Make, sell, repeat. Analysis. Research, Guar- : IF YOU are looking for a chance to | prise. j Accurate analyses. | FREE LITERATURE describes hun- ' cr equipment in trade, Division 76, National Press, 3923 West Sixth, Los “Angeles, California. When Answering Advertiscments Please Mention May Modern Mechanix COLOR concrete surface with chemical | solutions. Beautiful pottery without moulds, Garden wishing-wells. Stucco rock. Glazing concrete. Sample 10c. Hollywood CementCraft, 8528 Wonder- : anteed formulas. Biggest catalog free. Special prices, leads. Gibson Labora- tory, Chemists, CE-1142 Sunnyside, Chicago. devote your spare or full time to profit- able work see our offer on page 26. Metal Cast Products Co., 1696 Boston Road, New York City. GREAT Money Making Opportunities. Start mail order business of your own. Spare time. Make money. Write, Process Co., 4437 N. Lincoln Ave., Chicago, Ill. AFTERNOONS free for movies. $340 month, home. plan. No canvassing. Prepare for sur- Folio-S, Station D, Los Angeles. SUCCEED With Your Products. Make- Sel) Them. Formulas. Processes. į Catalog free. A. Thaxly Co.. Washington, D. C. IF YOU'D like an extremely profitable, ; lifetime business, operate a Collection- Credit agency. Free folder. Cole Associates, Syracuse, N. Y. i YOU'LL Like Resilvering Mirrors, Autoparts, Reflectors, Making Chipped Glass Signs. Write Sprinkle, Plater, 845, Marion, Indiana. MERCHANTS attention. Proven sales ideas that bring real business. Sen $1.00 for three. W. S. Finigan, Oneonta, N. Y. PLANT Chemiculture. Instructions, 10 formulas, $1. Dawson_and Dorn, 4615 W. Washington Bivd., Los! Angeles, AGENTS—To mail cur literature. Good profits. Home business, M. Maywood. 149 Fifth Ave., New York. SELL by Mail! Books, Novelties! Bar- gams! Big profits! Particulars Free! H. Elfco, 438 North Wells, Chicago. EARN cash income, copying and dupli- cating simple cartoons for advertisers. 3-N_Service, Argyle, Wisconsin. HOW and where to obtain capital fully explained. free particulars. Star Service. Wapakoneta, Ohio. j WANTED—Columbus ball gum vend- ing machines. Postal Bex 1014, San Antonio, Texas. OPPORTUNITIES. Men, women. Literature. Silvester & Cc., MM, Old | Bridge, N. J. i 107 NEW successful home business l pans Century, 1261-M Broadway, | Nis + i CAMERAS & PHOTO SUPPLIES CAMERAS and supplies. Free illus- trated catalog listing everything photo- graphic—still. and movie cameras, films, lenses—at tremendous savings. Haun- dreds of bargains, new and used. All guaranteed. We take your old camera Write now for your free copy of our newest money- saving bargain hook—just out! Limited ecition. Hurry! Central Camera Co. (Photographic Headquarters Since 1899), 230 South Wabash, Dept. 5-J, Chicage. Shaper Features Tilting Table Featuring a tilting table which is raised or lowered on an accurately ground column, a new shaping machine makes it possible to cut bevels and intricate moulding with standard shaper knives. Manufactured by a Wisconsin firm, the shaper can be had as a bench or floor type. MAKE money in photography, Learn quickly at home. Spare or full time. Easy plan. Previous experience un- necessary. Common school education sufficient. Interesting booklet and re- quirements free. American School of Photography, 3601 Michigan Ave., Dept. 2049. Chicago. INCOME From your camera instead of expense. Low cost home course teaches you to make photographs for magazines, newspapers, advertisers. Tremendous demand. Earn good money wherever you live. Free book. Universal Photog- raphers, Dept. A, 10 West 33rd St. m New York. CASH for used cameras, lenses. S for appraisal or describe fully. Miller Photo Service, Avoca, New York. DUPONT Superior Panchromatic, 35 mm; 25 ft. roll, $1. Optical Labora- tories, Larchmont, N. Y. CHARTERS DELAWARE Charters: Complete in- corporating and organizing service $35. Submitted forms. Chas. G. Guyer, Inc., Wilmington, Delaware. CHEMISTRY EXPERIMENTERS—Join American Amateur Science League, West Chester, Pennsylvania. Particulars sent free. CHEMISTRY, Mineralogy, scopes, Binoculars. Catalog Teeko, 5315K, Evanston, Illinois. CORRESPONDENCE COURSES 500,000 USED Technical and business Sold, rented, exchanged. All subjects. Satisfaction guaranteed. Cash paid for used books. Complete details and illustrated bargain catalog free. Send name. Nelson Co., 3229 Man- hattan Bldg., Chicago. DETECTIVES DETECTIVES. Make Secret In- vestigations. Experience unnecessary. Detective Particulars Free, Write, eorr Wagner, 2640-V Broadway, N. Micro- Free. 137

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Refrigerator Light Operates on Battery Designed for refrigerators operated by gas or using natural ice, this small battery-operated light unit can be in- stalled in a few minutes. The unit is held against the ice box ceiling by two suction cups and the small spring, ex- tending forward and down from the front to contact the inside of the door, acts as a trigger to snap the light on or off as the door is opened or closed. BE A DETECTIVE. Make secret in- vestigations. Excellent ‘opportunity. Free particulars. Raymond Stultz, Box 633, Elkhart, Indiana. EDUCATIONAL & INSTRUCTION MEN Wanted—Learn ‘Tool & Die Making. Automatic Screw Mach. Machinist Trade. Big Demand. Actual Experience. Expert Supervision. Write for Free Book “M”, Allied Screw Machine Co., Inc., School Div., 603-9 Lake Su. Chicago, WANTED Immediately, Men-Women, age 18-50, qualify for Government Posi- tions. Commence $105-$175 month. Common education sufficient. Valuable information free. Write, Instruction Service. 234, St. Louis, Mo. PRACTICAL Arithmetic, Algebra, Geometry, Slide Rule, for shop arl office. Simplified Short Cuts. Complete Course $1.00. Slide Rule Free. Mathe- matics Press, Box 434A, Duluth, Minne- sota. “UNCLE SAM” 1938 Jobs. $105- $175 month. Particulars—list positions —sample coaching free. Write Frank- lin Institute, Dept. R59, Rochester, Y. ELECTRIC FENCING MAKE Electric Fencer. It’s easy with our simple plans to convert Ford T coil. No further costs. Complete plans 35c. LeJay Mfg., 814 LeJay Bldg., Minne- apolis. Minn. ELECTRIC PENCIL ELECTRO-SCRIBE: Electric Pencil. Writes—Engraves all Metals. $1.00 postpaid. Details Free. Beyer Míg. Co.. 4515-Y Cottage Grove, Chicago. EMPLOYMENT SERVICE EMPLOYMENT Guidance. Booklet. Successful Job Hunting. 25c coin. Employment Counsellors, Box 1283B, Milwaukee, Wisconsin. JOB-HUNTERS !—Hit-miss useless. Valuable check-list ways to get job. 10c. Employment Aids, Box 535, Peekskill, N. Y. 138 methods ENGINES, MOTORS, ETC, WINDING Data, 225 motors, single axd three phase. Price $1.06. Motor Data Service, Box 7631, Kansas City, To. EXTERMINATING COCKROACH, Bedhug Exterminator. 25c makes gallon, which regularly sells for $2.50. Formula 25c. Tom Moore, Chemist, Waterloo. Iowa. FARMS 40 ACRES, Near White River, un- improved; poultry land. $175, $5 down, $5 monthly. Free list and literature. Hubbard, 224 Grossman Bldg., Kansas City, Kansas. FEMALE HELP WANTED WEAR fine hose I send without cost with outfit while taking orders for amazing new hosiery. Replacement guaranteed against holes, snags, and runs. Rush name and hose size. Wil- knit, Desk 34-E, Greenfield, Ohio. FOR INVENTORS PATENT Your Idea. Write imme- diately for two free books, “Patent Protection” and “When and How to Sell an Invention.” Fully explain many interesting points to inventors and illustrate important mechanical principles. With books we also send “Evidence of Invention” form. Prompt service, reasonable fees, thirty-nine years’ experience, Avoid risk of delay. Address: Victor J. Evans & Co., Registered Patent Attorneys, 42-E Vic- tor Building, Washington, D. C. INVENTOR'S Universal Educator; contains 900 mechanical movements; 50 perpetual motions; instruction on pro- curing and selling patents and selecting an attorney, etc. Suggests new ideas. Price $1 postpaid in U, S. A. Address Albert E. Dieterich, 511R Colorado Blide.. Washington, D. C. FREE Booklet (copyrighted) for in- ventors wishing to sell, Explains market- ing facts and buver locating method that may save costly mistakes and lead to profitable sale of your patented, un- patented invention. For Tree copy write: Invention Reporter, E-11236 So. Fairfield, Chicago. INVENTORS: Send for my free 72- page book. Conscientious, prompt per- sonal service on all patent mutters. Registered Patent Attorney, IL. j kandolph, Dept. 341, Washington, WC. WE SUCCESSFULLY sell inventions, patented and unpatented. Write for proof, and tell us what you have for sale. Chartered Institute of American Inventors, Dept. 3-B, Washington, D. C. FORMULAS, PLANS, ETC. ANALYSIS. Research. Newest guar- anteed formulas. Biggest catalog free. Special srices, leads. Gibson Labora- tory, Chemists, CE-1142 Sunnyside, Chicago. SUCCEED With Your Products. Make- Sell Them. Formulas. Processes. Accurate analyses. Catalog free, A. Thaxly Co., Washington, D, C. ANY formula 25c. Two hundred as- sorted one dollar. Guaranteed. Walter, Box 527, Bridgeport, Conn. PROVEN Money-making Formulas. Free Literature. Broukins, Box 82, Stoneham, Mass. FORMULAS—Latest Money Makers. Literature free. D-Belfort, 4042 N. Keeler, Chicago. FORMULAS—AIl kinds. Guaranteed. Catalog Free. Kemico, 67, Parkridge. Illinois. Metal Camera Mask Cuts Picture Cost Designed for use with 3A Kodaks, Series II, a newly developed “twin- exposure” camera back enables owners of such cameras to cut their picture- taking costs almost in half. The new back enables eleven pictures of a 2x3 %-inch size to be taken on a roll of regular six-exposure film of the size used in the 3A. The back can be installed at any good camera shop in a very short time. GARDENING Formula and $1. NU-SOILS, 42A Sun Building, Jack- son, Michigan. HYPNOTISM. Complete 20 Method Course 25c. Western Institute Iypno- tism, MM-2984 North Ridgeway, Chi- cago. INVENTIONS 8 es a PENDING Patents can be made more salable than issued patents. Pay only Government filing fee. Explanatory booklet free. American Patents Corpora- tion, Dept. 5-F, Washington, D. C. INVENTION S—Patented, Unpatented, Bought outright, royalty. Write Arel- lano-Power Company, 1 North La Salle St., Chicaga, Tllinois. INVENTORS: Write for free copy “Pointers on Promoting Inventions.” National Service Bureau, Dept. M, St. Louis. Mo. INVENTIONS WANTED SMALL inventions wanted by manu- facturers. I’ll help you sell your in- vention. Write for free circular. 5. Hull, 7829-L, Euclid, Avenue, Cleveland, Ohio. INVENTIONS quickly commercialized. Unpatented protection guaranteed, Pacific Inventors Agency, 2236 Post, San Francisco, Calif. INVENTIONS Commercialized. Pat- ented or unpatented. Write _Adam Fisher Co., 582 Enright, St. Louis, Mo. INVENTORS CASH for Unpatented or Patented inventions or ideas. Stamp for par- ticulars. Mr. Ball, 9441-F Pleasant, Chicago. GET Your Own Patents. Legal blanks, complete instructions $1. Cudding Sons, Campbell, California. MACHINERY, TOOLS & SUPPLIES MOTOR Speed Reducer ratio 144 to 1, rating up to 4 h. p. with friction clutch for overload- protection—$3.95. Send for free catalog: Compressors, Paint Sprayers. National _Electric Tool Co., 560 Washington, Chicago, Accept No Substitutes! Always Insist on the Advertised Brand!

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Auto Vanity Mirror Has Built-In Light Shaped to fit the hand, a newly de- veloped vanity mirror for feminine motorists features a built-in lamp which floods the user’s face with a beam of soft light. The lamp is connected by an extension cord to an electrical outlet on the auto and is controlled by a tiny switch.’ MICROMETER: $1,50 postpaid. Ac- curate measurements by thousandths, 0-14 inch with instructions. Also one inch size with adjustable anvil, $2.65 postpaid. W-Box 3432 Merchandise Mart, Chicago. MAGIC TRICKS & NOVELTIES FREE! Magic Catalog 500 Tricks. Amaze, Mystify friends. Write today! Lyle Douglas, Station A-3, Dallas, Texas. WE SUPPLY every noted magician, Large Professional catalog 25c. Holden, 222 West 42nd St.. New York. MALE HELP WANTED STEADY Work—Good Pay—Reliable man wanted to call on farmers. No experience or capital required. Pleasant work. Home every night. Make up to $12 a day. Wonderful new proposition. Particulars Free. Write McNess Co., Dent. 136. Freeport. Illinois. WANTED—Men to represent large shoe company. Good pay every day. No experience needed. Cem: leze sales outfit sent free. Write Consolidated Shoe System, Dept. $27, Chippewa Falls, Wisconsin. MALE & FEMALE HELP WANTED M. M. EARNED $267 raising mushrooms in ce: tional, but your çellar, suitable. We buy crops. United, 3848 Lincoln Ave., Chicago. MIDGET AUTOMOBILES BUILD a Midget Miller Racer. plete plans for constructing tic midget automobile appear i = 1938 edition of How-To- Build-It along with many other interesting heme and workshop plans. Send 50c fer page book to Modern Mecha: o.. Greenwich, Conn. MIDGETS! Motors! new; sport, racing. 80 motors, $4. 00 up. est Li Shipps Midgets, Box 543-B, Za Ohio. MISCELLANEOUS MARK your Tools with a Stecl Hand Stamp. Any Three Initials 75 Cents. Gideon A. Pike, North Attleboro, Mass. BURIED TREASURE, Minerals, free booklet, photographs. Fisher, Palmer Bldg.. Hollywood. AUTHENTIC information, any sub- ject, 50c. Paramount Press Service, Atlanta, Mo. When Answering Advertisements Please Mention May Modern Mechanix | SEND 10c for 1936 Handbook of In- ' : son; accessories, tires, batteries, Indian, . : SEND 15e for illustrated used Motor- ; ; many MODEL ENGINES LOCOMOTIVES Electric, Gas Engines, Castings, supplies. 25c. Latest Catalogue, usual refund. EMCO., 2417 North Ashland, Chicago. MODEL RAILROADING MODEL Railroad Supplies “O” Gauge (34" scale—1!i” between rails) Freignt Car Body Kits $1.00, Illus- trated Catalog 10c, Westbrook Co., Hasbrouck Heights, New Jersey. MODELS & MODEL SUPPLIES YOUR Ideas developed into practical working model. 30 years successful ` experience; thousands satisfied custom- i ers. Confidential service guaranteed. Bank references. Send 3c postage for 32 page book “Making Inventions Pay.’ Crescent Tool Company, Dept. T. Cin- cinnati, Ohio. ENGINE Catalog 20c, Particulars free. ; Evraymesco, 28 N. Clinton, Chicago. MONEY MAKING OPPORTUNITIES “SPARETIME Roads To Riches,” ex- plains hundreds new easy moneymaking opportunities, 10c. Lewis Co., 828-F Carpenter, Oak Park, Illinois. HOMEWORK Opportunities Magazine -—10ce. Sample—5c. Schumacher, 3503 Hirsch, Chicago. SEMIYEARLY forty pages 10c. 6x9. Home Industries, (D89) Benson, Nebr. MOTION PICTURE & SOUND EQUIPMENT ‘ LEARN Motion Picture Theatre Busi- ness. Home-Study Training: Manage- ment, Advertising, Projection. Free Catalog. Give Age. Theatre Institute, 345 Washineton, Elmira, N. Y. MOTORCYCLES & SUPPLIES RECONDITIONED Motorcycles. New --used parts for all makes. Authorized Harley-Davidson Dealer. Whitman Motorevcle & Supply Co., 405-9 South- west Blvd., Kansas City, Mo. Steam, fermation listing new and used parts, for Indian, Harley, Excelsior, Hender- 422 East Grand, Des Moines, Iowa. eycle catalog. Bargains. Largest stock genuine Indian parts and_motorcycles. Indian Motorcycle Sales, Kansas City, Mo. OFFICE EQUIPMENT TYPEWRITERS, multigraphs, address- ing machines, adders, dictaphones, dup- ; licators, sealers, folders. Save half, ; write Pruitt, 553 Pruitt Bldg., Chicago, OLD MONEY WANTED COMMEMORATIVE Half Dollars, Lincoln, Stone Mountain, Oregon, | Texas, Cleveland, Kentucky, San Diego, Long Island, g1.50 each. Illustrated | Catalogue No. 14, 25e. Norman Shultz, Salt Lake. Utah. OUTBOARD MOTORS ELECTRIC outboard from old automo- bile generator. Operates with car bat- tery. Smooth—quick. Easy to build plans 10c. LeJay, Manufacturing, 514 Lelay Building, Minneanolis, Minn. PATENT ATTORNEYS PATENT Your Idea. Write imme- diately for two free books, ‘Patent Protection” and ‘‘When and How to Sell an Invention.” Fully explain interesting points to inventors and illustrate important mechanical principles. With books we also send “Evidence of Tnvention” form. Prompt service, reasonable fees, thirty-nine years’ experience. Avoid risk of delay. Address: Victor J. Evans & Registered Patent Attorneys, tor Building, Washington, D. C. | The cost of this search is small, Scale Shows Postage Needed for Package A newly developed parcel post scale (above) can be used to weigh any package up to 70 pounds in weight. In addition, the scale has a calibrated aluminum chart fitted into it in such a manner that as the weight of the pack« age is recorded, the correct figures for postage required to mail the package to various zones is shown. PATENTS—DBefore too heavy an out- lay of time or money is made on an invention, a search of the Patent Office records should he made to determine as nearly as possible whether or not the same idea has been patented before. i while the value of the facts it uncovers is often considerable. We offer inventors ’ and manufacturers a thorough, prompt, confidential search service—plus ex- perienced counscl and assistance in every phase of Patent and Trade-Mark practice. Write for our new free hock containing valuable information relating to patent procedure. Clarence A. O'Brien and Hyman Berman, Regis- tered Patent Attorneys, 28-Y Adams Bldg., Washington, D. C. “INVENTOR'S Guidebook” containing 96 mechanical movements and advice about patenting, selling inventions, also “Record of Invention”, Free. Frank A. Ledermann, Patent Attorney-Engineer, 154 Nassau Street, New York. FINER Finishing. Rolls developed and printed, with One Colcred enlargément, or two professional enlargements. All for 25c (coin). Genuine, Nationally Known, Moentone Superior Quality. Moen Photo Service. a Crosse. Wis. UNPATENTED Ideas can be sold, I tell vou how anc help you makc the sale. Particulars, with list of manufacturers and wanted inventions, sent free on re- quest. Write Wilson Holmes, 995 Barrister Bldg., Washington, D., C. HAVE YOU a sound, practical inven- tion for sale, patented or unpatented? Tf so, write Chartered Institute of American Inventors, Dept. 5-A, Wash- ineton, D. C. PATENTS. Booklet free. Highest references. Dest results. Reasonable fees, Watson E. Coleman, Victor Build. ing, Washington, D. C. PATENTS Fat- INVENTIONS Commercialized, ented or unpatentrd. Write Adam Fisher Co., 582 Enright, St. Louis, Mo. pin a a PERSONAL STUTTERING and Stammering cor- rected at home. Booklet free. Paul J. Wolfe, Box 52, Pittsburgh, Penna. STAMMERING, Stuttering, for relief write E. H. Tarhox, 109 Penna. Ave., Binghamton, N. Y. 139

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Thermometer Boasts Dial-Type Scale a A new type of laboratory thermometer, provided with a dial-and-pointer scale encased in stainless steel and mounted atop an eight-inch stainless steel stem, has been developed by a well known manufacturer in Newark, N. J. The unit is said to be the first dial-type thermometer with an all-metal tem- perature element sufficiently accurate for scientific use, accuracy of 1% of 1% over the entire scale being guar- anteed by the manufacturer. PHOTO DEVELOPING DEVELOP and print your own pic- tures. Save time, money with our com- plete outfit, $1.95 plus postage, ar sent C.O.D. Includes electric ruby lamp, printing frame, photo paper, chemicals and equipment. One of hundreds of amazing bargains in our free, newest, money-saving bargain book. Send for it today! Central Camera Co., 230 So. Wabash, Dept. 15-J, Chicago. ROLLS DEVELOPED—25c coin. Two 5x7 Double Weight Professional Enlargements, 8 gloss prints, Club Photo Service, LaCrosse. Wis. AMAZINGLY Beautiful, Roll De- veloped, 8 Natural Color Prints, 25c. Reprints, 3c. Natural Color Photo, D-39, Tanesville, Wis. SENSATIONAL Offer. largements 25c. mit, N. J. PRINTING, GUMMED LABELS PRINT your own cards, stationery, circulars, advertising. Save money. Easy rules furnished. Print for others, big profits. Junior outfit, $9.00; job presses, $11 up. Details free. Kelsey Presses, B-57, Meriden, Conn. 125 LETTERHEADS 8x11 and 125 Envelopes—$1.00 postnaid. Benneville, 907 West Roosevelt, Philadelphia. 500 Yvetterheads and 500 Envelopes, $3.25 cash. Barry, Babylon, New York. 1.000 1x2 GUMMED Lahels, 4 lines, 50c. Paramount Press, Atlanta, Mo. PROPELLERS PROPELLERS Sled-Airplane, Lowest Prices, Catalog 10c. Woodcraft Pro- pellers, Hillside Station, Wichita, Kans. 140 Five 5x7 en- Cardinal Photo, Sum- “RADIO & TELEGRAPHY RADIO BUILDERS’ MANUAL—A book of radio set building plans and kinks for the home experimenter. Everything from a crystal set to a powerful 6-tube auto radio is included. Price 50 cents—order directly from Modern Mechanix Publishing Co., Fawcett Bldg., Greenwich, Conn. RADIO Engineering, broadcasting, aviation and police radio, Servicing, Marine and Morse Telegraphy taught thoroughly. All expenses low. Catalog free. Dodge’s Institute, King St., Val- paraiso, Ind. RADIOS PLANS 18 Distance Crystal Sets— SW record 4,250 miles, with ‘‘Radio- builder” year—25c. Laboratories, 7700-K East 14th, Oakland, Calif. “SHORT Wave” Crystal Set! Illus- trated plans 10c. Unicraft, 4932 N. Eighth, Philadelphia. : RAZOR BLADES 100 FINEST Quality, blue steel razor blades. Single edge $1.25. Double edge $1.00. ‘Ashton Mdse. Mart, 63 Basswood, Lawrence, Mass. SALESMEN WANTED MEN Wanted for Rawleigh Routes of 800 families. Sales way up this year. Reliable hustler should start earning $30 weekly and increase rapidly. Write today. Rawleigh’s, Dept. E-S-MOM, Freeport, Ill. BIG commissions selling stores celluloid pricing tickets, metal shelf moulding, menu covers, signs, chrome changeable letters. T. Pricing Press, 12+ White St.. New York. FULL size, visible total Adding Ma- chine, only $9.95. Unlimited market. Big commissions. Addomatic, Dept. B-13. 430 N. Oakley, Chicago, Illinois. ATLAS Window Sign letters. Large Sizes, Penny Each. Beautiful Free Samples. Atlas, 7941-G Halsted, Chicago. SPECTROSCOPES SOLAR Spectroscone $1. Chemical and ore spectroscope $2.50. Spectrometer $5. Cudding Sons, Campbell. California. TELESCOPES, MICROSCOPES, ETC. EXPERIMENTERS—Assortment 18 unmounted lenses. Suitalle—telescopes, microscopes, etc. $1.00 postpaid. Optical Works. Milton. Pa. TELESCOPES, Microscopes, Binocu- lars; 1938 bargain catalog free. Brown- scope Company, 5 West 27th Street, New York, TELESCOPES, Microscopes, Binocu- lars. Lowest Prices. Free Catalog. The Habby Man, Jefferson, Iowa. TELESCOPES, Microscopes, lars, Mineralogy, Chemistry. free, Teeko, Evanston, Illinois. Binocu- Catalog Portable Photographic Machine Operates in Ordinary Light A newly developed portable photo- copying machine with a fixed focus makes facsimile copies, similar to pho- tostats, of letters and records and can be operated in ordinary office light. VIOLET RAY LAMP ULTRA Violet-Infra Red. Dual Ray Health Lamp. Two separate untts in one. Promotes Sun Tan—Vitamin ED” Automatic control. _ AC-DC current, $3.90 postpaid, Detaiis Free. Beyer Mfg. Co„ 4515-M Cottage Grove, Chicago, WELDING IOME-MADE Arc-welder from North- East (Dodge) 12 volt automobile gener- ators. Requires field coil and brush changes for 40 volts D.C. Remote Con- trol 25-125 amperes, Dual 25-200. New method designed for beginners, actual welding views, real facts, over 3,000 instructive words. Certified Plans $1.00, C.O.D. $1.12, Airmail 12c extra. Welders Club of America, BB-3432 M-Mart, Chicago. Special: Limited quantity, Dodge 12 volt used generators with Certified Plans $5.00 F.O.B. Chi- cago. Special: Send ad with above orders for extra plans. “How to build Dodge Arc-Welder without rewinding.” ATTENTION! $1.06 brings big laboratory tested collection of over 100 of the most practical conversion plans. Arc-welders from electric auto motors, light-plants, hattery-chargers, Dodge generators, D.C. Power motors and generators. Fifty car generator con- versions make wind light plants. wind chargers, A.C. and D.C. generators, motors. Old transformers make A.C. a\rc-welders, spot-welders. Many others. All in one book. Practical Methods, Box 165, St. Paul, Minn. ARC-WELDING Outfit $1.25. Weld fenders, braze, solder. Lavrow, 4368-W, Warren, Detroit. Stamp appreciated. WIND ELECTRIC PLANTS BUILD Redecting telescopes; catalog free. Instructions 10c. Optical Labo- ratories. Larchmont. N. Y. BUILD astronomical telescope. Lens kit with mirror and instructions, $1.98. Chas. Koch, DeBeaue, Colo. FREE Instructions. Build Powerful Telescope. Low Cost. Atemsco, Box 213M, Flushing, N. Y. VENTRILOQUISM LEARN Ventriloquism by mail; small cost, 3c stamp brings particulars. Geo. W., Smith, 125 North Jefferson, Room $694, Peoria, Ill. BUILD wind light plant. We show you how. Complete plans and valuable catalog 10c. Wind plant parts, welders, electric fences. LeJay Mfg., 614 LeJay Bldg.. Minneapolis, Minn. FREE Electricity from Wind. Build your own Windcharger. Cost 98c for material plus used car generator. Draw- ings—lInstructions 10c. Wesco, Min- neapolis, Minn. WIND DRIVEN PLANTS GENERATOR propellers, expertly de- signed, factory prices. Universal Air- craft. Fort Worth, Texas. Accept No Substitutes! Always Insist on the Advertised Brand!

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Cut Sections For Microscope [Continued from page 135] begun to harden and set around the edges of the well, insert the bud and orient so that it lies either straight across or straight up and down. It may be necessary to hold it in place with warmed forceps until the paraffin has hardened sufficiently to prevent any change in position. When completely cold and hardened, the paraffin mass is ready to cut. This brings up for consideration the last but an important point—the plane of section. Or- ganic structures are built around certain planes of symmetry and the microscopist should know the terms employed. The higher animals, such as a cat or fish or man show bilateral symmetry or two-sided relationship of parts, the left half of the body being a mirror image of the right. One plane passes lengthwise through the body from head to tail and bisects the back and belly surfaces; a section in this plane is termed sagittal. Another passes lengthwise at right angles to the sagittal, bisecting the right and left sides; this is a horizontal or frontal section. A third is at right angles to both of these, passing across the body, and such a cut is a transverse or cross sec- tion. The first two are both longisections, as opposed to the third. In objects not bilateral, but built with the parts radiating from a common center, as in a starfish or a tree trunk, the symmetry is radial and the planes receive different names, A radial section is any longitudinal one that forms a ra- dius, while a tangential cut is longitudinal and parallel with a radial, but forms a tangent and not a radius of the circle, lying off-center. The third plane is transverse or cross, as before. In none of these cases do the planes pass ob- liquely, and the operator must use care never to make oblique sections, but only those parallel to one of the planes of symmetry. Oblique sections are confusing and do not give a picture of in- ternal organization that can be interpreted easily. The best practice is to gain a knowledge of [Continued on next page] ta ADDING INTEREST TO STAMP COLLECTING _ Oli if z Winter : Piumpifh ) 393 Garmi When the Austrian government issued the stamp shown on the left they never expected it to be sought by collectors everywhere. When issued it was found that the ears were reversed on the man. The corrected stamp appears at right. Iu order to properly advertise the Winter Olympics at Garmisch-Partenkirchen, the German government supplied the post office at Stuttgart with a special postmark depicting a skier and the Five Ring Olympic symbol as shown above. ADLETS FOR HOBBYISTS (See regular classtfled section for rates and other Informatlon.) STAMPS SUPER-WONDER Packet o7 stamps from Afghanistan. Manchukuo, Sudan, Guadelou British Colonies, including na entire packet for only 5 c approval applicants. Big illustrated lists free. Kent S:amp Company, Box 87-2 (G.P.0.), Brooklyn, N. Y. 1897 GRAND Comore Islands. Turks Caicos, $5 U. S., British C Samoa, ete, Everything 3c with Hanson Place, Brooklyn, N. Y. FANTASTIC Indochina, Somaliccast German State, Perak, Selangor, Sembilan, Bicolored Banana Airmail, Siberia— Free with Approvals! Postage 3c. Saxon Company, 3 Dekalb Ave., Brooklyn, N. Y DIAMOND Airpost Commemorative Issue Complete, Pro- letariat Portraits Complete, Dragon Stamp, with 117 addi- tional, cataloging $3.00, only 10c. Friendly Filatelists, Box 4428M, Philadelphia, Penna. NEW Rivera nude stamp! World’s largest triangle! Congo, Sudan, South Seas, bicolors, pictorials and many others. Only 3c with approvals. Cactus Junior Approvals, Box 1870-D, Tucson, Arizona, . containing 60 different nsjordania, North Borneo, raq, Sarawak, French and és, beasts, ships, etc. This e old genuine Baden, Map Stamp, Western rovals. Viking, 1-MM STAMPS! Illustrated Album 100 diff. 3c; 500 diff. 35c; (4000 spaces) 22c. Tatham Stamp Co. (D9) Springfield, Mass. BRITISH Colonies. 54 Different including Jubilees and Coronations 10c with approvals. Swedell, 3129 Garfield Ave., Minneapolis, Minn. UNITED STATES—45_ Different, Perforation Hinges, Bargain Price List—all for 10c. Baroda, Mich. MIDGET MIXTURE—100 foreign stamps—Asia, Malta, Europe, etc., 5c. Guy Elsea, Bowling Green, Ohio. FREE!!! Two Coronation Sets. Postage 3c. 312T Shearerbldg, Baycity, Michigan. COINS FREE: Foreign Coin, Banknote and Large Illustrated coin catalogue, for 4c postage. Approvals sent. ‘Tatham Coinco, Springfield-9, Mass. INDIAN CURIOS INDIAN CURIOS. 100 good ancient Arrowheads_$3.00. Tomahawk Head 50c. Illustrated catalog Sc. H. Daniel, Hot Springs, Arkansas. 1,000 diff. 90c! Approvals sent. _ Gauge, Seidenberg, Roberts, When Answering Advertisements Please Mention May Modern Mechanix 441

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CAMERA FANS— YOU ASKED FOR THIS BOOK! 300 PICTURES 144 PAGES For months readers of MODERN MECHANIX have been asking us: "Why don't you put out a complete photo manual of some kind that tells in non-technical language how to develop, print and enlarge our films, how to make our own darkroom equipment, how to improve our cameras, how to make good pictures?" The new PHO- TOGRAPHY HANDBOOK is that book! Al- though it has been on sale only a few weeks, it has already been acclaimed far and wide as one of the most useful and practical books on the market. No matter what kind of a camera you own—$1.00 box brownie or a $200 miniature —you will want a copy right away. On sale at newsstands, or obtainable directly from us, postpaid. Fill out the coupon below: FAWCETT PUBLICATIONS, INC., Fawcett Building, Greenwich, Conn. Enclosed find fifty cents. Please rush my copy of the new PHOTOGRAPHY HANDBOOK. Address [j (Remit by money order or check. Do not send coins i through the mails.) t t a p-=r=nennn nenm mam i 142 A Utility Table For The Auto [Continued from page 128] On the same end of the post but on the opposite face is screwed the long tab of a T hinge and the two sections of the table are now ready for as- sembling. To do this, hook the table top into the dash compartment and place the supporting post under it, moving it toward the rear of the car until it just misses hitting the front edge of the seat. Make sure the post is square and true with the table and mark the hinge holes for the screws. Now take the table out of the car and screw the leg to the under side of the top, being careful that the leg folds away from you when the table is in use. To attach the table, elevate the front edge, push the back edge into the compartment, hook the two brass clips in the lip of the dash, pull toward you and lower the table to writing position. The leg will automatically swing into its proper place. As may be noticed in the detail drawing of the method of hooking the table to the dash, once the table is in position, the brass clips prevent it from sliding forward or tipping up at the rear, while the 12” square wood strip prevents the table from sliding too far into the compartment. Thus the table is firmly held at that point. The table may be left in position while you get in and out of the seat. Just lift up on the table slightly, to free the leg of weight, push the leg forward, slide your own leg by the table and re- turn the table support to a vertical position. It is thus not necessary to disturb a typewriter or anything else that may be on the table if one must get in or out of the car. Cut Sections For Microscope [Continued from page 141] structure by inspecting first a cross and then a longitudinal section, and most microscopists make both and mount one of each under the same cover glass. In the case of tree buds this would be a recom- mended procedure. Cut true cross sections near the middle, then cut true radial sections and mount one of the best of each on a single slide, side-by-side. Never mix unrelated subjects on the same slide, however. Next month we are going to delve into the mysteries of preparing such materials as plant and animal sections for permanent preservation, but meanwhile, so that you can see what some of your efforts look like under the microscope, stain a few of your best sections in dilute mer- curochrome, place in strong alcohol for over- night, then into xyol or carbol-xylol for an hour and mount in balsam. These are not the per- fectly finished slides we have promised you, but are merely to serve until the next step in technique can be explained. And here’s wishing you good cutting! Accept No Substitutes! Always Insist on the Advertised Brand!

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Coal Shows Heat Content A new experimental method by which scien- tists can look at a piece of coal and tell how much heat it will generate was announced at the meet- ing of the American Institute of Mining and Metallurgical Engineers. Two midwestern geologists, L. C. McCabe of the Illinois Geological Survey, and Prof. T. T. Quirke of the University of Illinois, described the secrets of coal analysis in their technical paper, “Angle of Polarization as an Index of Coal Rank.” Tiny cubes of coal are polished and brightly illuminated with a small lamp. The light reflected from the polished surface becomes polarized and is studied with Nicol prisms to determine the angle of polarization. By a fundamental rule of optics known as Brewster’s Law, the angle of polarization of the reflected light can be related to what scientists call the index refraction. This last is the degree of bending which a material will cause as light passes through it. Final and significant step in the research was the discovery that the amount of heat in B. T. U. (British Thermal Units) which a unit amount of coal can produce is related by a simple straight- line relationship with its index of refraction as measured in the apparatus. Using the wide range of different kinds of coal found in Illinois from woody lignite to soft bitumi- nous and so on to harder bituminous it was found that as the heating qualities of the coals increased, so too, did their index of refraction. The method, pointed out Mr. McCabe and Prof. Quirke, is still in the experimental stage and the accuracy of the technique could be increased ten or one hundred times with better equipment. “This investigation,” they declared, however, “with «improvised equipment imperfect in many particulars, has discovered what appears to be a physical criterion for rank identification (of coal) .” Desert Produces Gas For Ice INED like petroleum in shallow wells, carbon dioxide gas is being converted into dry ice at two plants near the shore of the Salton Sea in the Imperial Valley of Southern California. The carbon dioxide was discovered several years ago when a power company drilled for dry steam. Later two engineers, W. P. Morse and Carl W. Einhart, investigated the possi- bilities of converting the gas into ice at low cost. Today 12 tons of the refrigerant are being produced daily. Wells 650 feet deep tap gas, which then is pumped four and a half miles to a compressing plant. After temperature is reduced it is fed in the form of snow, into giant presses. AUDELS Carpenters and Builders Guides 4vols.$6 Inside Trade Information for Carpenters, Builders, Jein- ers, Building Mechanics and all Woodworkers, These Guides give you the short-cut instructions that you want— including new methods, idens, eolutions, plans, systema and moncy saving suggestions. An easy progressive course for tha apprentice and student, A Practical daily helper and Quick Reference for the maater worker, Carpenters every- where nre using these Guida as a Helping Hund to E Work, Better Work and ter Pay, To get this pit ance is goreh ott simply i Blt in and mai e inside Trade Information On: PON below. How to usa the steel squarc—Tlow to file and set saws—How_to build furniture—IIow to use @ mitre box—How to use the chalk line—Ilow to use rules and seales—Ilow to make joints—Carpentera arithmetic—Solving mensuration problems—Es- timaling strength of timbers—Ilow to set girders and silla—How to frame houses and roofs—How to estimate costs—How to build houses, barns, gar- ages, bungalows, etc.—How to read and draw plans—Drawing up specifications—How_to ex- cavate—How to use settings 12, 13 and 17 on the steel aquare—How to build hoists and scaffolds— sxylights—How to build stairs—How to put on interior trim—How to hang doors—Low to lath— lay floors—Tlow to paint SRE REESE THEO. AUDEL & CO., 49 W. 23rd St., New York City Mail Audels Carpenters and Bulders Guides, 4 vals., on 7 daya’ free trial. Tf 0.Ks Twill remit $1 in 7 days, and $1 monthly until $6 is paid. Otherwise I will return thera” N% obligation unless I aim satisfied. Relerence. .. New Catalog of TRAILER PARTS f New catalog of trailer parts at bargain prices. Axles, straight, $4. Drop center axle, $7.50. Drop center axle undercarriage, $19.50, complete less Lires, Cable-controlled brakes on axle, $15 extra, Electric brakes—prices on request. Send for FREE Catalog today, Shamrock Traller Parts, 12319 Turner, Detrolt, Mich | PATENTS More than 62 years’ successful ex-.-] perience securing, good Patents for © Write for FREE booklets: ' explaining Patent procedure, selling inven tors. inventions, etc. C.A.SNOW & CO. Dept. C Snow Building WASHINGTON, D. C. When Answering Advertisements Please Mention May Modern Mechanix 143

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o- 418-YA, 9'4" swing Herizontal Motor Briven Pete eo ounters Motar, Switch 3 aft Belts: ve Daw. Toe Month SOUTH, BEND BACK-GEARED SCREW-CUTTING PRECISION LATHE $ fF 00 This 9-inch South | = Bend Lathe¿used-by: MANUFACTURERS TOOL ROOMS Less Motor Drive: LABORATORIES Sold on Easy MACHINE SHOPS - Payments as —Automotive Low as $6.00 a Electrical Month for 12 ` Gun Smiths to18 Months: U.S. GOVERNMENT SCHOOLS- HOME WORK SHOPS INVENTORS + The9”x3' South Bend Precision. Lathe does these operations: TURNS—BORES h. ee x $117. 00 Pantene p- Reversing 3 for 4g Months} IRON AND OTHER METALS. INVALUABLE TO INDUSTRIES E FT 9”, 11",.137, 15” and EVERYWHERE FOR HANDLING E motor or counter- =| PRECISION OPERATIONS... ERa zs ows. industries everywhere are using the 9-inch Workshop South Bend Lathe—and finding it the most profitable invest- ment they can make. Designed and constructed for precision accuracy, this 9-inch Lathe handles machining operations to the most exacting specifi- cations. Workmanship and new features insure speed, accuracy, and versatility. Industry finds it cannot afford io overlook this remarkable tool. Features include—Twin Gear Reverse to Lead Screw, Ball Thrust Bearing on Spindle, Auto- matic Longitudinal Screw Feed to Carriage, Pre- cision Lead Screw for cutting screw threads from 4 to 112 per inch, 34-inch hole through spindle taking collets up to 14-inch, V-ways on lathe bed. Screw Threads,” 10c, E ONo.35, “How to Grind H O No. 46, ‘*9- inch, Work- Address.. shop Catalog,” Free, E a EEEE OEE = esse aneeine SOUTH BEND Øzecision LATHES WRITE FOR Laila BOOKS Emmet EEE E] i ] O No. 33LB, “How to SOUTH BEND Ao WORKS, Run a Lathe,” 25c, 267 E. Madison St. South Bend, Ind., U.S.A. O No. 36A, “How to Cut Please send the books checked hers. Class of Work.......cceeeeeee Cutter Bits,” 10c, Name....... SiStats snd PEA 38 attachments are available for milling, grind- ing, draw-in collet chuck work, taper work, and many other operations. Made in 3’, 314’, 4’, and 414! bed lengths. Costs less than 2 cents per hour operating from ordinary lamp socket. SOUTH BEND LATHE WORKS 267 East Madison St., South Bend, Indiana, U.S.A, LATHES AKE STOCKED IN PRINCIPAL CITIES Chicago, Ill.—C. B. Burns Mchry. Co., 541 W. Wash. Blvd. New York, N. ¥.—A. C. Colby Mchry. Co., 183 Centre St, Philadelphia, Pa.—W. B. Rapp Mchry., 132 No. Third St. Los Angeles, Cal.—Eccles & Davies Mchry., 1910 Santa Fe St, Detroit, Michigan—Lee Mchry. Co., 6318 E. Jefferson Ave. Milwaukee, Wisconsin—Voell Mchry. Co., 1533 No. 16th St. Boston, Mass.—The MacKenzie Mchry. Co., 36 Oliver St. Cleveland, Ohio—Reynolds Mchry. Co., 2034 E. 22nd St ES i i ae 144 Accept No Substitutes! Always Insist on the Advertised Brand!

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Cotton Used As Roadbinder Down in Alabama recently dusky cotton pickers, pulling long cotton sacks bulging with the fleecy staple, paused long enough at the end of their rows to watch highway construction nearby. Their attention was attracted by the laying of a canvas-like material between the layers of sand, slag, and asphalt. The Negro farm hands didn’t know it, but the same substance they were picking, except in different form, was being used to build up the road. No one took the trouble to tell them, but they were seeing history in the making. Now traffic is moving over this first “cotton high- way,” a small part of an extended program being fostered by the U. S. Department of Agriculture in which some 6,167,000 square yards of cotton fabric are being provided for the building of over 500 miles of roads in 24 states. Advocates of “cotton paving” contend that it not only reinforces the bituminous surfacing of the highway, but also prevents it from cracking and improves its resistance to water. In a broader sense it is hoped that a great new domestic market will be provided for the chief product of the southern farm. But the cotton fabric must prove its case before being widely used in highway construction. Six bales of cotton per mile are required for the usual “farm to market” highway and its use increases construction costs about $1,000 per mile. A year or more will be required for an adequate test of the new highway. The rolls of cotton fabric as they come from the mill are 82 inches wide, three rolls being re- quired after allowing for lapping to cover 20 feet of the usual 22-foot roadway. It is laid on a coating of hot tar, then more tar applied, with other layers of slag and asphalt coming on top. Alabama proposes to build 119 miles of cotton fabric highways, using 1,260.094 square yards of the material, or more than any other state. North Carolina comes next with plans for 105 miles. Twenty-two other states will use varying amounts. Naval Observatory Builds More Time-Signal Clocks Two automatic crystal-controlled clocks are being built by the U. S. Naval Observatory in Washington, D. C., for addition to its time-signal broadcasting service, Capt. J. F. Hellweg, Super- intendent of the Observatory. reports in his synopsis of work for the fiscal year 1937. Used to send out at frequent intervals time signals for mariners and scientists who find them indispensable, the clocks, which are regulated by a vibrating crystal, are intended for the naval stations at Mare Island, Calif, and Honolulu. Twenty time signals are sent each day from the naval radio station at Arlington, Va., and five are broadcast from Mare Island. When Answering Advertisements Please Mention May Modern Mechanix laa at Home to Make $30, 50, °75 a WEEK Chief Operator Broad- casting Station ‘When I completed 20 lessons, I ob- ast Opera- tor’s license Gnd immedi- ately joined Station WMPC, where I am now Chief Operate HOLLIS HAYES Madison Ši., Lapeer, Mich. Own Business “I now have my own Radio business which shows three hundred dollars a month _ profit— thanks, , again to ptlonal Radlo FRANK hater. 39 N. Felton st, , Philadelphia, Penna. pry Earned $50 First Month in_Spare 1T knew Radilo. four I began ser- Radios, earning $50 rst month. Last win- made as high as $100, ia month in are F. W FALA ON, f: Qlney Road, Norfolk, Va. Mail this Now FREE Dept. BEH, National Radio Institute, Washington, D. C. Dear Mr. men at a I i I i] Li i explalns Ù Radio Experts. } |: q i a 4 J. E. SMITH, President, Smith: Without obligating me, send “Rich Rewards in Radio,” which polnts out the spare time and full time opportunitles in Radio and your 50-50 method of home in spare (Please Write Plainly.) Do you want to make more money? Broads casting stations employ engineers, opera» tors, station managers and pay up to 5,000 a year. Spare time Radilo set servicing pays as much as $200 to $500 a year—full time servicing jobs pay as much as $30. $50, $75 a week. Many Radio Experts operate their own full or art time Radio businesses, Radio manu- acturers and jobbers employ testers, in- Spectors, arenes en Ineers, servicemen, paying pa” to 86,0 a year. Radio operators Pn ships get Osod Y pay and see the world, Automobile, police, aviation, commercial Radio. and Ioud speaker sys- tems offer many good opportunities. Tele- vision promises many good jobs _soon. Men I trained have good jobs in Radio. Many Make $5, $10, $15 a Week Extra in Spare Time While Learning The day you enroll I start sending you Extra oney Joh Sheets. They show you pow to do dio repair jobs, how to cash guickly. Throughout your training I Feri Plans and ideas that made good spare time money for hundreds of fellows. T send speclal Radio equipment which gives you practical experlence—shows how to conduct experiments, build circuits Ilus- trating important Radio principles. Find Out What Radio Offers Mail coupon for “Rich Rewards in Radio.’" It's free to any fellow over 16 years old. Tt points out Radio's spare and full time opportunities, also those coming in Teles vision: tells about my Training in Radio and Television; shows you letters from men I trained. telling what they are do- Ing. earning: shows my Money Back Agreement, MAIL COUPON NOW in an envelope or paste on penny postcard. J. E. SMITH, President Dept. 8EH National Radio Institute Washington, D., C. RICH REWARDS IN RADIO training time to become AGE.....

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{ow eas for Homes Shop: Names and addresses of manufacturers of products described below will be sent free to any reader on request. l Compressed air for operation of a paint sprayer is created by this foot operated pump. The air is stored in a small tank and released through a regulator valve at a constant pressure. A wrist watch that not only keeps time but supplies the user with a stop watch, a tacho- meter and a telemeter. A handy drawing instrument for ruling lines and lettering. An clectric flare designed to provide a power- erful red beam from any angle. Even though knocked over in the road, because its lens has no dark zone, it can be seen easily. It will give either a steady or intermittent glare. It is water and dust proof. A pipe using a dehydration tube to eliminate excessive con- densation. Without the use of an absorbant cartridge, 97 per cent of moisture is eliminated, keeping shank clean and dry. 146 As seven-inch incorporating principles of Four speeds, between shaper modern shaper construction. i forty-five and 200 strokes a minute are available. A rubber or friction tape holder to be worn on the belt. It allows the tape to be rolled off as needed. A special light for use when a car is on a lift and workmen are under it. Attached directly to the lift, it rides up or down as the car is raised or lowered. Reflector and bulb can be removed. without disturbing the wiring. A pressure oiler for delivering the exact amount of oil to the spot where it is re- quired. The amount of oil delivered on each stroke is regulated by an adjusting nut. A basket type of sink strainer. It can be opened or closed quickly and easily, and it can be emptied without the fingers touching the refuse. Two sizes are available for large and small sink openings. A one-piece asbestos suit for fire fighters. The shoes and the body of the garment are in one piece and it is put on with a zip- per fastener. The zipper is pro- tected by an asbestos flap, so that in the event the wearer is over- come, the suit can be removed quickly. A reversible hand guard which can be used with or without gloves. It is seven and a half A Eebe inches long, and is made of high ie PA ach quality chrome leather, steel square drive stitched to prevent ripping. tadh ments.

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: | fe wy when its me.. my pipe.. and VELVET” +A Copyright 1938, Liccerr & Myers ToBacco Co. eRINTER iN U.S.A

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With Independent Tobacco Experts.. WITH MEN WHO KNOW TOBACCO BEST — Nee. en ARE THE FACTS! Sworn records show that caa among independent tobacco experts, Lucky AL Strike has twice as many exclusive smokers as have all other cigarettes put together. These men are auctioneers, buyers and warehousemen. They deal with all, but are not connected with any manufacturer. They à 4 H ave You He ard know tobacco and they smoke Luckies... 2 to 1! = i ; a Remember, too, the throat protection of the exclu- Bat x the Chant ot the sive process, “It’s Toasted.” This process removes cer- tain harsh irritants present in all tobacco, and makes Lucky Strike a light smoeke—easy on your throat. Tobacco Auctioneer

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Alt. Cover

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U.S. "M Ag D F RN ARNOLD ra MI | SEE PAGE 72

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uble Page Spreads

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A frank man to man talk about PATENTS-INVENTIONS a INVENTIONS HE world of invention moves on. About a hundred years ago people were saying, “There’s nothing left to invent”—today we know that is one of the funniest things ever said. Just think what has happened in the last hundred years! Autos, radios, airplanes, and thousands of useful, practical devices for home, shop and office have been invented and put on the market. Inventors are con- stantly making the world a better place to live in. Did you see a notice in the paper that an obscure worker, Hans Wach, has invented a simple device to utilize exhaust steam on steam boats. Already, the report states, the steam ship lines have saved more than $15,000 in fuel bills with his invention. Almost in the same breath the Dept. of Commerce announces that it will soon test out a new non- crashable aeroplane, which the average man can learn to fly in a day, which will travel at 110 miles an hour and sell at the price of a cheap automobile. An unknown Seattle man has invented a robot to go 5,000 feet under the sea and recover millions and millions of dollars worth of gold lying at the Who Are Inventors? Youd be amazed at the men we con- Can You Answer These Questions? Ask yourself these questions: How do bottom of the ocean since the days of the early Spaniards, Remember this: For every outstanding big inven- tion there are thousands of small, simple things for use in the home, the office, the factory, on the farm, on every sort of travel conveyance. Little articles like you find on the counters of a 10-cent store, hardware store, drug store, toy and novelty shop. Many Little ideas Have Big Commercial Possibilities A person finds something he’s using doesn’t work right, or it’s clumsy, or costs too much. He gets a happy thought. He improves the old Article. That’s contribution to human progress. That’s the way that many, many men have reached the goal of financial comfort, independence and even wealth. Most of the things millions of us use didn’t come from the brains of engineers and physicists. They came from the mind and maybe the crude home work bench of Mr. Average Man, busily engaged in earning his bread and butter at whatever chance or circumstance has given him to do. The “little” man’s opportunity as an inventor was never greater than it is today. Our Business Is To Help You. Write Us Today 115 Mechanical Move- ments Like These Besides many other features and facts there are 115 differ- ent mechanical movements and principles in the big, 48-page Book below. Maybe there is just the idea you need to solve some mechanical problem. Use the coupon or write us a card or letter. FREE BOOKS with 68 PAGES of Facts and Pictures! tuet in the course of a busy year. Most of them do not consider themselves inventors at all. During their work or leisure they get an idea. They A work it out on paper. They get > in touch with us about Protection. Did you know that a dentist invented the stock ticker, a school teacher the telephone, a farmer the typewriter, an artist the telegraph? Did you know that the crinkly bair pin—sold by millions r 7 how shall I reach people who now—came about because a husband saw his can market my invention? Can I protect and wife twisting the old-fashioned straight hair sell an improvement on some invention that pin to make it stay in place? Poor men who has already been patented? These are but a have no thought of invention now will be few of the questiens which usually confront financially well-fixed in a few years because the average man, You need the answers! of a happy thought that the world could use YOU CAN HAVE THEM, without cost, to advantage. trouble, or delay. the Patent Laws protect me? What easy steps can I take, without cost, to put myself in position to support my belief that I am the first man to think of my invention? Is a Patent worth the cost? Do I need a model? Should I try to sell my invention before I have it Patented? Is there any safe, business-like way te secure financial help? If I do apply for a Patent For more than forty years, this firm has been helping men with an inventive turn of mind. We maintain a large staff of trained, experienced speclalists—Registered Patent Attorneys, Draftsmen, and Searchers to help our clients secure all the protection to which they are entitled. Fees are reasonable. De- ferred payments frequently arranged. Ques- lions promptly answered. Write us frankly with absolute assurance that what you say will be treated with strictest secrecy. But FIRST, send for the FREE BOOKS shown on the rg, posite nage. They are filled with facts, pic- tures and suggestions. They tell you things about Patents, Inventlons and Selling Inven- tions that we have learned in our long experience. They may save you time, expense, EVEN LATER DISAPPOINTMENT. Simply fill in the coupon. No charge, no obligation. Write us today. 6 Accept No Substitutes! Always Insist ou the Advertised Brand! NEW BOOK About Selling INVENTIONS So far as we know, the facts in this booklet have never before been pub- lished by any Patent At- torney. You are given very definite suggestions “When When g VICTOR C ; VAN 5 & Co. REGISTERED PATENT ATTORNEYS | MAIN OFFICE: 30-E, VICTOR BUILDING, WASHINGTON, D. C, Other Offices: 2610-B, Singer Bldg., New York i 1445-B; Monadnock Didg., Chicago 1010-B, Hobart Bldg 405-1, Garfield Bldg’, Los Angeles Send me FREE copies of your books, "Patent Protection’? and | San Francisco cn and How to Sell an Invention.” (Note: Same bosks sup- plicd by any of branch offices listed above.) City or Town g Advertisements Please Mention May Modern Mechanix Fd

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D Small Duveriliom THAT HAVE BUILT BIG BUSINESSES l AI VENTIONS do not have to be complicated to be profitable when Pat- ented. The 5c and 10c stores flourish on simple Patented products which are commercially suc- cessful. The zipper, safety pin, thumb tack, paper clip, collar button—all simple, yet familiar inven- tions—brought their inventors rich rewards. If you have a Patentable invention—act to prctect it. Many of the most useful, widely popular, greatly Cc) fo) É A a E>, profitable, and extremely successful inventions have been very simple ones, look at the devices we have pictured here to realize how a simple invention may become a utility bought by a hundred thousand or a million people soon after it is produced. Don’t be afraid that the simplicity of your invention makes it valueless. The thing that you find so simple that you wonder why a thousand other people haven't already done it is often the invention worthwhile. You have only to HOW OTHER INVENTORS GOT STARTED The list of men who succeeded in in- vention with only a poor boy’s start is f a very long and noble one. Poverty, hardships, lack of friends, distance from the market—these could not hold 4 back Bell, Edison, Eastman, McCor- ieg mick, Whitney and others. Everyone O e = cannot succeed. But every man can try. Courage, sacrifice, and hard work may bring you a measure of the success these men had. Lack of mechanical ability is not a serious drawback. You can always get someone able to build a model, draw a detailed design, cr otherwise materialize your invention $ for you. The big drawback is discour- agement. Your invention of a practical article or an improvement upon an old one should be patented NOW. Frequently many of the thousands of applications filed in the U. S. Patent Office each year are for the same or almost the same invention. In such a case, the burden of proof rests with the last ap- plication filed. Sometimes a delay of even a few days in filing the applica- tion means the total loss of the patent. LOSE NO TIME. The entire time of this large and ex- perienced organization is devoted ex- clusively to patent and trade-mark eases. We know the rules and require- ments of the Patent Office. We under- stand the technicalities of Patent Law. We can proceed in the quickest and safest ways in preparing an application for a patent covering your invention. Views of the man who used Patent Protection to amass millions and give per- FREE: -- BIOGRAPHY OF GEORGE EASTMAN fection to a new art—Photography—itself one of the greatest inventions. 317-C ADAMS BUILDING CLARENCE A.OBRIEN & HYMAN BERMAN WASHINGTON, D. C. Registered Patent Attorneys Before U. S. Patent Office 12 Accept No Substitutes! Always Insist on the Advertised Brand! If you have an invention that is patentable—and want to secure for yourself your inventor’s sole right to profit from the invention—you can’t afford to lose time in securing the protection of a U. S. Patent. Other inventors may be working on the same invention right now. Should they develop this invention and file patent application before you do—the burden of establishing priority will be upon you. Our Big Book—"Patent Guide for the Inventor”—will tell you the quickest possible way to secure SEND FOR IT TODAY! Patent Protection for your invention, The First Important Step in Securing a Patent is to obtain the services of a Regis- tered Patent Attorney. The U. S. Patent Office advises that you secure the aid of an experienced Registered Patent Attorney to prepare your statements. Establish the date of your invention as explained in our book and disclose your invention to him in correct form. He then makes a SEARCH of the Patent Office Records and reports to you on exist- ing U. S. Patents which might bear on your invention, giving his opinion on the advisability of proceeding and filing formal application. Reasonable Fees—Con- venient Terms Don’t worry about finances. Our fees are very reasonable—we can arrange convenient terms of pay- ment. It is our custom to permit clients to pay for our services in in- stallments as the application pro- gresses in our office. See our Big Book for fees in obtaining Patent. It explains our arrangements clearly. Send for it NOW! FREE RECORD OF INVENTION FORM Use our Free “Record of In- vention” form to assist you in recording the descriptive out- line of your invention and to establish the date of your in- vention, With it you can make a rough sketch of your invention and have it wit- nessed in a matter of value to you as evidence should occasion arise. CLARENCE A. OBRIEN and HYMAN BERMAN 1 7 H 317-C Adams Building, Washington, D. C. 4 , Registered Patent Attorneys 4 J Before U. S. Patent Office H 1 Please send me at once your Big Free 48-Page Book, “Patent # 1 Guide for the Inventor” and your Specially Prepared “Record of g f Invention” form. This request does not obligate me, i T Xati wen H E e E E T : 1 ‘ 1 r 1 L] (Please e or print plain [an mm m mm m m m m o an a m m m n a m a a s m a R a o a a e n a a a m e a pr When Answering Advertisements Please Mention May Modern Mechanix 13

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Chins kom the éditor's W “When good fellows get together’—a fleet of four “Little Bear” boats constructed from MM plans by Minnesota fans. PHOTOS of boats of all types and sizes from kyacks to sailboats as well as power boats fea- turing outboard, inboard and propeller-drive motors have flooded the Workbench this month, so in response to this expression of popular interest in home-built boats we are devoting the entire space to the subject. Norman Schauer, of St. Paul, Minn, was awarded first prize of $5, for his letter and photo describing a fleet of MM boats. The letter reads: Dear Editor: lam sending you a photo of four “Little Bear” boats constructed by George and Art Maguire, John Alden and myself, all of St. Paul. We thought you might be interested in the photo as the boats were built from plans in the MM book—"How To Build 20 Boats,” 1936 issue. We are organizing a boat club and will soon have ten “Little Bears.” Hoping for more plans for small boats in the future, I am, Norman Schauer. Good work, fellows. The club angle sounds like a good idea and the 1938 MM boat book ought to interest your entire group. Copies are available from our Greenwich, Conn., office at the usual price of 50c per copy. 28 A photo and letter describing a very novel water craft won a $3 award for Fred Pilates, of St. Louis, Mo. He says: Dear Editor: As a physical culture specialist and a constant reader of MM I developed the “‘aircycle," shown in the enclosed photo. It is constructed of bicycle paris, mounted on a surfboard which is balanced on pontoons. Total weight is 30 pounds, Fred Pilates. We have a strong hunch that reader Pilates will receive many inquiries from MM readers asking for construction details of his unusual craft. Mounting parts of a bicycle on a surfboard balanced by pon- toons, Fred Pilates constructed this novel “aircycle” boats Modern Mechanix An interesting letter from far away Australia won a $3 award for H. V. Kenna. He writes: Dear Editor: I am a very keen reader of MM, especially the Editor's Workbench, and feel that I am at last eligible to write to you as I have completed my version of “Whizzer,” the plans for which appeared in the MM boat book. The craft is powered by a motorcycle engine, fitted with a propeller of my own design and construction, and attains a speed of 20 m.p.h. H. V. Kenna. Inasmuch as reader Kenna is a licensed air- plane pilot, it was almost natural that “Whizzer” would tempt him as a construction project and he has certainly turned out a first class job. kok k Outboard fans will undoubtedly be interested in a letter and photo sent in by Warren Mathews, of Bound Brook, N. J., who also was awarded a $3 prize. He says: Driven by an airplane propeller fitted to a motorcycle engine mounted at rear, H. V, Kenna’s “Whizzer” travels 20 m.p.h. Dear Editor: The enclosed photo shows “Buzzer,” built to MM plans. It travels about 22 m. p. h., powered by a 25 horsepower outboard engine. My next project will be an inboard job, built to your plans. Warren Mathews. Your “Buzzer” rivals many commercial boats in its appearance, Mathews, and we compliment you on your craftsmanship. eR Ok Another Minnesota reader who was awarded a $3 prize this month is James W. Spoor, of Cloquet, whose letter reads: Dear Editor: I am enclosing photos of a round bottom boat of my own design. It handles well with a 16 horsepower out- board and one of the photos shows its stability. I enjoy MM every month, especially the construction Projects. Let’s have more boat plans, James W. Spoor. May, 1938 Warten Mathew’s “Buzzer” outboard motorboat not only looks well, but sails well, too, judging from the above photos. Spoor’s boat certainly reflects his excellent knowledge of boat construction. However, with good plans and a few simple tools, reader, you, too, can build a small boat that will insure many healthy and happy outdoor hours during the coming summer months, eR OF A letter and photo describing a home-built MM kyack won a $3 award for Bob Nissley, of New Brunswick, N. J. His letter states: [Continued on page 31] James W. Spoor’s home-built 15-foot round bottom boat is 5o stable that a man can stand on the gunwale (top) without capsizing it. Lewer photo shows construction details. . 29

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Chicago; KSD, St. Louis; WHO, Des Moines; WGH, Norfolk, Va.; WHK, Cleveland; KSTP, St. Paul; KMJ, Fresno, and KFPK, Sacra- mento. The facsimile recorder will be sold at a price no higher than the average good broad- cast receiver. When production is increased the price is expected to be reduced to that of the average medium priced midget receiver. With the exception of the recorder, no special equipment is required except the broadcast receiver itself. This new medium of entertainment and education is not to be confused with tele- vision, differing most widely from it in that its operation produces a tangible newspaper on which appears the printed word, photo- graphs, drawings, sketches and even adver- Inventor William G. H. Finch holding a newspaper printed by the recorder he developed. Below, right is shown the printing section of the Finch recorder. The arm swings back and forth across the paper in synchronism with the beam of light scanning the copy at the transmitter. While tele- vision remains -hiding around the mythical “corner,” fac- simile brings news, photo- graphs, sketches, and draw- ings into the home today. tisements. As the newspaper is produced, it can be removed from the machine and preserved if desired, differing from the con- ventional type only in size. Briefly, the operation of the transmitter and recorder is as follows: The copy to be transmitted—whether it is pictures, news flashes, line drawings or comic strips—in- volves no special printing or preparation because the material itself can be inserted directly into the transmitter. An electric bulb, throwing a spot of light, moves back and forth across the copy to be transmitted. This action is similar to that of the human eye' as it sweeps from left to right across a line of type. In its movement across the copy, the spot of light is reflected back into a light-sensitive photo~electric cell. When the scanning light strikes the white portions of the copy, it returns a full reflection to the light-sensitive cell. When it strikes a black area, no light is reflected, while for the shaded areas, a corresponding reflection is obtained. Because of the action of intermittent light at the cell, these reflections are changed into electrical energy or impulses. At the re- ceiver or recorder, these impulses operate a stylus sweeping in synchronism with the scanning light at the transmitter. Thus a “black” impulse will cause the stylus to make a black mark on the paper while a “white” impulse will not cause a mark. Radio facsimile service, as it is being considered by broadcasters, probably will supplement existing sound broadcast programs. It is planned that pictures and text will be broadcast on standard broadcast wave- lengths during the early morning hours, between mid- night and dawn, so that a complete bulletin will be ready for the user when he arises in the morning. A number of ultra-short wavelengths for day and night services also have been set aside. The FCC requires that each experimental station install a minimum of fifty receiver-printers for each facsimile scanner-transmitter. The experimental programs will determine, among other things, public reaction to facsimile broadcasting as a radio service, the best type of program material, and the technical requirements for both scanner and receiver. In use, the printer will be turned on automatically by a time clock in accordance with a pre-determined transmission schedule. In the same way, the printer is turned off in the morning when the facsimile trans- mission is completed. At this point, a really up-to- the-minute newspaper has been printed. Charles J. Young, RCA Victor engineer, with the facsimile receiver-printer he has developed for home use. Ordinary white or newsprint paper and carbon paper are utilized for reproduction. g =m Lees Army Here are examples of pictures and maps produced by the RCA facsimile re- corder. Although facsimile had been used experimentally by the army, it had never been adopted for regular use. In time of war, small portable receivers and recorders could supply maps to widely separated groups at the same time.

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the rapid progress being made Administration Communications Business Administration New York City Building Theme Centre—foundations ing for Perisphere & Trylon Mining and Metallurgy Consumers Medicine and Public Heaith Food—focal exhibit Fisheries Food Shelter—focal exhibit Textiles Stores—warehouse Utility—-operations Test Building (Photo by Fairchild Aerial Survey) Aerial view of the Central Exhibit Area, Flushing Meadow, N. Y., showing in the construction of exhibit buildings. 17. 18. 19. 20. 21. 22. 23. 24. 24A. Employment Office North Substation-—power Fire, Police, First-aid——Station 1 Field of Flags Fire, Police, First-aid——Station 2 Empire State Bridge—-over Horace Harding Boulevard Beginnings, Distribution Building Overpasses——Grand Central Parkway Extension, new level Temporary station, Long Island Rail- read Corner of Transportation Zone North end of Amusement Zone Court of States site Portion of Government Zone (Please turn to next page)

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PLANES and

by | Brigadier General - prit versaries, probable allies — war Designed primarily for attack À tactics against huge bombing plans. planes, the Bell “Airacuda” N A AA er febine spine. is There you have the constituent armed with six machine guns see it. First, for a statement of the measurements by which we compare air forces. Their effec- tiveness depends upon a number of constituent ingredients. These are: Airplanes: number, type, charac- teristics, accessory equipment. Operating crews: number, type, and state of training—pilots, gunners, bombers, navi- gators, radio men. Maintenance crews: number, state of train- ing of maintenance men, for servicing, repair and overhaul of planes and engines. Air bases: flying fields, shops, hangars, bar- racks, safe harbors for machines and men. The state of the aircraft industry: how May, 1938

variables—machines, men, bases, resources, missions — by 2 these yardsticks shall we judge Air Forces. We have more than one thousand modern fighting planes in our Army Air Corps, divided into the type categories, pursuit or fighters, bombers, attack, and reconnoissance and observation. These planes, type for type, are the equal of those found elsewhere in every case, and in several types we are distinctly superior to those pos- sessed in quantity by any of the other lead- ing air powers. In this connection a word of warning is well sounded. Our present favorable posi- tion in airplane and engine development is 43

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Featuring a wingspan of 150 feet and powered by four 1,000- horsepower engines, the Boeing XB-15, or “flying fortress” as it is popularly known, is believed to be the largest and fastest bombing plane in the world. The development of these huge planes necessitated a complete revision of military air tactics. Piloting is only one. phase of the intensive training of a modern military flyer. Shown above is a cadet class at Randolph Field, Texas, practicing radio transmitting and receiving, or “buzzer” as it is termed by the student pilots, the messages being sent in dot-dash- code. Airplanes can’t fly unless trained ground crews keep. them in. first condition, so Uncle Sam trains mechanics, too (above). 44 8 due primarily to the funds and effort we have expended during the past twenty years in funda- mental research and experi- mental engineering. During the years since the war, we in this country, the army, navy, National Advisory Committee for Aeronautics, Bureau of Air Commerce, and aeronautical in- dustry combined to spend more money on fundamental research and aeronautical experimenta- tion than any of the other na- tions. During the past year there has been ample evidence that several of the other powers realize fully the reason for our favorable position, for some of them are now expending vast sums on wind tunnels, experi- mental laboratories and engi- neering establishments. In three to five years, therefore, we may well expect, in fact it is a fore- gone conclusion, that these na- tions will surpass us in airplane excellence and performance. The only alternative is for us in this country to bestir ourselves and increase by at least one-half, and preferably double, our funds, resources and effort in aeronautical experimentation and research. Today, however, our position is an enviable one. Our newer planes surpass, for the purpose for which designed, the proto- types found elsewhere. There is not a four-engined, long range, high performance, high capacity bomber abroad which its owners would not gladly exchange for ur “Flying Fortress,” the Boe- ing bomber. There is not a Modern Mechanix fighter in any land which has created the stir and been ac- corded the adulation and praise heaped on our Bell “Airacuda,” multi-seater fighter, the world over. Our attack planes, of which the Northrop is the single engined version and the Curtiss A-18 the twin engine prototype, are preeminent in their fields. Our single seater fighters, Se- versky P-35 and Curtiss P-36, are excellent pursuit planes. Some fighters may be found abroad slightly faster, but few, if any, possess all the many characteristics, many of them antagonistic the one with the other, as are combined into these sleek, little, metal air destroyers. On the score of total numbers of military aircraft, five or six of the nations of the world ex- ceed the United States, but we take no small comfort that on the score of quality and unit effec- tiveness, there is little question but that we go to the head of the class. Air bases comprise an abso- lutely essential element in any effective air force. The finest planes in the world will be mired in the mud, inert and useless when needed, if proper basés are not available from which they can be cast into the air, groomed, manned, tuned up and armed for effective fighting might. Millions of dollars have been spent by the Army during the past few years in an effort to provide up-to-date air bases. There has been much improve- ment in living conditions for officers and men; shops, hangars, May, 1938 The “ground school” training of future Air Corps pilots involves attendance at lectures devoted to photography, navigation, aero- dynamics and a score of allied subjects. Shown above is a class attending a lecture on the operation of various aerial bomb sights. A class in soldering and brazing technique at the Air Corps Tech- nical School. Chanute Field, Ill; is shown in photograph above. 45

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OR years, Clyde W. Parke, of Memphis, Tennessee, had been hearing the jibes and laughter of his friends as they watched him toil away with penknife and scraps of lumber. For years he had given them the same friendly smile and the same good-natured answer: “You'll see. One of these days I’ll have the greatest circus in the world!” It wasn’t a facetious remark; it was a prophesy. For today Mr. Parke is the owner of the world’s most intriguing miniature circus. He is a modern Jonathan Swift, but on-a more magnificent scale. Both creators of Lilliput, Mr. Parke differs from his ancient contemporary in that the creatures of his vivid imagination manifest themselves in 48 Clyde W. Parke, of Memphis, Tenn. (right), whose skill as a whittler enabled him to create his famous miniature circus. Shown above is a section of the interior of the Parke Miniature ings and stages are only diameter or square. Pigmy figures carved in wood, instead of fictionized characters. For thirteen years, beginning at the age of 37, this versatile “Master Whittler” has whittled, scraped and gouged at bits of wood. He has accomplished a gigantic feat. His “show” is not a mere collection of carved wooden “people.” The Parke Miniature Circus is a vast congress of more than 300 animated lifelike actors and animals, each of which does something different. Every thrill- ing stunt you have seen pulled off by daring performers in the big shows is faithfully du- plicated by Parke’s mechanical midgets, which are whittled to the scale of one inch Modern Mechanix A view of the side show entrance to the miniature circus is shown above. Note the ticket wagon and ballyhoo posters. Right—A comic police patrol wagon exhibit. to the foot. The Big Top is replete with thrills galore. There are—but wait. The best way to see a circus is to go. So step up, folks, and join the long line of eager fans buying tickets at the bright little wagon. We have taken (in imagination) a turn about the “grounds,” which are all of twenty feet long. We have had our curiosity ac- celerated by the antics of Firenza the Fire Eater, Stiletto the Knife Thrower, and JoJo May, 1938 Circle, above—One of the tiny show’s floats— a Far Eastern Empress carried by slaves. Above —The menagerie tent with its animal wagons. The “Big Top” is shown in background of photo. the Dog-faced Boy. We have heard (in imagination) the husky bellowing of the barkers and spielers in front of the Side Show Tent, which is a three center-pole affair, six feet long, aflutter with gay banners adver- tising the wonderous sights to be seen inside. We have watched, goggle-eyed. the Sword 49

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Boasting a height of 18 inches, the giraffe realistically looks over the top of his cage. Swallower gulp a wicked looking blade: the Magician produce a squirming rabbit from nowhere; the Fan Dancer in seductive wiggles; and the Snake Charmer slithering amongst her venomous charges. With bursting curiosity we line up to get inside. With the big show coming off in a few minutes, we cannot spend much time in the Side Show. After taking in the lesser spectacles here displayed, we move toward the Big Top. First, however, we must stroll through the Menagerie Tent. This is eleven by three feet in size. Around the sides are the animal cages. The center is roped off for the elephants, zebras, camels, and other large grass eaters. There is a plentiful sprinkling of straw on the floor, and here and there a tiny bale of hay. At one side of the arena a long, spotted neck topped by an un- gainly head, rises above the high fence. It is the Giraffe and apparently all is well up aloft! The Main Show Tent merits some descrip- tion, On each side is the Reserve Seat section —eight sections of 80 seats each, with foot boards and backs. The spectators seated here are cooled by 16 midget electric fans. At last seated (figuratively), we glance around the sparkling interior. Countless tiny ropes hold up, with the aid of block and tackle, the pole assembly of the entire tent. Our eyes are dazzled by the clusters of lights around each pole. There is the trapeze rigging, the aerial wheels, and all the parapher- nalia used by the Eight life-like horses draw the gayly colored Band Wagon, with its rhythm- swaying musicians, as it enters the arena at the head of Grand Parade (right). 50 - (right) is a big favorite little actors. But we are not given long to indulge in these commonplace essentials. With a mighty flourish the Grand Parade enters the arena at one end of the Reserve Seat section, and all eyes focus upon this colorful display. First into view comes six prancing whité horses, drawing the band wagon resplendent in red, white, black and gold colors. The spirited, high-stepping chargers give us as much thrill as does the driver on the seat, swinging his reins and swaying his body to the mythical rhythm of the five-man orches- tra behind him. Immediately following this appears several floats. There is “Little Red Riding Hood,” “Peter Pumpkin Eater” and the “Old Woman in the Shoe” with all her brood. Then the most dazzling of all the floats—Queen of Sheba, seated on her gaudy throne, sur- rounded by realistic fire urns, and haughtily gazing out over the backs of her six white horses. On either side and behind her stand servants dressed in white, each waving a palm fan over Her Majesty. Still another float is that of some Far Eastern empress. She is seated on an ornate pal- ULL The Monkey Wagon with spectators at the midget circus. The monkeys, skillfully carved, are shown in typical simian antics. A llama and monkeys riding horseback are featured in this group of midget circus animals. All are carved from wood. anquin borne on the backs of six stalwart Nubian slaves. At her feet crouches a snarl- ing tigress. There follows the yellow and white wagon bearing a huge hippopotamus. He seems quite content even in his cramped quarters, since the bed of the wagon is composed of a tank of water (a glass top creating this illusion) where Mr. Hippo may take a dip. The Monkey Wagon causes a howl of ap- plause. Here several of the amusing little simians disport themselves in all the tricks known to Monkeydom. The next wagon might have arrived from Greenland. Giant icicles hang down over an icy blue background, while the roof is a replica of the flashing Aurora Borealis. Within, reclining in his proper environment of gleaming snow and icebergs, is a giant polar bear. There is a wagon of serpents and so realistic are they that many in the audience refuse to touch even the wagon! Following this are the gorgeously bedecked wagons with lions, leopards, kangaroos, gnus, a tank of seals, black bears, and many other animals. There is a ponderous rhinoceros, one of the rarest beasts in captivity, and several gangling giraffes. Mr. Parke here calls our attention to something that may surprise many of us: The giraffe’s tremendously long front legs are in reality no longer than his seemingly shorter hind ones. It is only because his shoulders are so high, causing his back to slant at a grotesque angle, that his front legs appear longer. [Continued on page 118] Even a Lilliputian circus must have a feeding time for its animals, as shown in the photo above where elephants, zebras and a_ camel tackle some strewn hay. Right— A polar bear nervously paces his wagon cage as part of the “biggest little show” routine performance. Majestically, two lions (above) survey spectators from their cage. Note the oil can atop one wagon. Above—Three of the unusually detailed me- nagerie circus wagons. Realistic enough to cause spectators to shiver is the miniature Serpent Wagon ex- hibit, shown above.

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Official records re- quire strict adherence to rules under super- vision of the A.A.A. OARING around an outlaw track in a warm-up lap, a racing driver noticed one of his front wheels wobbled dangerously. Quickly he pulled into the pit, where me- chanics found a front spindle broken. It was too late to change before the race. A few minutes later the car rolled across the starting line with the spindle welded. As the driver streaked around the course on the third lap, the welded spindle suddenly parted. His car left the track, rolling over and over. The unfortunate driver was picked out from a pile of smoking, twisted wreckage. Such an accident under American Auto- mobile Association control would never have happened, as the car would not have been allowed to start. Power to bar an unsafe car from the track belongs to a little group of technical experts who hold in their hands the lives and reputations of drivers upon the ‘Top—Muroc Lake is the scene of many gruelling car tests: and new records. Above left—Electrical tim keep an accurate check and furnish indisputable evi- dence of records. When endurance tests are bei „conducted, flares light the course during the night. Hour after hour, cars speed around the course while A.A.A, officials watch every detail of the test. wn 8 Modern Mechanix nation’s major speedways. Thats why the “Three-A” contest board is the supreme court of the racing world, and why its deci- sions are final. Perhaps you have seen the yellow flag sud- denly raised during an exciting contest. An A.A.A. man has noticed some unforeseen danger on the track, and drivers are warned to hold their relative positions until the green flag tells them of hazards cleared. Then they Here is a battery of electrically controlled stop watches. Large charts are kept and every lap accurately recorded. Every pos- sible precaution is taken to prevent slightest error in records. May, -1938 Error is reduced to a minimum by having = electrically controlled devices do all the me constantly by officials. must make a complete lap before applying a heavy foot to the accelerator. Just a short time ago, for example, a racing car broke an oil line, spilling oil on the track. Up went the yellow flag. All drivers eased their throt- tles until the green flag was raised to show the track clear. Long before the crowd fills the grandstand, A.A.A, men have been busy behind scenes. Cars have been inspected and then im- pounded to await the starting signal. All are thoroughly examined for safety, especially front axles and steering mechanisms. Speci- fied devices such as safety arms to prevent losing of wheels, and a fire dash between driver and engine compartment, must be carried. Ifa car is too light for good driving, the driver may not “slug” his mount by carrying sand-bags or other weight, unless it is built into the car. The hood must be fastened securely with two straps over it. If a driver loses it during a race, he must retrieve it next lap. The A.A.A. is the American branch of the parent association, the Internationale des Automobile-Clubs Reconnus. Racing clubs register as members, accepting its authority to rule on all mechanical phases of their con- tests. Disputes between drivers come before this court of the track for settlement. Some- times one racing pilot will accuse another of forcing him into a spin by crowding. A com- mittee hears the complaint, and if it cannot settle it, refers it to the national committee, which meets four times yearly in Washington. Six times in eight main-event races, a cer- 59

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TUNING UP THE se -aS E F YOU, like thousands of other sensible outboard motor owners, stored your motor away last winter in accordance with the clearly printed instructions that were supplied with the engine at the time of its original purchase you need only observe a few simple, common sense “tuning up” rules now in order to insure maximum efficiency throughout the dawning boating season. The first step is to go over the entire motor, tightening all screws and nuts. If a screw does not seat properly, do not force it, but unscrew it. Then, after dipping the screw in some heavy oil, try rescrewing again, mak- ing sure that you have engaged the threads properly. Remove the spark plugs and squirt some clean gasoline into the spark plug holes. Pull the motor over by means of the starter rope’ until the oil that was placed in the cylinders during the winter has been pretty well re- moved. 68 ‘OUTBOARD Ardent fishing enthusiasts are boosters” of the outboard engine because it en- ables them to visit widely separated fishing grounds within minimum time. Check the spark plugs for breakage and adjust the gaps according to the manufac- turer’s specifications. Test the plugs to see if they are delivering a good spark by at- taching each plug, in turn, to a spark plug wire (grounding one wire in the case of two, or more, cylinder types) and turning over the engine to see if a “hot” spark appears across the plug points. In the event you do not get a good spark, remove the entire magneto assembly and check all wires for breakage. The coil can be given a protective coating of water-proof varnish at the same time. Take the carburetor apart, as explained in the manufacturer’s instruction booklet (if you lost yours, you can obtain a new one from the manufacturer at a nominal cost), and remove all dirt and oil. Replace the gasket if necessary, as indi- Modern Mechanix cated by breakage or a dried out appearance. Clean out all old grease from the gear housing, wash the housing in gasoline and check the gears for breakage. Refill the housing with grease recommended by the manufacturer. (This is probably the most important of all pre-season precautions). Having tightened all screws and nuts, checked the plugs, magneto, coil, ete., as well as cleaned the carburetor and refilled the gear housing, you are ready to mount the motor on your boat. Start the engine in the usual manner, making certain that water is running through the pump within a few seconds or the cylin- ders will crack from the heat. Carefully adjust the carburetor until you are getting maximum efficiency and smooth running. Don’t “go off the handle” if the engine does not run smoothly at first, but check over all parts systematically until you locate the trouble. “Losing your head” won't get one single r.p.m. out of the engine. Modern outboards are practically fool-proof and when they do break down it can usually be traced to abuse by the operator. May, 1938 The knowledge that the outboard motor will eliminate the tiring job of rowing back to camp helps to make the fisher- man’s day more enjoyable (top) and enables the followers of Izaak Walton to linger at the choice spots until the last pos- sible moment without fear of missing “chow.” Above-~Hun- ters, too, find the outboard to their liking for there is nothing like the powerful ‘‘putt-putts” when it comes to traveling up- stream in a boat loaded with hunting and camping equipment. 69

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Head on, the “Weber Roadster” has a_strik- ing appearance. In the drawings below, the construction details of a simpler radiator and ood are shown. Above—when pushed for- ward, the hand lever causes the idler pulley to tighten the single drive-belt, mov- ing the car. Pulling lever back applies the brakes. HERE is one definite rule to follow in making a sidewalk automobile—get your engine first and build the car around it. This applies pretty much to the wheels, too. A half-horsepower, two-cycle washing machine engine is available in nearly all sections of the country, and as these can be had second-hand at a moderate speeds, they make satisfactory installa- tions. Herewith are working drawings of the little ear owned by Richard Weber, of San Marino, Cali- fornia, which is driven by this type of motor and has proved successful for a long t \ period. It is very easy to build. i s N 3 In Figs. 1, 2 and 3 are given the general is G over-all dimensions. Note that the front wheels have a wider tread than the rear. This permits a shorter turning radius, and brings the back wheels in close to the power unit. The engine is provided with Modern Mechanix reasonable price and have sufficient power for ` by Hi Sibley a kick starter, and the clutch arrangement consists of an idler pulley which tightens the single drive-belt when the hand lever is pushed forward. When pulled back, it K operates the brake. Drive is on one wheel, brake on two. Hood, seat-back and dummy radiator are of galvanized iron cut as shown in Fig. 12. These dimensions are approximate as a cer- tain amount of fitting is always necessary for curved members. If you have the facilities, May, 1938 %y % \ al Left—The trim little run- about is powered by a washing machine motor of one-half horsepower, which enables the car to travel about 16 m.p.h., averaging 50 to 75 miles per gallon of gasoline. Motor is connected to one wheel by a drive-belt. NAMEN, V2 RADIAT FILE FROOLISH SAN NUM: LLUMIN! The start of a midget auto “race”, with the Weber car in fore- ground of the lineup. 73

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the edges of the metal should be beaded. The

=? ies: Ma SS edge of the seat back is protected with a strip d ES AU of leather laced on with rawhide. It will be "o 3 ob Se F best to leave the cutting of the hood, etc., = AS SHOWN IN FIGO

FIG.5 — FRONT END OF CHASSIS SHOWING STEERING ASSEMBLY

“{ REAR END “| OF CHASSIS WITH DRIVE ee ANDBRAKING. — ~ DETAILS —

CLUTCH & BRAKE

RADIATOR ORNAMENT

FIG.3 FRONT VIEW

NAN

12" TIRE & WHEEL CLEVIS BOLT

A WELD 3/8" ROD COTTER PIN

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TOP PLATES OF 3/4" X 3" STOCK: CORNER POSTS OF x sa" stock — |] TOP SILLS OF ANY il SCRAP LUMBER pi i WALLBOARO “T i S i i IceLLULOD OR GLASS WINDOW i 1 i i 4 8 FLOORING z TUNNEL CABINET Shown above and at right are the general constructional de- tails of the cabinet, honey- comb air-straightener core and air pass of the novel model plane wind tunnel. The cir- cular sketch shows how the honey-comb core is constructed by notching and inter-locking strips of sheet metal. The sketches on the opposite page show additional details of the air pass construction as well as | complete details of the dyna- mometer assembly. Practically all parts are made from easily obtained scrap materials. N RESPONSE to numerous requests re- ceived during the past few months, Mopern Mecuanix is herewith reprinting plans and details for the construction of a miniature wind tunnel for testing model air- planes. This article, in its original form, appeared in the MM “Flying Manual,” 1932 edition, and was written by Dick Cole. Many experimenters have undoubtedly tried to test their models in the blast of air 76 ? AIR-STRAIGHTENER CORE (SEE DETAIL BELOW) ~ WALL BOARD 3/4" FLANGES- NAIL OR SCREW = TO END FRAMING HONEYCOMB CORE 18" X 46-V2" TO FIT INTO END OF CABINET OLDER OR WELD L AIR PASS OR CONDUIT (HEAVY TIN OR SHEET IRON) DETAIL OF CORE (SHEET METAL) from an electric fan, but, such tests are highly unsatisfactory for the reason that the wind created by the fan is a mass of whirling currents—a miniature tornado. To test a model plane successfully, it must be placed in a flow of air that is moving with equal velocity throughout its entire cross-sectional area, and the air stream must be free of whirling eddies. How this ideal condition is brought about is shown in the sketch illus- Modern Mechanix RUBBER BANDS STEADY MODEL ADJUST TO BRING POINTERS HARDWOOD END BLOCK FITS INTO AIR PASS L { STRAP IRON BRACKET SMALL POSTAL SCALE RECORDS "DRAG" 16" DIAM. FAN DETAIL, OF BLOWER FAN INSTALLATION trating the complete wind tunnel assembly. The principal parts of the model wind tunnel are a partially closed cabinet, an air- straightener honey-comb core, an air pass, a dynamometer assembly and an ordinary electric fan or a kitchen ventilating fan, such as is shown in the sketches. The electric fan sends a blast of air through the air pass and its only outlet is through the honey-comb air-straightener, which serves to emit the air in an even flow, creating the eddyless condition required to test the model plane. The model is mounted on a dyna- mometer, being completely exposed to the air flowing through the honey-comb core. The lift scale and drag scale, as shown in the sketches, will give a direct reading showing the effect of changing the positions of the [Continued on page 122] May, 1938 Ruse BINDER DIMENSIO AS FROM S CENTER To CENTER 3/4" Woo BRACKETS! SCREWTO FLOOR DYNAMOME i STAND DETAI 77

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OMEONE has described certain articles of furniture as possessing the quality of coziness. This quality is amply evinced in the small gate leg table, for it is both cozy and comfortable, and, furthermore, because of its attractive turning, it is a highly deco- rative piece of furniture. The person who is interested in wood turn- ing will undoubtedly find a friendly challenge in the construction of this article. Aside from the skill necessary to turn out six duplicate legs, the craftsman will not encounter any unusual complications in its construction. All construction is obvious and not in the least complicated. In making this small gate ‘leg table, place emphasis upon all those important “touches” which put good furniture across. Such “touches” include the proper dulling of edges (as indicated in the plan), the use of wooden pegs to both strengthen and lend a quaint crafty appearance to all mortise and tenon joints, and finally a proper finish to give life and warmth to the completed article. 82 If each part is shaped carefully, final assembly will be very simple. Although almost any wood can be used, either walnut or cherry is suggested, A thorough sanding before any finishing is applied will give a more pleasing appearance to the completed project. Plenty of rubbing with a soft cloth will give a warm and attractive luster to the finish. Any one of a variety of different woods can be used. It is recommended, however, that either walnut or cherry be used. Note that the sizes given below are of the finished stock. Stock should be cut slightly larger than these dimensions to make allowance for dressing and working to actual size. Turned Members: 2 pieces, 144”x114”x17%” (end posts) 2 pieces, 114”x11”x193¢” (gate posts) 2 pieces, 144”x112”x167%” (gate pivot posts) Because it is necessary to duplicate exactly the turning of all these members, it is suggested that the worker cut an exact and full size pattern of the turning before starting the operation. With this pattern as a guide, the craftsman can readily obtain the exact shaping desired. After the turning is finished, cut mortises and tenons, as indicated in plan, on various turned members. Mark and cut half lap cut-outs on ends of outer gate posts. Feet and Top Cleats: 2 pieces, 1144”x2”x8” (feet) 2 pieces, 144”x114”x4” (top cleats) Square to specified sizes. Mark and cut mortises. Cut pattern for foot shaping as indicated in graph detail. Mark this shaping on two opposite faces of each other. Cut and finish to exact shaping of pattern. Round under edge of top cleats. Assemble turned posts to feet and top cleats. Secure joints with glue and insert wooden pins while assembly is being held together under clamp pressure. These pins should be per- mitted to protrude 4” from surface. They are rounded off to give proper quaint pegged effect. [Continued on page 122] Before turning the legs the builder should make a full-size pat- tern. With this as a guide, no difficulty should be experienced in turning out exact duplicates. After the turning is finished, the mortises and tenons are cut. The dimensions of the curves shown in the detail can be varied to suit individual taste. TOP CLEATS. PARTS 545A xls MORTISE, 1“ DEEP PEG——>" w BOTTOM RAIL Wg DIAM. AY ETOP BATTEN

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EADERS of preceding articles on microscopy are now familiar with the parts and operation of a microscope, and have made studies of pond life, insects and other intro- ductory matters. They have made temporary slides and a few whole mounts that require little if any technique. So now is the time to take the next and the biggest of all steps in microscopy, and to learn how to cut thin sections and make really professional and permanent slides that can be preserved, sectioned, stained and mounted in balsam. This is a sizeable job and the whole story cannot be told in a single chapter. In the present installment we shall go into the details of cutting thin sections, and other stages in microtechnique will follow along in succeeding issues. Sectioning—the cutting of thin slices—is necessary whenever the material to be ob- served under the microscope combines thick- This is the eighth in a series of articles published by MODERN MECHANIX on this fascinating sub- ject of microscopy. Previous articles are as follows: April—"Documentary Evidence’—A study of the characteristics of handwriting and typewriting, and how the microscope is used to track down law breakers. “March—"The Silent Sherlock”—The microscope and its use in present day crime detection. February—"Finger . Prints in Fur’—How the microscope is used by the fur industry for identifi- cation purposes. December—"Hitching a Microscope to Your Camera”—How a camera can be used with a micro- scope to preserve the wonders seen by the eye. November—"The Autumn Empire of Insects”— The thrills of big game hunting are revealed under the lense of the microscope in the study of common insect species. October—"Microscope Reveals Mysteries of Life in Water”-——How to delve into the wonders of nature with a microscope as your magic key to the store- house of life at its conception. HOW TO CUT Homemade microtome is easy to build and use to get thin sections. At the upper left is pictured a cross section af a lily flower bud showing all the structural parts of a typical flower. At its right is a longitudinal section of a dandelion flower. Above is shown the hand microtome described in the text. ness with opacity, and this is usually the case. It is possible to secure surface views of such objects as skin, liver or heart, and of stems, leaves, stones and minerals; but generally it is impossible or inadvisable to try to make permanent mounts of most of these, and no information at all is obtained of the internal Modern Mechanix MICROSCOPE Y Julian D. Corrington, Ph. D. Plasticene models to show the planes to be fol- lowed in cutting sections. Radial object at left and bi- lateral at right. In the latter, card- board strips represent the three planes. structure or of the kinds of cells that make up plant and animal organs. Slices thin enough to permit the use of transmitted light are necessary and so a com- plicated technique of procedures has grown up to serve this need and to prepare the beau- tiful and permanent slides that are in com- mon use in high school and college courses in biology. If you have never seen this sort of slide we suggest that you purchase one from a supply house or dealer so as to have it as a model in making your own. Ask for a cross section of basswood or other tree stem or of lily flower bud, double stained. On the blank glass slide has been placed an ex- ceedingly thin section of the material, per- manently preserved against decay and stained with various dyes to give color and contrast to otherwise almost transparent structures. The section has been rendered translucent by means of an oil and has been placed in Canada balsam and then a cover glass added. After thorough drying to harden the balsam, the slide was cleaned and labeled. It is such a slide that we are going to make, taking one of the major steps this month. Advanced and detailed studies may require May, 1938 SECTIONS FOR YOUR sections that are not only very thin, but of a known and uniform thinness, and hence there have been de- veloped a number of types of precision in- struments known .as microtomes, from the Greek words small, and to cut, Some use a knife carrier that slides back and forth in a slot; others operate on the rotary principle and are quite similar to the rotary meat slicer to be seen in a meat market. Some one, in fact, referred to this style of micro- tome as “a glorified meat slicer.’ Ma- chine microtomes cost from fifteen to several hundred dollars. For all ordinary and prac- tical purposes, however, a hand microtome, as described in this article will do the trick and can be made by anyone familiar with the use of tools. First, though, there is the free-hand method of cutting sections which employs no micro- tome at all, and whether or not you plan to operate a microtome you should know and practice this system. Every microscopist worthy of the name should go through this step in his training and acquire a bit of the necessary manual dexterity, so often lacking in this machine age. Recommended as practice material at this season of the year are leaf buds from trees, particularly the larger types, such as horse’ chestnut. The knife may be either the old- fashioned razor, as shown in an accompany- ing illustration, or a safety-razor blade held in a carrier with folding handle—an object commonly sold in the five and ten cent stores. The stiff type of blade is better for our pur- poses than the flexible one. New blades are readily inserted in the carrier when the one in use becomes dulled. Hard woods 85

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by Dick Cole ISHING can probably be classed as one of the most universal and cosmopolitan of all outdoor sports. It is quite safe to say that it plays a part in every man’s life at some time or other, perhaps beginning with a hick- ory branch, grocery store cord and a bent pin, and leading up to the prized possession of a “Thomas” or “Hardy” rod, taper lines, and a vast collection of lures and flies. Fishing—angling—is becoming a truer sport every year. Our forefathers fished solely to get fish. We of today fish for the joy of outwitting the fish with artifice. Our forefathers’ tackle consisted of a solid bamboo “pole” with a length of 10-cent linen line tied to it—no reel; eyed hooks at 5 cents a dozen, a can of worms and a rusty nut for a sinker, The angler’s tackle of EMERGENCY REPAIR FOR BROKEN ROD TIP SS a taal Il Zz SQUARE UP ENDS AND DRILL HOLE WITH SMALL DRILL ~ (NO 50,55, 60) NEEDLE Su TAPER ENDL- INSERT SECTION OF NEEDLE-COAT SURFACES WITH CEMENT AND PRESS TIGHTLY TOGETHER => Tl p WRAP TIGHTLY WITH SILK THREAD AND APPLY CELLULOSE CEMENT OVER WRAPPING PIN TO TIGHTEN MALE Boor EATE FERRULE, DRILL HOLE. THROUGH’ METAL END- DRIVE A PIN OR NEEDLE INTO CORE OF WOOD TO TIGHTEN A FEMALE FERRULE FILL ENO WITH WATER AND BOIL IT OVER AN ALCOHOL FLAME. PLACE ROD SECTION IN VERTICAL POSITION UNTIL WOOD DRIES OUT AND GLUE RESETS A DAMP CLOTH DRAPED OVER CREEL, KEEPS FISH FRESH IN HOT WEATHER FOR APPLYING DRESSING TO LINE OLD NAIL FILE GLUE FINE EMERY CLOTH TO SIDES TO MAKE EXCELLENT TOOL TO SHARPEN HOOKS TO KEEP BROOK TROUT IN GOOD CONDITION CLEAN IMMED~ IATELY UPON CATCHING -WIPE DRY AND ROLL EACH FISH SEPARATELY IN WAXED PAPER Broken rods can be quickly repaired by splicing the break in the manner described in the details at upper right. Lower illus- trations show how a loose fertule may be tightened simply by heating it over a canned heat flame. To ward off annoying insects the fisherman may attach lengths of old fishline to the brim of to split a piece of varnish-rubber felt to form an applicator. 88 his hat. A quick way to apply dressing to a fishing line is To keep fish from spoiling, clean and wrap in waxed paper. Modern Mechanix today can easily run into three, or even four figures. However, to gain full enjoyment of angling as a sport, it is not necessary to invest a large sum of money. Perhaps a $10.00 domestic rod will not handle a $2.00 “level” line with the same nicety that a $150.00 tournament rod will handle a $15.00 double taper line, but, when the two outfits are put to actual use on a stream, maybe the $12.00 outfit will out-fish the aristocratic equipment. It really is the man at the butt-end of the rod that decides the issue. It is not the intention of this article to give a treatise on the art of bait and fly casting, but rather to pass along to fellow anglers a few little kinks that may aid them in gaining a fuller enjoy- ment of their favorite sport. What can be more annoying than to break a flyrod tip section far from camp? However, a satisfactory repair job can be made right on the stream if the angler carries some simple equipment with him. This consists of a packet of needles of assorted sizes, a tube of celluloid cement, several small twist drills—say, No. 50, 55 and 60—and a spool of strong silk thread. To proceed with the repair job, the broken ends ~a TAPER LEADERS 24" MADE OF SYNTHETIC SILK WORM GUT AND TREATED WITH AIRPLANE DOPE SERVES VERY WELL FOR DRY FLY CASTING SOAK GUT AND FORM KNOTS- aes TIGHTEN AND PULL x ¥ f) TOGETHER BLACK HACKLE FLY REMODELED INTO ROCK WORM - VERY EFFECTIVE "WET FLY" IN SLIGHTLY DISCOLORED WATER WRAP BODY WITH ALTERNATE TURNS OF BLACK AND YELLOW YARN SPLIT BACK FIN AND TAIL TO IMPROVE WRIGGLING GANG HOOKS] GOOD LURE FOR PARTLY CON- CEALEO UNDER Fins ALL GAME FISH May, 1938 For Tug Fis “LAMPER" EEL OR ANGLE WORM MADE OF BACON RIND VERY EFFECTIVE FOR WALL~EYED Every fisherman derives more satis- faction from the sport when he is able to land his catch with lures of his own creation. Several effective lures are shown above. A black hackle fly can be made into an effective “wet-fly” by wrapping the hook with alternate turns of black and yellow yarn. A good lure for all game fish can be made from bacon rind as shown in the lower detail. 89

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A simple rack will sup- port the tomato vines when they are heavily laden with fruit. Any scrap lumber will be satisfactory. A coat or two of paint will make its appearance much more pleasing. To insure a good tomato crop, fertilize the seedlings generously so that they will become tall and spindly. Scoop out earth at one side and bend the stem down into cavity and cover it with earth to within a short distance of the end. “PART OF STEM BECOMES ROOT This sweet-pea trellis of galvanized pipe and wire can be pulled up and moved to a new spot each season. When the vines have withered the trellis can be pulled up and stored to make room for any. other plants. Modern Mechanix This easily con- structed wood trencher makes uniform rows when it is pulled along a string stretched along the path to be fol- lowed. Dimensions can be varied to meet the individual builder's needs. 9” LONG When the task of caring for the lawn becomes tire- some, considerable work can be eliminated b: s SHAPE OF ful planting of annuals. TRENCH The taller ones should be placed near the house. VERY amateur gardener has been confronted with at least one of the problems solved here, such as the burden of caring for the lawn after the spring enthusiasm fades. An old-fashioned flower garden, once established, does not re- quire exacting care. You may have old trees whose foliage is spindly—feed it vitamins When a drain slope is as great as 45 degrees, rocks should be embedded in the earth, An incline using plain sod should not be permitted to exceed 30 degrees. 3YX 12 a“ TILE PIPE A three-inch drain pipe set into the ground is a convenient means of feed- ing tree roots. The pipe can be filled with fertilizer and then filled regularly with water. In some loca- tions this is the only way trees can obtain sufficient moisture to exist. May, 1938 through drain tile, or water through a perforated pipe that reaches the deeper roots. The seed trencher is easy to make, and the sweet-pea trellis a great convenience. Tomato vines pro- duce a surprising crop when started right in youth. And that dried out and trampled terrace can be greatly improved with a rock garden. 93

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CHOOSE THE RIGHT BRUSH O YOU really enjoy the creative work of wielding a paint brush? It can be just as interesting and as pleasurable a recreation as any other workshop hobby. One de- terrent to “having a good time while decorating” is the use of unsuitable materials. Of course it is neces- sary that you work with a good quality of paint, enamel or varnish, but just as im- portant is the choosing of a brush that is exactly suited to the job. This informa- tion comes not from the brush manufacturers but from skilled profes- sional decorators, who know how to turn out first class work because it is a matter of pride and repeat business. First, they say, pay no attention to the size or shape or weight of the handle, nor how the brush bal- ances in your hand. If it is of a reliable make, the manu- facturer has provided a handle that is adequate in all respects. The important part to examine is the bristles. You will not find good bristles in cheap brushes. Master decorators consider it a worthwhile investment to pay up to $5.00 (and sometimes three times that amount) for a brush with which to do their best class of work, so it is to be expected that only very inferior ` work can be done with one purchased for 10c. A good rule is to use as fine a brush as you ean afford for the quality of work to be done. With practically all types of brushes the quality is dependent on two points: first, the bristles should be springy, elastic and full of life. They will not spread paint well if they are coarse and stiff, and are likewise unsat- Opposite page—Several types of brushes needed for all- around house painting. Left—A sheet of cellophane makes an excellent moisture-proof holder for a brush. Top of page —The correct way to hold a brush. Right—To paint the inside of a narrow space where the hand can not reach, screw an old brush to the end of a broom handle as an extension. 94 Modern Mechanix May, 1938 95

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Close inspection of brush bristles A new brush can be tested for stiffness by piessing. it against the ack of the hand. The bristles should be springy and full of life. isfactory if they can be bent in any di- rection without resistance. Secondly, examine the ends of the bristles by fan- ning them out between the fingers. If each is well “flagged,” or split into two or more smaller branches, they will do good work. The flag ends will enable the brush to hold more paint and will spread it out better. Choose a brush of the correct size and type for the work you wish to do. If you are not sure about the one to use ask the dealer. The bristles should not be too thin or scanty. ` While a narrow brush is desirable for narrow work, it may leave markings when brushing out the paint on a wide surface. The length of the bristles is important and the longer they are, the better the brush. Then notice whether the bristles are set in glue, rubber or cement. If the brush is of good quality, either of the three types will be satisfactory for its purpose, but with a cheap brush the setting will allow occasional bristles to loosen throughout its life. A glue-set brush will not be satisfactory if it is to be put in water, while one set with ce- ment should never be used with a finish containing alcohol, such as shellac, or in quickly reveals the presence or lack of “flag ends.” Their presence is an indication of quality. Modern Mechanix Above—Use a coarse comb to work the cleaner deep into the heel so that every trace of paint is removed. Above right—The result of improper clean- ing and care of what was a good brush. the more volatile solvents such as are contained in quick-drying lacquer and lacquer thinners. The rub- ber-set brush may be used for all around purposes and will prove most generally suitable. There may be a few loose bristles in the new brush, even of good quality, and it is a good practice to flick them out beforehand by slapping the bristles Į across your fingers a num- Ë ber of times. If trouble £ from loose bristles is expe- rienced later, it may be due to lack of care in cleaning and preservation. For outside painting jobs most master painters use flat brushes in several widths, with black Chinese bristles set in rubber. For general work you will need one three or four- inches wide, and for sashes and trimming a narrower one with a longer handle (known as a trim brush), either round or oval so that it will carry more paint. With these, as well as with brushes for interior work, you should have a flat duster about four inches wide to clean up the work ahead of the paint brush. While a duster is not absolutely necessary, the quality of your work will be greatly im- proved. For enamel and varnish some painters use a good grade of black Chinese bristles, but when questioned they usually admit that for particular work their preference turns to a May, 1938 Cleaning a brush imme- diately after using it will keep it in first class con- dition for years. Below —A large coil spring will hold the tip of the brush in the paint. soft flowing Fitch brush. Bear and ox hair also come in the latter class. While for ordi- nary painting you will use a square-end brush, varnish and enamels should be flowed on, and for this reason the chisel end is usually chosen. For ordinary work use one about three inches wide, and if possible have on hand smaller brushes for narrow work and trimming. For walls select a four-inch Chinese bristle; floor can be handled nicely with a two and one-half-inch flat or oval, the latter being given the preference. In general, use a brush to suit the size of the surface to be finished, and do not try to use [Continued on page 132] 97

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THE ‘TIN 174" x 178" : K Parts BRASS 172" DIA. HOLE. INSERT RED CELLULOID WINDOW NEGATIVE HOLDER GROOVES FOR NEGATIVE HOLDER AND DIFFUSION GLASS, MAKE TWO NEGATI HOLDER The view finder of the camera provides a mounting for the enlarger’s lens-filter (top sketch), construction of which is described in text. Center sketch—-Construction details of the grooved blocks, which accommodate the negative holder and diffusion glass, as shown in sketch at top right. Two pieces of hinged negative glass comprise holder (above). 104 from an old folding camera plus a tin can and a few easily obtained inci- dentals are all that are required to con- — struct the photo en- larger shown above, — yar HOLDER SCREWED TO SIDE OF T NEGATIVE BOX CAN SPECIAL” OPENING FOR NEGA- TIVE HOLDER AND DIFFUSION GLASS NEGATIVE GATIVE BOX HERE are probably few MM readers who do not have an old Kodak or other kind of small folding camera laid away in the bottom of a drawer about the house. In most cases, these have long outlived their usefulness, but the author found an old and battered Kodak No. 2, with its lens and bel- lows still intact, and considered the idea of making an enlarger out of it. A few scraps of wood and metal, an old tin can, and a piece of glass resulted in a rather nifty-look- ing piece of apparatus which surprised its not too hopeful builder by turning out fine 8”x10” prints from negatives as small as those used in the popular miniature cameras. With a photoflood as a light source, the printing time of the home-built enlarger is as fast as that of commercial enlargers with Modern Mechanix GROUND= GLASS -SCREEN BOX CUT OFF TO TAXE ASSEMBLY NO. 1 148" WIDE -SLOT FOR DIFFUSION GLASS A Practical Photo Enlarger much faster lenses, while the quality of the prints leaves lit- tle to be desired. When one considers that a mechanically flexible and rugged job can be made for a ridiculously small amount of money and work, there seems to be no reason why any camera enthusiast should not make his or her own enlargements. The horizontal type of construction was used because of its inherent stability and simplicity. In the instructions that follow, it should be remembered that the dimensions given in the drawings are for the Kodak No. 2 folding camera. The necessary modifications for a camera of different size can be readily made. Some minor “operations” are necessary on the camera itself. The back of the camera is removed and can be discarded, since it is not used in the enlarger. Make sure, how- ever, to salvage the little red celluloid win- dow, as it will be useful in making the lens filter, which is placed before the lens when sizirig the image on the printing paper. The camera should now be opened, and all ex- traneous parts removed from the base. This includes the distance scale, the tripod socket, the closing catch, and all miscellaneous rivets and screws except those which hold down the track on which the lens mount slides. Drill four holes, one in each corner of the base, for holding down the camera. Wood screws are driven through these holes into the wooden baseboard assembly, as sketched above. The bottom block of this as- sembly should be sand-papered on its sides and bottom, since it slides on the enlarger base, as the photographs and sketches show. The total height of this whole assembly is such that the lens is on a direct line with the center of the easel. CAMERA~WITH BACK AND ALL EXTRANEOUS PARTS REMOVED LENS BOARD SLIDE TRACK SCREWS TO HOLD CAMERA ry vien WIDE J4 SLOT FOR 4 CAMERA A CAMERA MOUNTING WOOD BASE ASSEMBLY _ SANDPAPER SIDES AND BOTTOM ENLARGER BASE TO SLIDE WITHIN RUNNERS ON EASEL The sketch at top of page shows complete details of the camera mounting on the wooden assembly base. Above-~Completed easel and enlarger baseboard with camera mounting slide- guides. A tin can serves as lamp housing for enlarger (below). since it can be swung around in and out of position. The small right-angular box hold- ing the ground-glass screen is sawed off flush The view-finder on the camera provides a convenient mounting for the lens-filter, May, 1938 and then filed clean. Short lengths of brass rod are then soldered on the screw and nut 105

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These three The view above was taken on a dull day with regular super- sensitive panchromatic film, 1/50 second at f.14, without a filter. The heavy clouds in the sky are barely perceptible. ictures graphically show the value of lens filters. Films of the “pan” type (“panchromatic”) respond to the entire visible spectrum, from the ultra-violet up to and including red, and therefore they register red objects as gray tones of varying depth; also, they must be opened only in complete darkness, as no “safelight” is longer “safe” for them. How- ever, regardless of the type of film, they still are most sensitive to the ultra-violet, violet and blue. Sky light is especially rich in these colors, a fact to be kept in mind. Photographers use cameras to make per- manent records of what their eyes see, but unfortunately, the color sensitivity of the human eye does not coincide with that of films. The eye is most sensitive to green, less responsive to blue and violet, and totally blind to ultra-violet. Thus, a landscape that appears gorgeous to the eye because of rich green foliage and blue sky turns out to be a very disappointing photograph when made on ordinary film. In the black and white print the trees and grass look too dark, the sky too-light. This is easy to understand now, because we know that the ultra-violet, violet and blue light of the sky registered much more strongly than the green of the 108 fields, throwing the photographic picture en- tirely out of balance with the visual picture. To restore this balance, we must restrain the powerful blue rays without affecting the other colors; for this purpose we put a piece of colored glass or other transparent sub- stance in front of the camera lens, and we call this attachment a “filter.” The name fully describes the action. Light rays of any desired color are allowed to pass through to the camera, while others are en- tirely or partially absorbed, and therefore have no effect'on the film. There are dozens of different shades of filters, intended for This is the same scene, taken a few seconds later with a K2 yellow filter, 1/50 second at f.11. The clouds now show fairly well. specific applications in many photographic fields, and their study is an extremely in- teresting one for the advanced experimenter. For the amateur, however, one, two or at the most three filters will take care of all ordinary requirements in pictorial and land- scape work. Any object will appear colored if by its nature it eliminates one or more of the com- ponents of white light. Grass appears green, for instance, not because it reflects green but because it absorbs blue on one side of the Modern Mechanix spectrum and red on the other. A red filter looks red because it absorbs blue and green. A piece of glass which holds back only blue light looks yellow to the eye because it passes red and green, and a mixture of these colors becomes yellow. It is obvious from the landscape problem that a yellow filter would have saved the picture by restraining the sky light. The yellow filter, in different depths, is unquestionably the most useful of all. It is in- valuable for outdoor scenes in which the sky shows prominently, because in re- straining the ultra-violet and blue of the actual sky, it makes white clouds stand out beautifully. A yellow filter in many cases means the difference between an ordinary snapshot and a prize-winning salon mas- terpiece. The “Kl” is a pale yel- low filter and is used when a short exposure is more important than a high degree of correction. The “K2” is the most popular and widely used filter in photography, and brings out clouds more definitely than the Kl. When used with super-sensitive panchro- matic film in daylight, a very close approxi- mation to true orthochromatic rendering of the subject will be obtained; that is, all colors will be registered correctly. It can be used very successfully with any of the “chrome” films. The “G” is a deep yellow “contrast” filter, and cuts through atmospheric haze effectively. It is also useful in providing good contrast between snow and shadows in snow scenes. The “XI” is a pale green filter designed to give complete color correction with super-X panchromatic and Panatomic film in daylight. Such occasions arise, for in- stance, with flowers containing a mixture of red, yellow and green. The XI is also helpful in making photos of a person’s face against the sky. Under artificial light, the X1 is used with super-sensitive panchromatic film for complete correction. The XI cannot be used with other than pan type films. May, 1938 Still the same scene, but photographed through an “A” red filter, 1/50 second at f.7. The sky looks almost black. The X2 is a deeper green filter, and is used with super-X and Panatomic films for correct color balance in black and white with arti- ficial light. It has no use with daylight. The “A” filter is red, and is of special ad- vantage is recording clouds against the sky, making the latter come out almost black. Pictures.taken in full sunshine with this filter sometimes have a night-time appear- ance. Some startling effects can be obtained with this filter if it is used carefully. A second feature of the use of a yellow filter is the better detail recorded of distant objects. During the summer, distant hills appear somewhat hazy because the haze (which is due to fog-like accumulations of moisture) scatters blue light and tends to blur scenes seen through it. However, it [Continued on page 120] 109

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SINKS FOR CAMERA FANS GLASS CUTTER EMBOSSES PRINTS An ordinary glass cutter supplies a convenient method of embossing the border of prints. Do not apply too much pressure to the cutter. SPRING SPEEDS CUTTER When trimming prints, the cutter blade action can be speeded up considerably by using a spring to raise the blade, as shown in the photograph. CARD SIMPLIFIES FOCUSING $ STRAP HOLDS TRIPOD A white card ruled with black lines as shown in the A book strap fastened to the tripod as shown in the photograph and attached to a flashlight, simplifies photograph becomes a convenient handle. It then focusing when a ground glass is used. can be carried like a suitcase. 110 Modern Mechanix A FILE DECORATES BORDER A raised design on the border of prints can be obtained by placing the edge of the print on a file and rubbing the paper with a hard object. CAMERA IDENTIFICATION By fastening a piece of adhesive tape on which is printed the name and address of the owner, to the inside of a camera. it can be identified if lost. May, 1938 STRING AIDS PAPER REMOVAL A piece of string fastened to the top of the box containing printing paper, and passed under the pile, simplifies removal of one sheet at a time. TONGS MADE FROM CLOTHES PINS By sharpening the points of spring clothes pins, they can be used as print tongs. An ordinary file or sanding wheel quickly shapes the required points. 111

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