Popular Science Monthly 1921-04: Vol 98 Iss 4

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Popular Science Monthly Waldemar Kaempffert, Editor April, 1921; Vol. 98, No. 4 25 Cents a Copy; $3 a Year

TECHN LCGY Copy Published in New York City at 225 West Thirty-ninth Street

= How Much The portable photometer will tell you crowd themselves into a single inch of space. With due apology to Einstein, we may say that, for all practical purposes at least, these light waves travel in straight lines. When they strike a highly polished reflecting surface, they are reflected off again in perfectly streight lines. Upon coming in contact with a white, rough surface, bod thousand light waves 25 a beam of light is broken “A up into a number of 3 Od smaller rays that strike 4 off by themselves in s.. 48 divers directions. ae We have long known 37 - how to produce light, 59 but it is ony recently . . that we have discovered the correct way to use it. Uncontrolled light is 24 — destructive, like many : 7 other uncontrolled nat- " 33 I ural forces. When light 1 - is reflected from a highly 1 oe polished = surface, it ; strikes the eye in a con- 2? centrated beam. Such reflection produces glare, : and glare injures the » - eyes. With the indirect system of 4 § lighting, the light is first directed 3 § against a rough reflecting surface like a plastered ceiling or wall. The

39 ESS 39 Btriking ZA 42 Surface WF - rerrectes beam FX, ,,G|| I fi — Mirror or Polished Metal. a striking SS surface SS;

Plaster,Wood or Rough Glass How a plastered surface reflects light. The beams striking the sur- face are broken up into smaller beams that leave the surface in different directions. No glare is produced and a softer light natu rally results

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Popular Science Monthl, Tapping the Earth’s Interior for Power A great reservoir of energy for possible future use CUBICAL block 8 miles high, A 8 miles broad, 8 miles deep— 4 &% such, it is estimated, is the total stock of coal beneath the United States’ soil to a depth of 3000 feet. Fach year a slice is taken off this block. In the last hundred years 210 feet were brought down. But this is no indication of the rate of consump- tion, for in the year 1917 alone as much coal was mined as in the first sixty years of the century of coal pro- duction. If we continue to consume coal at the present rate, the entire block will be burned up in about 4000 years. Judging from past indications, exhaustion will come much sooner. In other fuels the situation is even worse. The Geological Survey esti- mates that more than 40 per cent of our mineral oil has already been con- sumed, and that the remainder can hardly last twenty years. Fuel Gone—What Then? Do you realize what this means? It has been remarked that, “back of every man in the United States, reenforcing his strength for the year’s work, there is the energy of 634 tons of coal.” How, then, is the work of civilized communities to be accomplished if this backbone of our industries is taken away’? The situation that may con- front us before many generations have passed will be far more desperate than the greatest catastrophes of history. What other sources of energy are available? Wind, wave, and tide are not likely to contribute much more to our needs in the future than they have in the past. There is, of course, much available water power running to waste. But water power has its limita- tions. Then, still waiting for solution, there is the problem of the direct utilization of the sun’s radiation. This is likely to play an important part. But there is another source almost wholly untapped. We are sitting on a furnace, so to speak. No one knows, even approximately, the temperature inside the earth. Actual measure- ments made in mines and deep bore- holes show that, on an average, the temperature rises about 1° F. for every 60 feet that we go down. If this rate of increase continued to the center, we should have there a temperature of over 300,000° F., an utterly impossible figure, far ex- ceeding our estimates of the temper- ature of the sun. Professor Strutt, the English physicist, supposes that the temperature rises uniformly to a depth By Alfred J. Lotka Sir Charles Parsons, the distinguished English engineer responsible for the steam turbine of to-day, has made the startling suggestion that a bore-hole be sunk deep into the earth. His prime of 30 miles, and after that remains con- stant at 2700° F. Whenever a volcano boils over, we have striking evidence of vast amounts of energy going to waste, or even caus- ing destruction of property and human life. Not only in volcanoes is this waste going on. The earth is giving off heat day and night. We remain uncon- scious of this because the flow is steady, and, except in direct sunlight, we have no ready means of distinguishing between the heat contributed from the earth and that derived from the sun. 20 Courtesy of Hoppe object is the exploration of the earth’s crust, but he has also in mind the tapping of the earth’s stores of internal heat for power. The earth gives off this heat constantly day and night In point of fact, the heat given off b) the earth is by no means trifling. It is sufficient to melt, in the course of a year, a layer of ice covering the entire earth to a depth of 4 inches. To put the matter in another way, it is th equivalent of about 5 horsepower a! acre of the earth’s surface. Italy Runs Engines with Volcanoes For practical purposes this stream o! energy is too slow, even if it were jn a form available for mechanical pur poses, which it is not; for heat energy a.so ¢ locat unev evide we, | can | draw in t Italy you To-d from elect Tl mari not yard grou “i O: are ° engl turb into

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= eS Ol nha By Apri, 1921 ‘ in order to be useful, myst be pre- sented at a temperature different from ° that of its surroundings. At the earth’s surface the heat comes out, of course, at practically the same temper- ature as the surroundings. But suppose we dig down into the earth. Then we can draw out heat energy in available form—that is to say, at a high temperature, much as we would draw water from a well. We can also choose a favorable spot at which to locate the plant. The earth’s heat is unevenly distributed. It is more in evidence in volcanic regions. Just as we, in certain parts of this country, can push a pipe into the ground and draw off natural gas for our houses, so in the neighborhood of Lardarello, Italy, if you want to run an engine, you simply tap the earth for steam. To-day. more than 10,000 horsepower from this source is converted into electrical energy. The Lardarello development is pri- marily of local interest. We can not all get steam from our back yard by going a few feet into the ground, ‘Dig Down Twelve Miles,” Says Parsons, “and Take Power” Of more general interest, therefore, are the plans discussed by the British engineer, Sir Charles A. Parsons, of turbine fame, to make a deep bore-hole into the earth. - His prime object is the exploratian of:the earth’s crust, but he has alsolin Mind the recovery of power from such bore-holes. Sir Charles Parsons proposes the sinking of.a shaft to a depth of twelve miles. Can it be done? Would not the pressure of the overlying rock at that depth cause the sides of the shaft to collapse? How does the pressure inside the earth increase as we go down? This pressure would be easily computed, for any desired depth, if the earth were liquid (molten). On this assumption, it is found that the pres- sure at the center of the earth reaches the respectable figure of 3,000,000 at- mospheres, a pressure that would com- press the air in aroom13 by 17 by 8 feet to a space of 1 cubic inch, if ordinary laws held at such high pressures. But, in point of fact, the outer crust of the earth is not liquid; it is solid. Each layer forms an arch, supporting the layers above and thus protecting the layers below. This, of course, would tend to reduce the pressure at the center. But inas- much as there has been time, in the millions of years that have passed, for these arches to be crushed and to crumble, the estimate of the pressure at a given depth within the earth, based on the assumption that the earth is liquid, probably comes nearer the mark than would at first sight be expected. Professor Frank D. Adams has car- ried out some experiments to deter- mine the “zone of flow’’ of the earth’s crust—that is to say, the depth at which rocks fail to sustain the load above them, and would give way to inequalities of pressure in the same way that a sticky liquid like molasses does. He concludes that for limestone this depth is probably not less than 15 miles, while for granite 30 miles would probably be practicable. The engineering problems to be faced in sinking a shaft even 12 miles would not be trifling. The air pres- sure would be doubled every 3 miles down. This would necessitate the in- stallation of air-locks at every second or third mile. A Gigantic Ice-Box to Keep the Workers Cool A cooling plant would have to be built. If we assume a rise of 1° F. for every 60 feet of depth, at a depth of 12 miles a temperature of over 1000° F. would be reached. Sir Charles Parsons, however, bases his plan on the assumption of a temper- ature of 272°. He suggests, for the cooling apparatus, two large steel pipes, an upeast and a downcast pipe, connected at top and bottom every half mile, to form a closed ring. This ring would be filled with brine, which, - by natural circulation, would effect- ively carry away heat. The circula- tion, assisted by electrically driven pumps, would be capable of carrying In order to tap the earth’s interior for power, Sir Charles Parsons proposes the sinking of a shaft to a depth of twelve miles. Nothing comparable with such a huge hole is to be 21 found on the earth. But we present this picture of iron-ore mining because it gives some idea of the way in which large-scale mining operations are conducted

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Popular Science Monthly Soret ee If any one argues that it is fantastically impossible to tap the interior of the earth for power, let him turn to Italy and see what she has done. 22 DIAGRAM OCF APPARATUS FOR UTLLISING ENERGY OF NATURAL STEAM There the energy of volcanoes is used practically. In the neighborhood of Lardarello, if you’ want to run an engine, you simply tap the earth for volcanic steam. os Qmpnre M anthl,,; T is p $25, com L has thro find We pole mile hole dee] S stat the bull avel crus a 4

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April, 1921 enormous quantities of heat to the sur- face. At each half-mile stage there would be transfer of heat from the ring above to the ring below by means of an apparatus similar to a feed-water heater, or to a regenerator, constructed of small tubes, through which the brine in the ring above would circulate, while the brine from the ring below would pass through the spaces around the pipes. At the top or at intermedi- ate points the brine would be cooled by refrigerating machinery. Into the Bowels of the Earth The cost of boring the 12-mile shaft is placed by Sir Charles Parsons at $25,000,000, and the time required to complete the task at 30 years. Let us suppose that such a bore-hole has been made, cr even one going right through the ear What would we find the inside of the earth made of? We can only guess. A shaft bored from pole to pole would be nearly 8000 miles long, whereas the deepest bore- hole in existence is less than 114 miles deep. Still, there are some things we can state with assurance. It is certain that the core of the earth is denser, heavier, bulk for bulk, than the crust. On an average, a cubic foot of the earth’s crust weighs from 160 to 175 pounds. Now, the earth as a whole has a mass of 614 million billion billion tons, while its volume is about 38 million billion billion cubie feet. Hence, on an average, taken through the entire vol- ume of the earth, a cubic foot weighs about 341 pounds, or about twice as much as the material at the surface. This is not very astonishing. There must be a general tendency for the heavier substances to gravitate toward the center. We have noted that the temperature increase with depth observed at the surface can not possibly continue to the center of the earth. Nevertheless, there can be little doubt that the temperature rises above the melting- point of the rocks of the crust. Is the core of the earth, then, a sea of red-hot molten lava? This does not follow. At the high pressures prevail- ing, as we have seen, in the interior, melting may not occur, in spite of the high temperature. We can form a picture of the earth’s internal condi- tion from phenomena observed at the surface. Earthquakes, for example, tell us much. Their speed has been measured, and the measurement proves that the earth inside is rigid and not liquid. Then there are the tides. If the earth had a perfectly liquid core, thinly covered with a yielding crust, we would observe no Mee ee eh CC How Italy Makes Volcanoes Drive Her Machines 4 tion companies. Morethan 10,000 horsepower from this source is converted into electrical energy and distributed to villages and trac- Lardarello gets steam from its back yard tides at all. Why not? Because the land would heave in unison with the sea. On the other hand, if the earth were perfectly rigid, the tides would attain a maximum. From the tidal effects actually observed, which fall between these two extremes, but much nearer to the latter, the rigidity of the earth was estimated by Lord Kelvin to be somewhere between that of glass and that of steel. More recent esti- mates place it higher, making it about one and one half times that of steel. Since we are discussing the various observations that might be made in a deep bore-hole, we may briefly con- sider how the force of gravity varies inside the earth. If the earth were a perfect sphere of uniform density, the weight of an object would diminish continuously as it moved from the surface to the center of the earth, and at the center bodies would have no weight at all. Suppose a complete tunnel were bored from pole to pole, and a stone dropped into it. What would happen to the stone? It would fall for about three quarters of an hour, by which time it would have reached the opposite pole; it would then start falling back to the center, oscillating like a pendulum. In- cidentally, its period of vibration would be such that a moon or satellite, revolving about the earth just far enough away to clear its surface, would exactly keep time with the os- cillations of this falling body. We Must Develop Nature's Gifts Owing to the increase in density of the earth as the center is approached, the force of gravity in deep borings in- creases at first as we descend. It has been computed that this increase would continue to a depth of about 900 miles, where it would reach a maxi- mum about 6 per cent in excess of its value at the surface. The key to success is an adequate knowledge of the world in which we live. The rise and fall of nations is dependent not so much upon the natural resources that they command as upon the genius they exhibit in making practical use of these resources. We see Russia and China, with all their natural wealth, lying fallow for cen- turies, because their inhabitants have not learned to seize, for the use of man, the wonderful opportunities lavished upon them by nature. We may have severe trials before us. Our staple source of energy will some day fail. But never, while the sun pours out its golden flood of light, can we complain of actual poverty. And the very earth beneath our feet, though her light died out in ages long gone by, still sends forth heat, repre- senting thousands of millions of horse- power, wasted upon empty space. The power is there. It is for us to make use of it.

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The two halves of the two sections of the buildings do not coincide. solves the elevator problem and stimulates the erection of tall garages Up Six Flights in a Garage N crowded cities like New York, where people live in apartment- houses and where there is not much room for individual garages, how can Space in cities is so costly that only a tall build- ing is practical for a garage, but the Ordi- you keep your automobile? use of elevators is undesirable. nary motor-ramps are too steep. Fernand E. d’Humy, an American found himself facing this problem when he moved from a subur- He a thoroughly Imagine a six-story engineer, ban home to a city apartment. devised and patented practical plan, This building built in two sections or units separated by a vertical parti- tion wall. The floors and ceilings of the two sections are not on a line, for the floor of one corresponds with a point midway between the floor and ceiling of the other. Thus an inclined passage from the floor of one unit to the floor of the other unit leads only half a story at a step, and the motor-cars can be run easily upgrade without too steep an incline. The motor- ramp can be arranged in the form of a curve, or it can be straight. Popular Science Monthly Hanging Electric Lights as You Do Pictures ITH a device patented by Cantelo White, a New York lighting expert, it is as easy to install electric-light fixtures as it is to hang pictures. With the new arrangement a tenant can remove a lighting fixture with the motion used in taking his hat off a hook. He may also place the same fixture in another part of the room in one or two seconds. A new kind of plug, with curved blades instead of the usual straight ones, and a new type of electric out- let to hold it, are the essentials of the new device. the ordinary baseboard receptacle. The two parallel slots that admit the curved-blade plugs are curved upward. will also accom- modate the stand- ard plug. The outlet is much like They With this invention lighting fixtures may be moved from one part of a room to another This Soldering-Torch Uses Two Fuels HE steady hand of a good me- ‘A. chanic is needed to apply sol- der. Many- people find this out after they make several attempts to mend the teapot or the wash- boiler. It is indeed aggravating to see the solder roll off in small balls as fast as it is applied. After a little experience, the would- be mechanic generally ends up by taking it for granted that soldering is a difficult job that only a mechanic can accomplish. An inventor has done a vreat service and filled a long-felt want by develop- ing a blow-torch that any one can use in soldering. No soldering copper is needed. The most inexperienced person can make solder stick with this little torch. The flameis applied directly to the piece to be soldered. Anybody can use this blow-torch to mend the family teapot or a favorite box; no soldering copper is needed 24 When it has reached the proper temperature—hot enough to melt the solder—the solder is brought in contact with it. Two separate compartments make up the torch. They contain different fuels. One fuel feeds the burner while theinflammable vapor of the other is blown into the flame. This is done with a little hose that the user blows through. A very hot flame is produced. The flame is hot enough to bring metal to a red heat. The little torch may be used for light brazing as well as soldering. Many household objects may be rescued from the family scrap-heap by the use of the little soldering- torch. Mother’s favorite kettle may be saved, also umbrellas and saucepans.

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rn Publishing Company Drawing by G. H “I Am Over Ashford,” Says This Airplane Automatic Wireless Until recently it has been necessary for an airplane to carry an operator for wireless in addition to the pilot. When the pilot wished to send a message, he first had to get it to the wireless man, who relayed it on to the world below. Now there has been perfected a device for sending wireless 25 messages automatically, and the pilot can do his own wireless- ing. He can do this without even knowing the code. This new automatic wireless transmitter will send any one of sixty radio messages by merely pulling a handle after inserting a plug in a hole labeled with the desired message Davis

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Popular Science Monthy April Looking at Dew through a Microscope. Courtesy of the Bray Studios In winter the dew often Mia oe OS raat K Mr. Bentley lives in Jeri- freezes as it forms, and the . ee ; aa cho, Vermont, and most of result is hoarfrost. When ie P > eel his photomicrographs were seen under the microscope, . / as si . taken there. He has two the frozen dewdrops are ™ ~~, ‘ Te thousand pictures of snow oblong and not globular in ; . ce oy “5 crystals and they are so shape. The picture shows N = . y am CS perfect they are often mis- a greatly enlarged black- t ; “> “im taken for drawings. This berry spray, the leaves out- : ihe: ~~, , § oe ' J picture shows dew on straw- lined in frozen dew ee wee M, \ berry leaves SAAR. WNW DH _ Ceo BE EE EO Wilson Alwyn Bentley knows more about dew, hoarfrost, snow crystals, and raindrops than almost any other man. This picture and the other ones on the page are but a few of the many hundreds he has taken of dew as seen under the microscope. ‘‘Dew on field grass’’ is the title of this picture eee we “Lcddcada eee daddiaedasadibddddsdliddlassste UMMM i El manent, > SSS S SSN S WK Ss Why is dew? Mr. Bent- ley says that dew is caused by the slowing down of the molecules of water in the air when the sun’s heat is withdrawn. This picture : ‘, shows dewdrops on the " — , , Ts sss ends of ‘“‘mare’s tail’’ grass Strings of pearls? That’s what they look like, but they are plain dewdrops clinging to a spider’s web. We always talk about dew falling, but Mr. Bentley says that it rises more than it falls. The earth, the plants themselves, and the air immediately around the plants, furnish the moisture that turns into dew In comparison with the stem in the picture above, the dewdrops look large enough to be_ apples. Perhaps their size is due to the fact that the stem field grass—is itself de- void of moisture

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Making a Plaster Cast from a Living Model © Keystone View Company A plaster cast must set for eight min- utes before it is re moved. The re moved cast is a negative. To make a positive that looks like a_ real face he pours plas ter into it. Rough spots are chiseled Miss Felyne Verbist, a away Belgian actress, is shown here preparing for her cast. She smears her face with vaseline to pre- vent the plaster from sticking. She must be particularly careful with her eyes and eyebrows Here they are, side by side. Unfortunately, when a cast is taken, the model must close the eyes, and also lie down. Asa re sult the cast always seems deathlike Z Somme Pierre de Zoette, the sculptor here at work, stretches a wire across Miss Verbist’s face down the middle. Af ter the plaster is set, this wire will be used for cutting the cast in half so that it can be removed

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What Does Mars Look Like? A mystery to be solved by other means than direct vision CROSS a broad river the dim A line of the opposite cliffs is seen through the blue haze. Scarcely any detail is discernible, because the atmospheric veil and the distance ob- literate the features of the ‘‘ultimate”’ surface. But, as the ferry approaches the opposite shore, gradually the con- spicuous features of rocky ledge and woodland are disclosed. Finally, as you step ashore and walk up the path leading along the side of the ledge, you see the kind of rock and the kind of shrubbery that from the distance ap- peared merely as an indistinguishable blur of colored shadings. To the naked eye the moon is but a shaded disk, a platter of silver or gold with gray shadings. An opera-glass discloses a definite shape in its light and dark markings. The features of the ‘‘man in the moon” turn out to be strongly marked dark spots; the white spots and streaks that are con- spicuous at the time of full moon are disclosed. The Limitations of Telescopes Now try a telescope with a mag- nification of 100 diameters, which means that one hundred naked-eye moons in a line would stretch across the magnified moon. No longer are the dark spots merely tinted patches. By Latimer J. Wilson They stand out, during the first or last quarter of the moon’s revolution, as flat plains. The white spots become elevations that cast black shadows. A great wealth of detail—indeed, too much to be grasped by the eye in a first view—is shown. When the magnification is increased to 500 diameters, the individual craters are brought so close that a depression marked with contrasts of light and shadow can be seen and measured when it is actually less than one mile in diameter. With a magnification of 1000 diameters applied to a giant telescope with excellent atmospheric conditions, less than half a mile can be measured on the moon. With existing telescopes and ideal steady “‘seeing,’’ a line on the moon of but 2000 feet in length can be observed. A wall fifteen or twenty feet high, casting a shadow at sunrise or sunset, could be seen on the moon if its length were consider- ably less than one quarter of a mile. But the best possible seeing would utterly fail to disclose the ultimate surface of the moon, something that geologists could study and identify. Look down the side of such a lunar range as the “Apennines.” This mountainous mass extends in a long, curving line of cliffs for a distance of some 480 miles. A few of its peaks are very high, some of them being csti- mated at more than 16,000 feet above the general level of the lunar ‘‘sea- floor.”” As the eye searches the range under the best ideal conditions of seeing, it takes in areas, say, 1000 ‘eet square. Mark off a section of the earth’s landscape 1000 feet square, and then go up in an airplane until you reduce that area to a mere povnt, and an idea can be obtained of the uiter impossibility of detecting the real character of the rock or soil, or in- dividual trees or houses, included in this point. Earth's Nearest Neighbor The moon is the earth’s closest neighbor in space. Magnified 2000 diameters, it can be seen as though its distance were but 240 miles. Imagine looking at the earth’s plowed fields from such a distance! Peer through the rarefied air of our lofty mountain- peaks across the open stretch of the landscape, and you can distinguish other peaks that are as far away. But how much detail can you hope to detect? A geologist standing upon one of the peaks of the Rockies, sweeping the circle of the horizon, would con- sider his eyesight very good if he were able to glimpse the faint form of a * “ fe $6 * . ey * : * P A >) es -. oe ‘ 5 3 * S Sate oe a : “et * i an = ae DE ‘ This is an enlarged photograph of the moon’s Apen true character of these remarkable mountains, some of whose peaks are higher than our Rocky mountains Wp eee d .* - ™ is tae i . nines. It shows how little can be perceived of the “oe Popular Science Monthly B April, 1 28 ————

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April, 1921 ping con- vere of a Mars and the Earth Side by Side If an observer could see the earth and Mars shining’ effectively than the thin atmosphere of Mars. But side by side, he would scarcely distinguish the resem- the white polar caps, the dark oceans, and the white blance between the two worlds. The dense atmos-_ cloud-areas of the earth would be distinguished. Mars phere of the earth would mask its markings more _ has yellow deserts instead of oceans

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peak 240 miles away. But would he attempt to form an idea of the kind of rock that composed the distant moun- tain when seen from so great a dis- tance? He would decide the character of the remote mountain, not by attempt- ing to see from the distance its in- dividual ledges and vegetable growth, but by comparing it with near- by mountains whose structure he could closely study. The served on Mars.. A band of. these curious markings -girds the planet’s southern temperate zone, extending far across the equator in certain longi- tudes, and connected in places with the borders of the polar caps. What is more reasonable than the idea that these areas on Mars are vegetation? If so, what kind of plant-growth flour- ishes there? As the earth’s winter merges into Popular Scvence Monihiy spring, its tint on the distant hillsides changes. The red-ocher of the tilled soil gradually is veiled with the e:rly tints of growing plants. A gauze vel of green delicately spreads across the blue-tinted hills of the distance, an: as the season advances the colors undergo a cycle of changes. Similar changes have been observed on the pl:net Mars. But what is the ultimate sur. face of the red-yellow planet across the ocean of space? man who wants to study the moon’s surface is compelled to resort to the same ex- pedient in deciphering the structure of the mountain- peaks, crater walls, and rifts upon the moon. But here a difficulty is encountered in the fact that the structures on the earth’s satellite do not closely resemble the forms that are found on the earth. We have no gigantic craters; nor have we circular plains like those seen on the moon. What Mars Is Like The planet Mars, seen in the telescope, bears a pecu- liar resemblance to the earth. Great hoods of snow end ice cover the earth at its polar regions; Mars, too, has polar caps. There are broad yel- low deserts on the earth; also on Mars, if the interpre- tation of the expanse of yellow-red that covers three fifths of the Martian Cisk is Difficulties to Overcom The mystery of Mars may never be solved by direct vision. A city twenty miles in diameter viewed from the distance of the earth would appear as a mere point. ll the life teeming in a spot twenty miles in diameter would appear to our eyes only as a barely distinguish- able dot of light or dark. Science must solve the mystery by other means than direct vision. The analysis of light ema- nating from stars so remote that their disks cannot be discerned has disclosed the life history of the stars. From the surfaces of the planets we receive but reflected sun- light. Photographs of the reflected light obtained in various wave-lengths, photographs in infra-red, ultra-violet, and examinations of the reflected correct. Areas of blue-green, composed of tints of delicate hue ranging from emerald to somber gray-green, are ob- How little can be seen of the real surface of the ground from an airplane flying a mile or higher Here are hazy patches that represent The actual surface above it! plowed fields and dense forests. cannot be studied light in the polariscope, may eventually give an idea of the ultimate reflecting sur- face. *, ? ‘ 7 x can see the 44 4 ‘ Va ANS \ ATR) ANN mA ‘ Se a BE ey Ai’ \' : ». ~ ve uN ~ AX \\ .\ A Bal a a »\!\ ‘ Ay A\ ’ va \\ t ach . But when the airman flies low, say five hundred feet-above the ground, he furrows of a plowed field very distinctly 30 T 1 much art cc of the mone} of bas will h learns steppe A s brush’ the in art ex the fa he exe or tes to det 4 Abc of th Faber X-ray of ay bety e those heart behin Pigme Hence Paint An resem

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ides led arly veil the eTEO ges “inet SUur- ‘TOSS may irect nifles | the ould All Spot neter eyes uish- the than ema- ‘mote t be e life From anets sun- ected 1rious hs in and lected may 2a of sur- — April, 1921 This is an X-ray photo- graph of the kneeling fig- ure, which clearly shows that the woman’s figure was painted in over that “The Crucifixion” was X-rayed to learn if the Dutchman Engelbrechtsen was It was thought that the kneeling figure in the right foreground had been added later responsible for some of its elements. of the monk An artist was thereupon engaged to erase the kneeling woman monk. the monk restored. taking the place of artistic opinion and restore the This picture shows the figure of Thus are X-rays Detecting Art “Fakes” with X-Rays No longer need we depend entirely on the guessing or intuition of the connoisseurs HERE is so much humbuggery in determining the period to which an old painting belongs, so much that is mere opinion, that the art collector—particularly a member of the canny variety that made their money by the common-sense method of basing judgment on hard facts— will heave a sigh of relief when he learns that the scientist has at last stepped in to help him. A scientist may know nothing of brushwork, style, ‘‘atmosphere,’’ and the intangibles that serve the so-called art expert; but he can at least collect the facts just as he collects them when he examines a bug under a microscope or tests a piece of steel in a machine to determine its tensile strength. Science Aids the Art Expert About two years before the outbreak of the Great War, a German, Dr. Faber, for the first time employed the X-rays to determine the authenticity of a painting. Differences in density between flesh and bone account for those X-ray photographs in which a heart is seen locked in a human breast behind ribs, or a bullet in a fleshy arm. Pigments vary similarly in density. Hence the X-rays can reveal layers of Paint lying below the outer surface. An X-ray photograph of a painting resenbles the original no more than an X-ray photograph of a human being resembles a personality. But it does reveal the hidden truth. It reveals, for example, the changes made by the master himself—the painting out of a hand, the modification of a landscape, the softening of a facial expression. It is just as if we had before us a play of Shakespeare’s with all the corrections and interlineations that were made before perfection was attained. A forger, even if he is as conscientious as Holbein, could never hope to mimic all the subtle changes that Holbein was accustomed to make, and least of all the manner in which they were made. With the aid of the X-rays, Dr. Faber succeeded in disclosing the modifications and_ restorations to which a seventeenth-century ‘‘Lucre- tia’’ had been subjected, and with an accuracy that could not be attained by one of those experts who goes into a kind of trance, with his head cocked on one side, only to state after long deliberation that perhaps the painting belongs to the seventeenth century and perhaps it does not. Faber’s method has latterly been employed with extraordinary success in England to verify the authenticity of a painting known as “The Cruci- fixion,’’ which was painted by a Dutch- man, Engelbrechtsen, who died in 1533. Dr. André Chéron, of Paris, has likewise turned on the X-rays to ex- 31 pose what lies beneath the outer sur- face of a painting. One picture by Van Ostade, of men drinking at a table, when submitted to the X-ray test, proved to be a fraud. What the X-Ray Exposes It had been painted over a study of dead birds. Another, called ‘The Royal Child,’”’ a supposed sixteenth- century work, now in the Louvre, proved to have been painted during the last century over a picture of very much earlier date. The old masters used paints that respond to the X-rays differently from those employed nowadays. The glazes of old masters, too, were different from ours; they do not react to X-rays quite in the same way as do our mod- ern glazes. If an art object can thus be tested as a chemist analyzes a substance whose name he does not know, the art expert will occupy a less exalted posi- tion than he now enjoys. Thescientist has no preconceived notions, no preju- dices. He works objectively for the truth. At best the judgment of an art connoisseur is a higher kind of guessing or intuition. By handling a painting as if it were a mysterious compound, the true nature of which is to be deter- mined, the scientist may be able to foil a forger.

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Popular Science Monthiy ae Ho’ R° “Tf t a exist Triangular Wheel Fram Bae: ex” the | filled belmeen floats, i a ie tinue in raised hosition F . child x. i G % StS Tis tS TERS x +. © Modern Publishing Company Drawing by S. W. Clatworthy Alighting on Water or on Land A SEAGULL draws up its feet when it flies or floats, but when it alights on land, its feet are very service- able. Thus flying-boats are equipped with wheels, so they can also run on the ground. When they drop upon the water, their wheels are drawn up and their boatlike bodies cut through the waves. But their efficiency as air-machines is ham- pered by the additional equipment, and ‘‘ amphibians ” are as yet not equal in some respects to seaplanes or to regular land machines. The recent British government competition for amphib- ians provided the first serious attempt to solve the problem of an airplane that can land upon either land or water. The three prize-winners, here shown, were the Vickers’ $50,000 Viking, the $40,000 Supermarine, both boat- seaplanes, and the Fairey, $10,000, a float-seaplane

Damalar Sar:onae BM nwt]...

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April, 1921 How Will Our Ten_Billion Descendants Live? ECENTLY Professor E. M. East R made this startling statement: “If the rate of increase in population existent in the United States during the nineteenth century should con- tinue, within the span of the grand- children of persons now living, the United States will contain more than a billion inhabitants.”’ There are in the world at present about seventeen hundred _ million people, with an annual increase of from fourteen to sixteen million. The white race is increasing much more rapidly than the yellow or the black, while China’s three hundred million is virtually stationary. Says Professor East: ‘‘The struggle for existence in those parts of the earth at present most densely populated will be beyond the imagination of us who live in a time of plenty.” Honeycombing the Radiator of Airplanes ELOW is shown a honeycomb type B of radiator selected for cooling airplane engines of large horsepower because of its great cooling efficiency. This efficiency is secured because the water is spread into thin sheets and made to pass between thin brass tubes, the ends of which are hexagon shaped and soldered together. Due to the narrow water passages between the tubes, the latter have a large area exposed to the cooling cur- rents of air through them. This large cooling area and the fact that heat is more easily extracted from a small stream of water than from a large one, give this radiator its great efficiency. The large cooling surface of this radi- ator is evidenced by the ability to dis- cern the face of the woman behind it {nrnl. 19971 One man, comiortably housed in a cab that is placed on a level with the extensible boom, operates this huge hoisting and transporting crane This Hoisting-Crane Saves Power EVERAL novel and practical fea- tures are embodied in a cargo crane and transporter recently devel- oped by Warren Travell, an engineer in New York. It is of the counter- balanced type, uses only one drum for the vertical hoisting and the horizontal traversing of loads, requires only one operator, and may be adapted to a variety of conditions that may be found at cargo docks. One of the most important features of this crane is that during the hoisting operation the entire weight of the bucket or skip and one half of the weight of the cargo load is balanced by a counterweight. The transporter beam, along which the load travels horizontally, is also balanced, and may be extended to suit existing conditions. When the boom is drawn in, the slack of the rope is taken up by the counter- weight. During the operation of lowering a load, the motor’s power is employed to raise the counterweight. Since the motor never has to carry the load itself, but only the shifting dif- ference between the weight 33 Another type of the same crane, with inclined boom, is shown here; it is oper- ated with a single drum of the counterweight and the load plus the weight of the skip or bucket, the lowering is safely accomplished without the use of a brake. The hoist-drum is rigidly keyed to its shaft, and ne friction clutch is required to control it. The crane rests on legs ending in rollers, one set of which runs on a track along the water-edge of the pier, the other set on a track on the roof of the freight-shed. On these tracks theen- tire structure may be moved along the water-front as desired. Hatches must be provided in the roof of the shed. EXTENSIBLE END » BOOM a ~ =e

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Fire-Stations Use Maps A DRNEAPOLIS has an almost per- +¥4 fect fire-signal system. Beside the telephone switchboard is an electric switchboard that controls a series of lights on a map of the city. These lights show the location of all stations. A green light represents a hose com- pany, a red light an engine company, a Popular Science Monthly white light with a black dot an auxiliary company, and a white light with black stripes a hook-and-ladder company. As these companies go out, the operator presses the control buttons and the lights flash on the map. Level Shelf for Boats F the man who owns a motor-boat wishes a level shelf in his boat, here is a bracket that will do it. It consists of an upright piece having a pin hinge at the top to hold the strip to which the shelf is fastened. The sup- port connecting the top of the bracket with the upright piece is in two sections, joined by a threaded boltlike member. To tilt the shelf up or down, this mem- ber is adjusted as needed. © Keystone View Company When the Chlorine-Tank Leaks (Aiea. gas kills germs immediately. That is why the cities use it to purify drinking-water. In fact, chlorine gas has no particular regard for human beings either, since it handles them just as roughly as germs. The first poison gas used by the Germans during the war was chlorine. When a high-pressure liquid chlorine- tank in a city pumping-station springs a leak, great care must be exercised in repair- ing it. One thousandth part of chlorine in the air will cause death upon very short ex- posure. The gas in these big tanks is in liquid form, and a high pressure is necessary to keep it in this state. Therefore leaks are apt to occur. The little pipes leading from the tanks seen in the picture above carry the deadly gas to the water. To Purify the Swimming-Pool UBLIC swimming pools should be sup- plied with water that. is constantly changing, but that remains at one tem- perature. This is not practical in ordinary cases, and, though we should prefer a fresh water bath, a substitute has to be employed. ‘ There are several systems by which this is accomplished. First,a strainer is used to remove large particles such as grit. Then it is necessary to sterilize the water. This can be done in several ways, either by ex- posure to the open air or by subjecting the water to the effects of ozone, and finally by the use of ultraviolet light. But it is essential thatthe water should also be filtered. 34 Measuring the Wind with Scales HIS is a balance upon which sliding or adjustable weights are used to measure the force of wind. When the air flows parallel to the direction of flight indicated by the posi- tion of the biplane in the picture above, the pressure of air upon the models’ sur- faces tends to disturb its balance. This produces a wabbling effect, which is registered by the support of the model, and can be counteracted by adjustment of the weights on the aerodynamical bal- ance. When properly adjusted, the model becomes stable in the flowing currents. Grooved Floor-Boards for Houses poet time you put down a new floor, 1 N you may so arrange the boards that the nails will be invisible. When ordinary matched lumber is used, the cracks open up through use and fill with dirt. This new way of matching floor-boards will overcome the objectionable features just mentioned. Each board has a V- shaped groove on one edge and a V-shaped tongue on the other, so the boards fit together snugly. a Ne RRR 4 = Or: Aw. NY - by wees a ¥ ~~ 2, * ia BE Unit T was batt of t] of t war dt ovel mol the B bits arti: repr cute fron

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uthly —. ales iding d to . the posi- Ove, sur- This *h is odel, ment | bal- nodel its. USES floor, that inary on up yards tures a \- aped is fit April, 1921 Shocking the Bicycle Thief A*™ electrical shocking apparatus for the man who tries to steal a bicycle is going to give the thief the surprise of his life when he takes his seat and attempts to ride away. He will experience a terrific surge of current through his arms, and he will be lucky if he does not find himself sprawling on the street. \ small induction coil is connected with the handle of the bicycle. When one sits on the seat, the circuit of the coil is closed and the device is thrown in opera- tion. When the owner of the bicyele wishes to ride, he opens the box containing the coil and breaks the circuit with a small switch. If he is absent-minded and forgets to do this, he will be reminded of the fact in no gentle man- ner when he attempts to ride off. Belleau Wood in Plaster ELLEAU WOOD, in France, will for- ever remain in the memory of the United States. The plaster-of-paris map shown below was made to keep the memory of this great battle alive and to enable army students of the future to study the military features of that famous engagement of the great war. The details of the landscape are placed over the plaster of paris, which is first molded to correspond geographically with the actual locality in France. By the use of paint, sponge for trees, and bits of wood and cement, the landscape artists brought into being this beautiful reproduction, which is so faithfully exe- cuted that it looks like a photograph taken from an airplane. 5) Keystone View Company .. > : ee | te OLS OALY One of Burma’s Religious Customs HE Burmese are fond of pagodas, by the erection of which they think they gain great merit, counting toward peace in the next world. They are also like chil- dren, fond of a joke, so they build their pagodas of queer and fantastic shapes. The framework is usually of bamboo covered with gold and silver paper, and the erec- tions are often put on rafts, supported by barrels, and floated in rivers or lakes. The illustration shows a_ particularly gorgeous paper pagoda, intended to repre- sent a curious kind of hen, floating on the lake at Meiktila, in upper Burma. Cook Pork Thoroughly N°? matter how healthy the animal, un- cooked pork probably contains live trichine. Pork products that are prepared in establishments operated under federal supervision are subjected to processes that destroy the parasite. In the home the same end can be attained by making sure that the meat is thoroughly cooked, when it is more or less white in aspect, even at the center of the piece. Keep Your Horses from Slipping OR humane reasons, horses employed to pull heavy trucks over the ice-covered pavements of city streets in the winter should be equipped with properly fitting ice shoes or creepers that will keep them from slipping and protect them from falling and possible injury. The anti-slipping shoe shown in the accompanying illustration is a French invention. It consists of a steel plate shaped to fit the hoof, and provided with rivets, the heads of which prevent the horse from slipping. The steel plates are padded and are at- tached to the hoofs by hinged clasps and buckle-straps of leather. The creepers are easily re- moved when not needed and do not materially injure the _Yroad surface, even when they are used on a thin sheet of ice covering. He Keeps His Car in a Tree ( ARAGES don’t grow—they are built. Yet there is one garage, located near Santa Cruz, California, that was made absolutely by nature. It will accommo- date one large car. How did it happen? About a thousand years ago a tree started to grow. It con- tinued to grow on through the centuries, and, at some remote date, caught fire. The fire consumed a large part of the tree-trunk, and, when it died out, left a great hole in the bottom of the trunk. The man who owns the property on which the tree stands now stores his car in the tree. This garage has one advantage that a number of other garages lack—it is in entire accord with the surrounding landscape. © Keystone View Company

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Popular Science Monthli, Horses Live in this Hotel = OBBIN’S in room 402,” says the hotel clerk to the manager. What’s he doing there? you wonder; for “Dobbin” is certainly the name of a horse, and horses are not usually found in hotel rooms. But the hotel in question is a horse hotel—all four floors are divided into stall- like rooms, and there is a long, sloping runway at the back. The horses use this runway in going to and from their rooms. What’s the idea of it? The man who owns the hotel owns the horses, and also owns several carriages. He _ believes, wisely, that if he treats his horses well, they will look well when hitched up. He does a thriving livery business in Berlin. Certified Water N ILK is “certified,”’ which means that it can be drunk without danger of con- tracting typhoid. Why not certify water? After all, water is more freely drunk than milk and is more likely to be contaminated. Accordingly, the Public Health Service co- operates with the different State boards of health to test the water used on railway- trains and boats for drinking and for cooking. This will tend to curb the severe outbreaks of typhoid fever that originate in ships and railway-trains. Ten Million Years Old Is this Footprint A Burn Can Be Dressed with Egg-Skin TOT only is an egg one of the most 4‘ valuable foods in the sickroom, but, like many patent medicines, less worthy, but more widely advertised, it can be applied externally as well as taken in- ternally. Reliable medical authorities have recom- mended the thin skin of an egg as an ex- cellent dressing for burns and cuts. The thin film that is just inside of the shell is already sterile if one’s hands do not touch its inner surface before applying it to the wound. The skin adheres to the wound itself, and not only does it keep out the air, but it accelerates contraction and quickens the process of healing. Try it the next time you need to dress a burn, and you will find how well it works. Up Goes the ‘‘Drawbridge’’ ERE is an unusual bridge that lifts itself in the air when it is necessary for a boat with high masts to pass under- neath it. A powerful lifting-hoist is located at the top of the bridge. A cable passes through the center of each of the steel posts. The bridge is lifted from all the four corners to the top of the structure, exactly as an elevator rises. When in this position, traffic may pass without hindrance. The bridge drops back into place. Where do you think this typically mod- ern bridge is to be found? You will be surprised to learn that it is in the city of Manila, Philippine Islands. Protecting a City with Dummies CURIOUS fact has just come to light concerning a plan to protect Paris from air raids during the last days of the war. A complete imitation of the Gare d’Est, with about two miles of railway lines, signals, sheds, and trains, was constructed about fifteen miles from the French capital. Translucent canvas, with dummy trains, was laid on the ground, and the steam and smoke of factories was _ imi- tated. Searchlights and half-hidden lamps formed the night illumination of the imi- tation city of Paris. You Are Met at the Door by this Mud Brush EN million years agoa great dinosaur, weighing many tons, trod on this spot. The spot was soft clay at the time, but as the centuries rolled by the clay became hard and _ stone- like. The impression to-day is nearly as distinct as the day it was made, millions of years ago. The two great toes of the beast left clear-cut marks, which may be seen in the photograph. These footprints were recently discovered in Connecticut, and scientists attach great impor- tance to the find. The footprint shown in this picture is not the only one, but it was the best preserved. ITH all his faults, . the average German” is cer- tainly very neat.” And-his wife is properly called a Hausfrau. She spends all her time in the various branches of keeping house. Dirt and dust and mud are her enemies. In many German homes to- day you will find a long-handled brush, like the one at the left, standing just inside the front door. The brush is shaped like a mound, and the bristles radiate from the center. What’s it used for? Cleaning shoes before entering the house. Its shape enables the user ‘to remove mud from any part of the shoe. strum Altho only ) used t group The and | comes in apf cTOSS k Keer H) m¢ at th nolog’ hund Fac slot. use, a spond will te body The institi in the © Bostc

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LR 008 RS ign “he to an on, “he od- be of ies pht om yar. ist, 1es, ted nch my the nps mi- the rer- vife au. the ing nud to- led eft, ‘ont like late ing use. to . of April, 1921 “‘Camera!’’ Shouts the Director AT last a way has been devised to allow a motion-picture director to conduct a large scene without shouting at the top of his voice. The loud-speaking telephone is the in- strument that has made this possible. Although it is not a new invention, it is only recently that this device has been used to carry a director’s voice to a large group of players on location. The director speaks into a mouthpiece, and his voice, many times magnified, comes from a horn. The instrument, both in appearance and working principle, is a cross between a telephone and a phonograph. The Prophet’s Traveling Tent ENEATH a canopy of gorgeous Orien- tal rugs that protect him from the sun, the prophet of Mohammed moves across the desert. In this sacred seclusion he prays with much ceremony until the time arrives for him to step out before the multitude. Four thousand years ago temple altars were oriented to the rays of the splendid Sirius and other stars. But today the gods are no longer in evidence except in the temple ruins. In their place the mod- ern religions hold sway, and every sunrise and sunset sees the long-robed Arabs kneel- Keeping ‘‘Tabs’’ on School Classes ing toward Mecca, bending low in prayer. HIS class record-board looks like a mosaic floor at first glance. It is in use at the Massachusetts Institute of Tech- nology to keep a record of the use of the one hundred class-rooms and auditoriums. Each eclass-room is given a number and a slot. When this or that class-room is in use, a small card is placed in the corre- sponding slot on the record-board. This will tell at a glance just where every student body is at any time of the day. The exact location of any student in the institute is also known, a precaution taken in the event of an emergency. © Boston Photo News Company Coffee-Drinkers on the Increase VER $300,000,000 worth of coffee was imported into the United States last year, according to the statement issued by the National City Bank of New York City. As the preparation of this material for the market, including roasting, freight, and distribution, must be added, the total valu- ation amounts to about $365,000,000. Maybe prohibition is responsible for the increase in coffee-drinkers. At any rate, they drink $1,000,000 worth a day. How Big Bells joa Tine. ERTAINLY this will look like tuning-machine to you. But machine it is, nevertheless. It is used only in tuning large bronze bells. In this case, it is tuning one of the bells to be used on the Royal Exchange in London, England. The bell is mounted on a boring-mill to have some of the metal on the inside turned off. A boring-mill is a vertical lathe for metal turning. As the metal is cut away from the interior of the bell, its tone will be changed. The cutting is continued until the bell just the tone desired by its a queer a tuning- possesses makers. Shaken Up in a ‘‘Movie’’ Box NTO an empty box on the station plat- form jump the frightened bride and groom. The bride’s furious father appears. The baggage-men bounce the box down the platform. Of course, you are sure the bride and groom are not in the box when this is done, yet a close-up shows them whirling in it. The picture below shows how this kind of close-up is taken. The box, with the bride and groom wedged in it, is placed in a cylindrical case. The case rests on rollers. Both background and case are black. The case turns smoothly on the rollers. iii : tft. [ wes elit, Seatenttatee ly sia : pt th yyy rad abel —_—_—_—. =

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Longer Life for Shoes N ETAL tips and heel plates will pro- long the life of a pair of shoes, but at the same time they will scrape all the varnish off the floors on which they travel. How can this shoe problem be settled satisfactorily? The steel disk shown on the shoe in the picture above is one solution. It is countersunk in the tip of the shoe, and consequently does not strike the floor before the surrounding leather. Pellagra’s Relation to Poverty ONCLUDING a three-year study in cotton-mill districts of South Carolina, the U. S. Public Health Service has come to the conclusion that the prevalence of pellagra varies inversely ‘with the family income. This is the first reported con- firmation of the suspected relation between poverty and pellagra. As the income falls the disease affects more of the family: with higher incomes it affects fewer. A One-Truck Train ERE’S a whole railroad train, ‘Train Number One,” on the Elkin and Allegheny Railway, which isn’t a train at all, but just a Ford truck equipped with flanged wheels, enclosed body, and trailer, the latter serving as the baggage-car. This improvised passenger-coach oper- ates over a roadbed at the foot of the Blue Ridge mountains, for a distance of sixteen and one half miles. The car seats nineteen passengers and a driver. On one of “Number One’s”’ trips last win- ter, running over a wet track, it carried twenty-nine passengers, 1187 pounds of mail, and .940 pounds of: express—totaling, approximately, 6150 pounds—up a two and one half per cent grade on high speed. Cooking the Meat for the Animals in the Zoo AT meat but once a day—that’s what the doctor tells you. This schedule is followed in zoos, and the amount of illness among the animals is usually surprisingly low; undoubtedly the fact that they are not allowed to eat meat more than once a day accounts to some extent for their -general good health. The four-footed animals are given plenty of vegetables and bread—in fact, they eat the same kind cf food that we eat, but in greater quantity, of course. In the picture above you see one of the large modern ovens now in use in Bronx park—New York’s mammoth zoo. Huge pieces of chuck are broiled every day and fed to the smaller animals. Monkeys and bears like their megt cooked, while all the members cf the cat family—lions and tigers, for example—like their meat red and raw. The very old and the very young ani- mals are given the more tender parts of the meat; however, meat is so expensive nowa- days that only the cheaper cuts can be bought and therefore not much discrimi- nation can be shown. Popular Science Monthly Casing the Cigarette-Holder N° so long ago silver chatelaines were very popular among the women. From them hung anything small and silver. The same thing is now happening to men’s watch-chains. And one of the latest hangers-on is the cigarette-holder case shown above. The case is small and golden; the cigarette-holder is collapsible and fits snugly inside the case. When you are not smoking, you wear the case on your watch-chain. Sawmill Waste as Boiler Fuel N ILLIONS of tons of sawdust are thrown - away inthis country yearly. It isonly recently that serious efforts have been made to use this materia]. Sawdust burns slowly, witha fair production of heat, and produces little ash. A number of sawmills throughout the country are attempting to get rid of this waste material by using it in place of coal as far as possible. Threshing Planks into Shreds ““TSHRESHING-MACHINE” was the sign outside of one of the lots at a county fair. Yet the men within were feeding the machine heavy oak planks! All the farmers gathered around. That was exactly what the exhibitors wanted. They wished to demonstrate to possible users the strength of the thresher teeth. The planks were fed into one end of the machine and came out in shreds at the other end. ‘D' cal ion ing fe ployir the ni be he gas fl up pl for 1 It we trode so th: revol form is ple It T M more by t are equi load T tain and gaso larg spit load thor tage

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Vn ly de ly, "eS he his yal he re cS! rs to he he April, 1921 Welding as It Revolves “1° it by welding’? seems to be the modern idea. The commercial appli- cation of gas and electric welding is grow- ing fast, indeed. Manufacturers are em- ploying this system more and more. Where the noise of the rivetting hammer used to be heard, the hissing of the electric arc or gas flame is now evident. Welding speeds up production. Here is an electric welder for welding steel barrel heads in place. It welds as the barrel turns. Three elec- trodes come in contact with the barrel head so that the barrel only turns one third of a revolution. The high-amperage _ trans- former which furnishes the heavy current is placed at the top of the machine. It Takes the Place of Thirty Men y, queestrsge by a crew of three, this motor-crane is capable of setting more telegraph-poles than could be handled by three gangs of men. Similar economies are realized by using the motor-crane equipped with a clamshell bucket for un- loading bulk material from freight-cars. The crane is a full-swinging, self-con- tained type, rotating through 360 degrees, and is driven by a separate four-cylinder gasoline motor that is built with an extra large flywheel so as to run smoothly in spite of sudden application and release of loads. The capacity cf the crane is eight thousan’! »ounds, and its particular advan- tage x tnat tt moves rapidly. How Miners Charge Their Lamp Batteries ANY of the miners’ oil-burning lamps have given way to the safe electric light supplied with current by a small stor- age battery. When the miner starts out on his day’s work, he takes with him a freshly charged battery. The charging of these batteries used to be a haphazard matter, but, like everything else, it has been systematized. A new charging-rack did the trick. When the miner comes up to the surface after his day’s work, he places his battery in the rack under a certain number. When the battery is slipped in place, it is auto- matically connected with a charging cir- cuit. The miner returns the next morning and finds his battery fully charged and ready for another day’s work. When Lying Hurts the Liar HE most misunderstood form of lying is that known as ‘‘mythomania.” In it the person who tells the falsehood does so without purpose, and sometimes with injury to himself. It develops from the fable-emaking of childhood, and, unless corrected early, will work great harm in one’s life. There have been cases of mythomania in adults that have baffled the best detectives. The victim has told things about himself that might be highly incriminating, and when questioned made use of his quick presence of mind to strengthen the circum- stantial evidence against himself. This mental disease often works harm upon others who are as innocent as the mythomaniac himself, though he is as prone to tell flattering lies of himself. ey a _—__ —_ 4 Clesing Bags by Machinery ECAUSE one machine can close as many large bags of sugar, feed, seed, rice, etc., as can be sewn by four men, bag- closing machines are rapidly taking their rightful place. The portable, electrically driven bag-closing machine shown in the accompanying illustration is a recent development. Besides being quicker than hand labor, the machine does the work cheaper and better. The better work performed by the ma- chine as compared with hand methods, is secured by sewing the mouth of the bags with eight stitches to the inch instead of three or four as by hand. This close stitching has saved thousands of dollars. First Aid to Horses HEN Dobbin falls in a hole or drops over an embankment, a hurry-up call is put in for the horse ambulance and derrick-car shown below. Ropes are thrown around the body of the animal, and it is hoisted up to the ambulance trailer and carted away to its stall or to a horse hospital. The derrick, although operated by hand with the aid of a small winch, is easily capable of lifting a heavy truck-horse. Any tool that may be needed in extricating the animal is carried on a board at the side of the motor-truck. It will be noticed that the ambulance trailer is a two-wheeled model. © Keystone View Company

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Every Dog Has His Day— Sometimes in the Hospital An elaborate veterinary college for pets is maintained in Berlin \

Here you see a puny pig that will never become pork unless he can be treated by an ex- pert veterinarian. What the woman has in her bundle is a matter of conjec- ture

tee te This hen moped around the yard. She was taken to the Berlin Veter- inary College and two experts look her over tho roughly Nea A very slight operation is

Popular Science Monthl;

necessary in the case of this dog; thus, instead of chloro- forming him, the doctor has strapped a mask over his face. If he can’t see what’s going on, he won’t become nervous This dog sneezed, coughed, and had a hot nose—his master rushed him to the hospital. The doctor listened to the beating of the dog’s heart and was able to tell what ailed him

| & * Sf < ~ ah DA. : \ Fourteen of them—all waiting for the doctor to treat their ailing pets. hens, and pigs are the most frequent patients, and they all receive the best of care

Dogs, cats,

40

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hly Apri, 1921 How Would You Meet These Tests? Discovering what particular job in the world you are best fitted for Photographs © Keystone View Company **Am I musical?” you ask. The psychologist has found that | there are at least eighty factors that determine musical talent. One investigator has fixed five of these eighty factors. They include acuteness of hearing, ap- preciation of pitch, time, etc. By listening to a metronome (as this boy is doing), the sense of thythm can be tested The housesmith who rivets and fits steel beams on the frame of a skyscraper must be steady on his feet. Stand on one foot and test your steadiness. It is not easy. You sway after atime. It was thought a few years ago that such tests, conducted in a lab- oratory, would reveal a man’s fitness to hold a certain job. Psychologists now find that the problem is not so easily solved On the table is a metronome—a time-beater. The seated man taps with a lead-pencil in time with the ticking metronome. The examiner, watch in hand, notes how accurately the sub- ject taps. Thus muscular con- trol of a certain kind is tested Can you touch the bull’s-eye with a pencil? This Something is missing in the objects pictured. It is is called the “aiming test.” It doesn’t follow that atest of attention, alertness, and analytical ability a man who can’t touch the bull’s-eye every time is to discover what is wrong in a given time. A man . so defective that he cannot fill a specified job. The who fails in the test would not make a good loco- test may prove him only 62 per cent proficient, but motive engineer, detective, botanist, or druggist ; he ia in his work his percentage may be 190 could not fill a job requiring accurate observation 41

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Radio now comes to the aid of the business man. This progressive German broker has found a new use for it Brokers Find a Use for Radio A NEW use has been found for radio. Up-to-date brokers are now using small radio outfits to keep iheir clients informed regarding market fluctuations. A small but powerful transmitter is installed in the broker’s office, and his clients are provided with a sensi- tive receiver. The aerial used is of the “‘loop” type, and it is so small that it may be placed on the desk in the office. The stock reports are sent out at regular intervals by this radio ‘‘ticker.”” Such installation is inexpensive and costs very little to operate. It is fairly safe to assume that this method of communication will soon become universal. Popular Science Monthly No Disturbing Noises ID you ever try to carry on a telephone conversation when the wires were sizzling and crackling? “Hello!” —snap, crack—‘‘Hello? Yes, as I—” Bang! A new telephone has been developed that is immune fron the ordinary disturbances that make hearing difficult The diaphragm—that little disk of thin metal that receive: the sound impulses produced by the voice—is so arranged in the transmitter that any disturbing noises will strik: both sides simultaneously. If both sides of the diaphragm are struck at the sam instant, with equal force, no effect will be produced, and th: diaphragm will not vibrate. The sound impulses from the voice strike the dia- phragm from one side only, and they are im- pressed upon the circuit. This in- strument will operate without interference in a room with several aviation engines going. This will make it of great value for intercommunica- tion on airplanes and large the engines is so loud. Conversation may be heard over this telephone with a vessels, where the roar of umber of Liberty motors operating in the same room The Truck with Almost Human Arms ECAUSE it will mechanically load and unload wagons, mo- tor-trucks, or freight-cars, and pile or tier the material in stock- rooms where cranes are not avail- able, the new industrial truck here shown appears to have almost human arms. To be sure, these arms are made of metal, and are much stronger than human arms, since they will lift a maximum of two tons from twelve to seventy- six inches from the floor or ground without rehandling. But, even more than that, the truck will carry the goods from the point at which they are unloaded to the ae point where they are to be stored, 4 combination and will place the separate pieces ‘TUCK. and tiering- an p p p machine, consisting of the load one on top of the of a four-wheeled other—all without being lifted or framework on moved by a human hand. which is mounted a Because this work is done me- page he nidare ecause a vertical elevator chanically instead of manually, much time is saved, and the same work can be done with fewer men —both important factors. Be- cause the machine is capable of tiering the goods carried, either directly on top of a pile or on platforms, much valuable floor The platform is op- space may be saved through mak- erated by a motor. ing higher piles. Unlike human Goods can be raised arms, however, those of the ma- = t® 4 motor-truck or , ; stored on floors chine do not become fatigued as = yhere cranes are the day proceeds, so that none of not available their efficiency is lost. The ap- paratus is really a combination electric industrial truck and a tiering machine. It consists of a small four-wheeled framework on which is mounted a storage bat- tery and a vertical elevator. The powerful lifting arms are in the form of a horizontal plat- form that is raised and lowered by a separate motor placed on top of the vertical framework. The maximum load of four thousand pounds may be lifted at the rate of one foot in eighteen seconds. This is equivalent to raising the load forty-two inches from the floor in forty-six and one half seconds, or seventy-six inches in one minute thirty-seven and one half seconds. This speedy elevation has been made pos- sible by the development of a new worm and worm-wheel drive between the motor and the lifting framework. Because all four of the rubber- tired wheels are made to steer, the truck, one hundred and twenty-one inches in length over all, turns in a radius of ninety-two inches, or less than its own length. The storage battery is placed above the frame at the rear, and covered with a metal box. A pril, f H. Va manu a mar at | There never he do but s But side t His fr him | know them an 01 goods a satii at « that - an ex that— will g for dil some tying, for th He: exper maste Pri Trout A sti to be angle} must After tie dr winge that t Fiv becan comm them he su manu able flies te Can v: to thi weeks | Sects. winge alight back collec’ | them The room throw sit do provic tools,

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tion lo!” rom ult ives ged rike ame the - ap- ation id a ,of a k on bat- S are plat- vered n top The isand 1 rate onds. y the 1 the » half hes in and reedy pos- of a wheel * and bber- steer, and ength us of than orage 2 the vered April, 1921 Luring the Wily Trout Outside of business hours Leo H. Vaughan spends all his time practising the science of dry-fly tying By Raymonde G. Doyle export district, where he attends to business six days a week, Leo H. Vaughan, representative of a rubber manufacturing company, is known as a man who has the art of salesmanship at his _finger-tips. There are those who never would suspect he does anything else but sell rubber. But there is another side to this salesman. His friends like to see him coming. They know he will steer them along the lane to an order for rubber goods, but they grin in a satisfied sort of way at the recollection that Mr. Vaughan is an expert angler and that—well, maybe he will go up to the club for dinner and whisper some of the secrets of dry-fly § ee the New York A fisherman ever since he could bend a pin, and a dry-fly fisher- man since he discovered the fascination of the art, Leo H. Vaughan, a New York rubber salesman, spends all his leisure imitating the winged and unwinged insects that fishes feed on swiftly. He places one of the hooks in the vise, its shank horizontal and the point where it can do no harm. Next he fills the mirror-bottomed tumbler with clear water, and places one of the live insects that he is to imitate in feathers and silk on the surface. The mir- ror reflects the under side of the insect— the side the fish sees when he is searching for food. Great care must be taken to imi- tate the under side faithfully, is one of Mr. Vaughan’s discov- eries. He examines his model with the aid of the microscope. His fingers deftly twist a bit of thread around’ _ the steel shank. He has se- lected a color that shows in the _ insect reflected in the tumbler, and tying, and even tie one or two for their edification. Heis a practical entomologist, expert trout-angler, and past master at tying flies. Practical entomologist? Trout-angler? Dry-fly tyer? A strange combination! But to be a really expert trout- angler, Mr. Vaughan holds, one must first be an entomologist. After that he must. be able to tie dry flies—imitations of the winged and unwinged insects that the fishes feed on. Five years ago, Mr. Vaughan became dissatisfied with the as he works the body quickly takes shape. The natural bug may boast a rib or two of gold or silver, and these are imitated with fine wire. Then the wings—delicate bits of feather from one of the boxes —are selected and fastened to the body with a few turns of thread. The legs are formed from the hackle feathers of cer- tain birds. They are selected for color and texture, and as they must keep the fly afloat, they must be more numerous than those of the live insect. The thread commercial dry fly. Most of them came from England, and he suspected that the British manufacturers gave consider- ° able attention to their local flies to the neglect of the Ameri- can varieties. So he hiked out to the country, and spent days and weeks studying flying and crawling in- sects. He used binoculars on the Winged creatures to see how they alighted on the water. He brought back to his home in Brooklyn large collections of live bugs and studied them further. The Vaughan home now has a work- toom where the rubber salesman can throw aside his business clothes and sit down at a bench and a small table Provided with an odd assortment of tools, among them a watchmakers’ On the table in his workroom are all manner of curious tools—a watchmakers’ vise, a tumbler with a mirror at the bot- tom, feathers of the American wood duck and the Chinese mandarin duck, besides tiny scissors, forceps, and a microscope vise, a microscope, a tumbler with a mirror for a bottom, tiny forceps and tinier scissors, wax, and _ varnish. Boxes on shelves near by contain quantities of feathers of the American wood duck and the Chinese mandarin duck, both now on the ‘“‘thou shalt not kill” list; hanks of peacock herl, the outgrowth on the breast of the bird; feathers from the commoner birds, spools of vari-colored silk and wool and cotton thread, and boxes of small fish-hooks. At fly-tying Mr. Vaughan works 43 is knotted tightly at the head end of the fly and a drop of varnish is placed on the knot. The thread was waxed before the job was begun. Mr. Vaughan’s fingers now smooth back the wings or lift them to a saucy angle, according to the position of those on the model. The legs are clipped to the correct length and the job is finished. The fly that has been turned out ready to be fastened to a gut leader and cast over a favorite pool may be an imitation of the May fly—the white miller, as it is listed by anglers; it may be a black gnat, or the white miller’s little sister, the white moth. What- ever it is, it is an impudent-looking mite that could be a museum piece instead of a trout lure.

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L’opular Science Monthly

April, C On to HA S thi sus of our | can pre perior wing tl which | stiff, ris

A triplane glider in flight with Richter-Hauenstein, of Berlin, as pilot. Great efforts are at present being made in the direction of motorless gliders and lower- power airplanes

Eagles ahd vultures have been ob served to fly without the slightest apparent motion of their outspread wings. Clearly, they know how to use the fluctuations in air currents. Can man do the same? Must he always fly with the aid of engines that generate from fifty to two hundred horsepower? The problem of engineless flight has been attacked by a few bold experimenters in Germany. Like Lilienthal of old, they use what are known asgliders—machines built like airplanes, but engineless. A man runs with the machine down-hill or gets a start in some other way Here is a monoplane without an engine. The pilot runs down a hill or leaps off the edge of a precipice and then glides until the machine slowly drops

Many a mishap attends the engineless airplane. Lilienthal was killed in making a glide and so was von Loesel, recently. This is Drude’s machine after a landing

Some of the gliders in a contest held in Germany were very beautiful. In the air they were as graceful as birds. This shows Neesemann in a Zeise machine

To a inclinat gineer | pilot ha The bil few mi bones, wonder ; cording angle o If le muscles a sudde Pwing; | inclinat pressur' i flexes lessly. But i can at only fo are gres in the < © even if | to dete + Your » for inst: or neal deflect rushes | sudden! directio at this The gu ago, lo lengthy ® and the ® rent, er = ing dow a parti I visible. How © an alba = and fo = ertion, © sionally By b wing 8) § Spectah b elevate instane the alb: | The brother t before 4 biplane 05

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| April, 1921 Can We Fly without Engines? Only when we can produce a wing structure equal to the one that nature has designed for the birds By C. A. Oldroyd through the air like the birds, sustaining ourselves by the power of our hands and feet? Not unless we can produce a wing equal or even su- perior to the wonderfully designed wing that nature gave to the birds, which is far more efficient than the stiff, rigid surfaces of our airplanes. To alter the tilt, or the ‘‘angle of inclination,’ as the aeronautical en- gineer says, of an airplane wing, the pilot has to incline the whole machine. The bird alters only the tension in a few muscles, the position of a few bones, and gently the whole of the wonderfully flexible wing warps ac- cordingly, increasing or decreasing the angle of inclination. If less span is required, the wing muscles are tensed, the span decreased, a sudden gust can not harm the bird’s wing; it can, at the most, change the inclination a little. As soon as the pressure becomes too great, the wing flexes and lets the wind pass harm- lessly. But if we cannot fly like the birds, we can at least glide just as they do, if only for short distances. In this we are greatly helped by the disturbances in the air. These are always present, even if our senses are not fine enough to detect them. You will have observed gulls soaring, for instance, preferably near a sea-wall or near any obstruction that might deflect the air current. The wind rushes over the surface of the sea, and suddenly hits the sea-wall. The direction is immediately changed, and at this point the wind blows upward. The gulls have found that out long ago, long before the scientists wrote lengthy volumes on “natural flight’’; and they soar upon this vertical cur- rent, enjoying themselves hugely, div- ing down to the surface of the sea when a particularly tempting fish becomes visible. How can we do likewise? We watch an albatross following a ship for hours and for days, seemingly without. ex- ertion, only flapping its wings occa- sionally, By building a very light, airplanelike wing system, we can cover very re- spectable distances by gliding from an elevated point—the top of a hill, for Instance; but we can not yet sail, like the albatross, for hours on end. The inventors of the airplane, the brothers Wright, were expert gliders before they installed an engine in their biplane-glider, and they carried out G thro we ever be able to sail Sea-gulls take advantage of the air currents that are deflected upward as the wind blows against a cliff Sameer ars. a hundreds of glides. As soon as the air- plane developed, more speed was de- manded, and yet more speed. Heavier wings and sturdier fuselages were required to lift and support the more powerful engines; more fuel had to be carried, until, at the end of the war, we had the most uneconomical type of air- plane, equipped with a three-hundred- horsepower engine and lifting just one pilot. This was the fighting plane, which loops: and stunts, spitting machine- gun fire from the air. Its safety lay in its speed. It was equally diffi- cult .to hit from the ground and from another swiftly moving airplane. Peace time demands a different ma- ARI chine, an airplane that will carry a great weight with great safety at a moderate speed. Some aeronautical engineers have gone back to the glider to study gliding first and low-power flight afterward. Great efforts are being made in Germany to bring out an efficient glider and later a low- power airplane, as gasoline is very dear and the supply uncertain. A meeting of glider constructors was held at the “‘Wasserkuppe,” a hill that offers great opportunities for long-distance gliding. Hans Richter, an enthusiastic German glider, is here shown 1) tne au. After running down-hill, he draws himself up into the machine 45

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Daylight Saving for Plants Speeding up growth by controlling exposure By M. De Witt Pearl WO investigators, Dr. W. W. Gar- ner and H. A. Allard, of the Bureau of Plant Industry at Washington, find that the length of the day is of the ut- most importance in determining when a plant shall fulfill its primary func- tion—reproduction. This does not mean that heat or cold, intense or dim light, have no influence upon plant development, but simply that a plant is profoundly affected by the length of time it receives light. After some preliminary experiments, a large ‘‘dark house’”’ was constructed which, although allowing of free cir- culation of air, excluded all light. At no time was the temperature in the house enough higher to account for the results obtained. The experiments usually began with the seedling stage. Always control ex- periments were conducted at the same time. That is, and goldenrod. Beans, which under normal conditions in the regions about Washington blossom one hun- dred and nine days after germina- tion, would, when their daily supply of light was reduced to seven hours, blossom in twenty-eight days, and a month later produce mature seeds. Maryland mammoth tobacco, which can never be made to produce seed during the summer when grown by the ordinary out-of-door method, would, under the influence of a shortened day of seven hours, form seed-pods by the fourth of August. Ragweed also performs its best work on a short-day basis. On the other hand, hibiscus, cabbage, and carrot reach maturity more rapidly on a long-day basis. Another interesting result obtained Popular Science Moni), Soy-beans require a short day and a | night. The plants on the left were exposed to light five hours daily from May 20 till June 16, when the first blossoms appea: The plants on the right, exposed to day- light all day, grew luxuriantly, but did not flower until September 4 in juggling the amount of daylight that the plants received was the transfor- mation of certain species from annuals into biennials, the with the germination of the seeds of the type to be studied, some were placed in trucks to be run into or out of the dark house, according as the length of day was to be shortened or lengthened. In other trucks were placed the remainder of the seedlings, and these received precisely the same treatment, except that they were the recipi- ents of normal sunlight. The time of exposure to daylight for the experimental plants was twelve, seven, and five hours. The plants used in the experiments were several va- rieties of soy-beans, aster, entire process being complet- ed in these cases in a few months instead of two years. Soy-beans, brought quickly to the flowering stage in the early summer by a shortened day, were then subjected to a period of lengthened day- light. The result was that the seeds ripened quickly, the leaves turned yellow, and the plants gave every ap- pearance of following the normal course that such plants follow under normal conditions of blossoming in the fall. However, these plants that had been brought to an early maturity soon put out fresh shoots, which in violet, radish, ragweed, hemp- weed, beans, carrots, lettuce, hibiscus, tobacco, cabbage, Dr. W. W. Garner and H. A. Allard, of the Bu- reau of Plant Industry at Washington, find the length of day an important factor in plant life turn produced blossoms while the plants were still bearing the first crop of seeds. A Folding Cot for Home and Hospital _——_ NLESS the present housing diffi- culty is remedied in the near fu- ture, millions in this country may be compelled to sleep in cots instead of wooden or metal beds. In Germany, where the shortage of housing space is equally acute, a new type of cot is finding favor. The cot is light and easily unfolded and folded. When folded up, it occupies but little space and may be stowed away in a closet to be set up again in any con- venient place for use as a resting-place at night. Even where the shortage of ac- commodations is not excessive, it is convenient to have one or more of these cots on hand in case of emer- gency, for instance, where unexpected visitors spend a night at one’s house. It looks very comfortable made up. A number of these cots might be kept in a store-room for emergency 46 These cots are so light that when folded a number can be carried on a hand-truck: they are specially useful in a camp esac te Sts ee “ME 1 d ship is the me hull gi into th board, loading just w the gr carry some I ship, h or not stowed For the m from t the sat marks bow a readin total « figure, appliet ship’s displac metho: can be the da the qu The and p accura of subi hull, v that p: by thi at the times consist cury ( or sca corres air-pu conne ance-c small The one-in deterr below and € coppel of the ment. either Office, consul The ; balanc q in T he Fage a

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hly aa shat for- rom the ylet- few ars. ckly the ned toa lay- that kly, and ap- the such rmal g in hese ught soon ch in while aring da ck; Reading a Ship’s Draft from the Bridge With this invention a shipmaster may know at a glance the draft, trim, and cargo weight of his ship “HAT a ship’s master should know ‘| at all times, both at sea and in dock, the draft and trim of his ship is imperative. In dock, if he has the means of reading the draft as the hull gradually sinks lower and lower into the water as the cargo is taken on board, he can tell the progress made in loading, the weight of the cargo, and just when the boat has taken aboard the greatest amount of cargo it can carry with safety. Again, if he has some means of knowing the trim of his ship, he will be able to judge whether or not the cargo is being properly stowed. For centuries the draft of ships and the manner of determining the trim from the draft has been recorded by the same crude method of reading the marks on the outside of the hull, at the bow and stern of the vessel. These readings are added together and the total divided by two. The resulting figure, called the mean draft, is then applied to a scale, furnished by the ship’s builder, to ascertain the tons displaced. It will be seen that this method may be far from accurate and can be applied only in still water. In the dark its use is altogether out of the question. The Instrument in Detail There has been devised a very simple and practical instrument that shows accurately and constantly the degree of submersion at any point of a vessel’s hull, which is, of course, the draft at that point. Usually the readings made by this instrument are taken at points at the bow and stern of a vessel; some- times amidships as well. The device consists of a balance-chamber, a mer- cury (or other) gage that is calibrated or scaled in feet and inches, and the corresponding weight and volume, an air-pump, and a control valve that is connected to the gage and to the bal- ance-chamber and air-pump through small piping. The balance-chambers, connected to one-inch sea-valves, are located at pre- determined points, forward and aft, below the light-draft line of the ship, and are connected by quarter-inch copper tubing to the mercury columns of the registering part of the instru- ment. This register or gage is located either on the bridge or in the captain’s office, where it may be conveniently consulted by the navigating officer. The water, in trying to enter the balance- chamber, compresses the air in the pipe leading to the mercury- fage and causes the mercury to rise or Tur PUMP To , © MAINTAIN PRESSU L IN TUBES With this instrument, which may be placed in the captain’s office or on the bridge, the navigator can tell at a glance the draft and trim of his ship fall in direct ratio to the vessel’s draft. In operating the instrument, the control valve is first shut and the line from the reservoir is opened to admit air into the balance-chamber. When this is done, the air reservoir is shut off and the control valve opens the pipe line between the balance-chamber and the gage. In the gage are two mercury columns, one showing the draft for- ward, the other the draft aft. How the Mean Draft Is Obtained When the forward draft is deter- mined, a knife edge traveling on a rod beside the forward mercury column is set exactly at the top of the mercury 47 column. The same thing is done with the aft mercury column, which has a like knife edge fitted in a rod beside it. When these two knife edges are in place, a central knife edge automatic- ally registers the mean draft and the corresponding tons displaced. The mean draft may be obtained direct by having a third sea connection amidship installed and assigning to it its own gage. As the displacement or dead weight of a vessel represents its weight and all it contains, the amount of weight put on board or taken off the vessel can be readily ascertained by taking the difference between the two successive readings of the dead-weight scale.

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Popular Science Moni/\ly Two Palm-Leaves Make 4 wh. a Rain-Coat S N the Philippine Islands rain-coats are not made—they grow by Nature’s grace. When the thinly clad native is caught in a storm, he goes to the nearest palm-tree, plucks two of the largest leaves, and hangs them from his shoulders—one in front and one in back. If he is at all particular about his hat, he will spread a third leaf over it. Rain-hats, however, are common in the Philippines. They are made of closely woven palm-leaves and are conical in shape. The Filipino shown in the picture aboye is wearing one. as well as his rain- coat. Relics of the Vikings N Victoria Land, north of our conti- nent, stand the remains of stone houses built undoubtedly by the naviga- tors, who, as far as we know, were the first to visit this continent from the Atlantic side. Humboldt affirms that the - Mongols first voyaged to the shores of the western coast several thousand years ago. The picture below was taken on Victoria Land, north of the Dolphin and Union straits, by W. V. Bruce, of the Canadian Arctic Expedition. The man _ standing with an alpenstock is Dr. Anderson of the expedition. You Can Wear This Bed See you sleep lying flat on your back all night? If so, you will be interested in a combination bed and overcoat recently invented by Mrs. Ray Werner, of San Francisco. With such a coat on your back you can sleep in comfort anywhere. It is recommended to‘soldiers and campers. A water-tight, airproof bag is rolled up and attached to the coat at the shoulders; another smaller bag is placed just above it. Neither bag weighs much, and thus they do not bother you. When night comes, you unstrap them and blow them up as you would a basketball—there are two valves quite near your mouth for the purpose. The lower bag spreads out and becomes a mattress, the upper one a pillow. If you carry a pack, you might slip it underneath the pillow. Crossing the English Channel in Nine Minutes LYING at the rate of 200 miles an hour, R. Vaughan Fowler, with two passen- gers, flew across the Channel, thirty miles, in just nine minutes. The trip was made in a D.H.4 equipped with a Rolls Royce Eagle engine of 375 horsepower. The whole distance from Cricklewood to Paris was maae in 1 hour and 45 minutes. Testing the Temper of an Eskimo Dog ITHOUT the dog the discovery of the North and South Poles would have been impossible. To the Eskimo and Indian of the far north the dog is a neces- sity. The Indian, less intelligent than the Eskimo, lets his dogs run wild in the sum- mer. The picture represents the way Captain Patten, of the Hudson’s Bay Company, tests the disposition of his dogs. If the dog submits to the test without showing a vicious nature, he is petted and allowed to run with less restriction than a dog showing a less kindly disposition. Kenai ena Berlin’s Floating Church HE sailor is supposed to be a peculiarly godless specimen of the human species. His swearing has become proverbial. He 3 hasn’t the opportunity to go to church, P which, according to some, accounts for his carefree attitude toward this life and | the life to come. -In most parts of the world they have established churches for sailors. The most pretentious of these is the seamen’s church of Berlin. Just why Berlin should have such a A It is not a seaport. § church is a mystery. But perhaps the swearing variety of Ger- man bargeman needs religious instruction. © Kadel & Herbert | &, in. whie desti emp! T) carri veyc whic chut grea com dail T ona pre fron

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ii! ly r of of the have » and neces- n the > Sum- aptain ipany, If the wing a wed to lowing h uliarly pecies. |. He hurch, its for fe and r have The amen’s uch a aport. f Ger- tion. lerbert 4 | A pril, 1921 Keystone View Company Burning Boxes Wholesale C=" oil is highly inflammable and - to prevent a serious fire the boxes in which it is shipped from the tropics must be destroyed immediately after they are emptied. They are loaded on a heavy truck and carried to the foot of the mechanical con- veyor shown in the picture above, by which they are carried to the top of the chute. They slide from this point into a great bonfire where hundreds of them come to the end of their long journey daily. They are burned on a sandy beach to prevent the fire from spreading. : Courtesy of F. Davidson & Co., London Seen through a Fly’s Eye A “FLY’S-EYE view” has been made possible by photographing the images formed by the lenses of a fly’s eye. Unlike our. own eyes, the eyes of various insects and-flies are composed of a num: ber-of lenses. The lens of the human eye forms but one image upon the retina; but the lens of a fly’s eye forms a’-number of images too small to be seen except by micro- scope: A powerful microscope was ar- ranged to focus these images upon the photographic plate. A statue was the object whose image was formed by the multi-lens eye, and here we can see a few of the images of the statue as seen in a “fly’s-eye”’ view. The Diagonal Sliding Drawbridge MERE are many kinds of drawbridges: some revalve, some swing upward, some swing sideways. And now there is one that swings sideways and backward at the same time, traveling in a straight diago- nal line. Since a straight line is the shortest distance between two points, per- haps this drawbridge will do its work in the shortest possible time. The bridge is mounted on wheels that travel on rails that are placed at an angle cf forty-five degrees to the river and the bridge. When a boat wishes to pass, the bridge-tender operates a winch that pulls the bridge sideways and backward on the tracks, until it is no longer over the river. Guided by the Light on a Cloud N the night, when low clouds float in a thin veil above the river, where search- lights on battleships throw their beam; upon them, a curious round patch of light can be seen on a cloud. Airmen flying above these clouds would also see the pateh of light and, in clear weather, the long beams cast upward into the sky. The suggestion has been offered that air- lighthouses should be provided with vertical searchlights of great power. Even in moderately foggy weather the light would penetrate the cloud of mist and be visible from above. What the Waves Did to These Rocks me ATER wears away a stone” is a literal truth that any one can see proved any day by observing the coast of a large body of water. Upon the shore of the Bay of Fundy, where the tides rise higher than anywhere else in the world, can be seen curious wave- worn rocks, such as are shown in the picture to the left. The fantastic forms at Hopewell cape have been produced by water that has washed away the less resisting portions. So little is left of the bases that the rocks are almost in an unstable condition. Of course, in time they will come down with a crash. But today they stand like pylons at the gates of the sea. Their size can be estimated by comparing them with the figure of the man standing beside one of them.

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Popular Science Monhly © Ewing Galloway Miners Drill Coal with Compressed Air Sucking Up Grain through a Big Pipe LWAYS there is a need for a compressor that will compress, HE manager of this grain-elevator has certainly got the right 4 wherever it may be. This machine is electrically driven and idea about unloading grain and moving it from one part of the carries its feed cable with it. grain-elevator to another. He uses the same principle as that Here it is shown at work in a coal-mine, supplying compressed employed by the vacuum cleaner. air to a coal drill. It is mounted on a truck so that it may roll on Large vacuum pumps are connected to the big pipe shown in the the same track used for the mine locomotive. center of the photograph. This carries grain away as fast as the A small air-tank built for high pressure is carried on the truck workmen can keep it piled up at its mouth. Many hundred tons and the supply is furnished from this. This compressed-air outfit is not only used in coal-mines, but for hammers, cement-guns, punches, etc. X-Raying Finger-Prints INGER-PRINT identification is based on the possibility of examining and com- paring tinder the magnifying-glass the prints of an inked finger. A specialist in the field of criminalistics, S. Nelken, of Berlin, has devised an im- portant improvement in this art. X-ray pictures of the finger with the muscles and bones are ob- tained. This is done without the use of any chemicals that can obstruct the delicate fur- rows of the finger-lines. More- over, the finger bone is shaped so characteristic- ally as to aid iden- tification. Whenever there j is a certain likeness of finger lines, the bones are examined to see if further research would be necessary. may be sucked away in a single day. The suction type of conveyor also tends She Is a Mother to Busy to eliminate dust and thereby helps to Little Submarines prevent explosions. ERE’S a queer-looking craft. She was not built for speed—that is ap- parent in her bulkiness, which is anything but the grace of speed-craft. British naval experts designed her to watch over sub- marines and to carry their supplies. The big steel “‘blisters’’ at each side are filled with water to ward off torpedo at- tacks. If a torpedo strikes these “‘blis- ters’ and tears them open, no harm is done, since they are filled with water. There- fore the buoyancy of the vessel is not af- fected in the least. The big vessel, lazy as she looks, is not strictly a fighter. Still, in the event of having to protect herself, she has a number of small ™® guns mounted above and below deck, | although they are not vieible. When They Got It in the Neck NSTITUTIONS for the deaf and dumb in the United States have a very hard time keeping their juvenile charges from getting lost when they are permitted to go on the street. Once they are lost, they are unable to make people understand where they wish to go, and consequently they have a great deal of trouble in getting back to their institution. Now some one has hit on the happy idea of writing the chil- dren’s name and address on the back of the neck. It is not tattooed on—that would : be too cruel and a would saver too ¢ much of branding An indelible pen- cil is used, the markings of whic! may be removed when they have served their pur pose. abo rah hav han and hol loc] wit the clos har pla T-c the anc put see pos pla reli of ear lint ind as

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ht he jal he he ns to —ea&rqr—————— wa 4j (— : | pril. 1921 Put a Collar on the Bag for Safety T= closing arrangement for bags shown in the picture above has proved to be of great ‘alue where numbers of bags have to be closed securely. It consists of an elastic metal band with teeth on both edges, and a T-clasp, provided with a hole for the insertion of a pad- lock. These bands are made in a variety of sizes to conform with the varying thicknesses of the necks of the bags when closed. The material is gathered by hand, a suitable metal band placed around the neck, the T-clasp slipped in the slot at the opposite end of the band and, if necessary, a padlock is put through the hole in the clasp. How the Earth Revolves Cc you shut your eyes and see the earth go around the sun? If you have seen the interesting model shown here, it is possible to form a good idea of how our planet is tilted at any time of the year with relation to the great solar orb in the center of the solar system. In imagination extend a line from the earth to the sun’s center. Wherever this line intersects the surface of the sun, a mere dot on the great solar sphere would indicate the position and size of the earth as projected there. iit) @ada | a nia) | ; eer ieee | aay aa ig : utes | Mae | ie iat FE, ORE aR 8] Py EEE 88 hr ' » EM, te 8 oh c Sm mf i ets e Gut et “oh a 2 Re = ae _ eee oS re ea Illuminate the Stocking to Darn It ERE is an idea that will make darning easier. A new darning-last of oval form has been invented by Edna C. Smith, of Clifton Forge, Virginia. It is made of translucent mate- rial and is arranged to screw into a socket over a small electric lamp. The electric lamp illumi- nates the inside of the last and enables the darner to see the threads of the woven fabric; it is then easy to do a smooth darn. This invention also enables one to discover minute defects in any material. An ordinary flashlamp serves as the illuminant, and the trans- lucent ‘‘darning-egg”’ is satis- Painting One Office Building to Look Like Its Neighbor NEW-YORKERS, who rate their city’s skyline as the most impressive in the world, were particularly pleased when the Bush Terminal Company erected a tower- ing Gothic structure just west of the shopping zone. The delicate lines of the walls and the tower drew forth expressions of praise. But when the Wurlitzer build- ing began to rear its walls beside the Bush building, these art lovers felt affronted. The painters employed on the Wurlitzer building transformed its blank wall into a thing of lights and shadows,making it appear to be of Gothic design. These painted lines blend with the design of the Bush building. factory for both light and dark materials. Freeze Fruit to Keep It TRAWBERRIES, grapes, cherries, rasp- berries, and other small fruits, as well as tomatoes and some other vegetables, can be kept a long time intact from the germs that bring about decomposition. Germs may be present in the air and in the fruits, but their activity is suspended by freezing. The Department of Agriculture has found that fruits frozen to a temperature as low as 10 degrees F. or higher, up to 32 degrees, and then stored in a temperature not above 16 degrees, will keep for several months. © Harris & Ewing

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Castles in California HILE Mrs. McClain, of Alhambra, California, was building castles in the air, her son started building them on the ground. He built two of them— Diamond Castle and Tiree Castle, both duplicates of large castles in Scotland near which Mrs. McClain lived for many years. The duplicates are very much smaller than the originals, but they are alike in every respect. The rooms measure about eight by ten feet and are six feet high; the stairs are barely wide enough for a fat per- son to climb. Mrs. McClain and her clever son live in the smaller castle, the Tiree, and can see the larger castle, the Diamond, from their windows. The Diamond is shown herewith. Not many people can have the scenes of their youth actually recreated for them as Mrs. McClain has had. Oxesa & Herbert Practising Golf Strokes on Board Ship OW hard can you strike the ball? That is one of the secrets of good golf-playing. It is the kind of stroke and the strength of stroke that counts. When any one wants to succeed in any pursuit, keeping in practice is essential. This is true of golf as well as anything else, so a champion golf-player has devised this clever machine to keep in practice even while crossing the ocean on a steamship. The device is so arranged that the quality of stroke is registered on an indica- tor. The ball itself is fixed so that it can not be driven into the sea. Otherwise there would be a lively time chasing golf- balls on the water with life-boats. Not only is the golf machine suitable f-r the deck of a ship, it is also of service to the “champion player” who wants to prac- tice indoors, providing he has moderate space at his disposal. Popular Science Monthly Train a Tree in the Way It Should Grow MAN is shown above, fastening a vine to a wall. You may wonder what is unusual about that. The man is training a fruit-tree to climb the wall of his garden in France, thus achieving utility as well as beauty. By this method Europe has long ignored Nature’s ideas on how a tree should grow and when it should blossom. Planted against a wall with a southern exposure, a tree has no-option but to grow in one direction. As each branch sprouts, it is gently trained by cloth strips in the way it should grow. The sun-warmed wall encourages the tree’s growth, and months before the usual bearing-time, the wall-tree has ripened fruit to offer its owner. With patience, it is possible to train al- most every kind of fruit-tree to grow in this manner. A Machine that Travels from Job to Job Crushing Stone » ROTARY eee SCREEN » r\ Av ” ee Y bs BUCKET CONVEYOR HIS machine is always on the job when there are -any stones to be crushed. There has always been a great need for a portable stone-crusher small enough to meet the needs of the average con- tractor. A stone-crusher, however, is of STONE necessity such a heavy machine that until recently a successful light machine had not been manufactured. The stones are dumped into the crushing hopper from wheelbarrows. After being crushed, they drop into a bucket conveyor, from which they are dumped into a wagon. The stone-crusher is driven by a portable steam engine, electric motor, or gas engine. It is set up on wooden blocks when it is in use to prevent it from moving. The machine can be conveyed from job to job by the steam-roller or the motor- truck. ‘ 4s ie r the wis] on t the upo a mal rais mer pas: dan toes S the by but ste fusi The van say

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RRR Es ee x) ns % April, 1921 ‘‘QOpera Seats’’ in Street Cars N the street-car where the seats are ar- ranged in rows with an aisle between the passenger next to the window. who wishes to get out must cause the passenger on the aisle end of the seat to step out into the aisle or possibly have his toes trodden upon. This inconvenience is alleviated by making the seats so that they can be raised, thus requiring the end passenger merely to stand to permit the other to pass. There is plenty of room and no danger of stepping on the other fellow’s toes. Such an arrangement saves the time of the railroad company. The delay caused by the passenger who wants to get out, but has to wait for the end passenger to step into the aisle, and the resulting con- fusion, is detrimental to good service. The new-style car seat is thus an ad- vantage in the correction of this fault, to say nothing of tempers saved. What Happens to Wooden Propellers in a Storm HEN an airplane tries to make head- way through a storm, the speed of the machine adds to the speed of the flying missiles and raindrops become bullets. Lieutenant Charles B. Austin, flying from the Panama Canal Zone to Washington, was turned back by his encounter with such a storm. The effect of his battle with the elements is shown by the propeller. There is a new kind of propeller made of bakelite which would have withstood the storm. In one test of this material, the airplane nosed over in a muddy field, the propeller churning up the mud to a depth of twelve inches. Where Steady Nerves Count A UDIENCES in vaudeville theaters are familiar with the expert 4 juggler’s entertainment. He keeps a number of balls in the air, deftly catching them in his hands and alternately catching some of them in little pockets on his shoulders and on his back. One of his most clever tricks demonstrates just how steady one’s “nerve” can be trained. On his back he juggles three balls, send- ing first one, then the others, into their respective pockets. He does this by making one ball strike another. Any one who plays billiards knows that the art of sending the ball in the desired di- rection is a clever calculation of an- gles, followed by an accurate stroke with a cue. How does this man accomplish his results? Simplifying the Movie Spotlight ORRECT lighting is.-even more im- portant in making a movie film than it is on the stage. When the spotlights are mounted high, only the lamphouses are elevated, as on the top of a wall; it would hardly be practicable to raise the stands. But this spelled trouble. The electrician on high had to pull out the plugs to ex- tinguish the light at the command of the director; the switch was on the ground below. The result was arcing, and arcing in turn pitted the connectors. Pitting meant a flickering light. Claud Harding, chief electrician of the Lasky studio in Hollywood, California, and Frederick S. Mills, manager of the electric department, solved the problem simply by removing the switch and switch-box from the stem of the spotlight and mounting them on the back of the lighthead. They are always within reach. It will no longer be necessary to renew the connecting plugs several times a year at much expense. Music in Two Tin Cans geal two tin cans, attach them to the opposite ends of a piece of wood, and run a D or A violin string from one can to the other. The cans will furnish the resonance that is usually supplied by the body of the violin. Of course the range won’t be as great as when four strings are used, but if you use either of the medium-toned strings, you will be able to play practi- cally any tune. In the southern part of the United States it is a com- mon thing for peo- ple to make rude musical instru- ments. At har- vest-home festi- vals, notably in Atlanta, Georgia, one or more days are set apart for contests at which people, mostly from remote mountain regions, play these home- made contrivances for prizes, in groups or singly.

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Popular Science Monthly In a Bottomless Pit of Ice “Are you all right?’’ came a voice from above. ‘Yes, but I can not get up; I’m hung here,” was the answer. ‘‘Hang on, then!’’ shouted the man above. The man in the crevasse dangled helplessly over the bottomless icy pit, while his arms and legs gradually froze. This was the experience of John Lachlan Cope, sur- geon and biologist of the latest Shackleton antarctic expedition. To intensify the situation, the crevasse gradually widened. But the sledge harness from which he dangled saved him; for it held firm. Dr. Cope’s friends on the glacier above made a rope ladder, and on this, painfully and with infinite precaution, the surgeon slowly climbed back to comparative safety ‘

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April, 1921 ANGLING helplessly for hours over a bottomless pit of ice while arms and legs gradually froze—that was the experience of John Lachlan Cope, surgeon and biologist to the Ross Sea party of the Shackleton antaretie expedition. Mr. Cope (in Great Britain surgeons are called Mr.) had been leading three men over a dangerous glacier, and had failed to notice a crevasse that vas almost covered with snow. Sud- denly he felt the snow give way, and he fell headlong through space. The sledge harness, however, saved him. It was fastened around his chest and shoulders, and it held him suspended twenty feet below the edge of the crevasse, Fortunately, his companions saw him fall, and they immediately made fast the sledge ropes. Seen from a Rope’s End Cope looked around him. The cre- vasse in which he hung widened as it extended down into the earth. Huge columns of ice jutted out here and there. Some were blue in color, others a whitish pink. Many of them were weird and grotesque in shape. The crevasse continued to widen until its sides disappeared from view, and In a Bottomless Pit of Ice How an explorer fell into a crevasse and By Philip Schwarzbach below that—darkness and illimitable depths! “Are you all right?’’ came a voice. “Yes, but I can not get up; I’m hung here.” “Hang on, then!’’ shouted the man above. ‘‘We’ll make a rope ladder.”’ With that he disappeared. It grew colder and colder in the icy crevasse. Cope’s mitts fell off, and he watched them drop, striking the ice, until they disappeared from sight. His hands were soon numb and his body half frozen. Now and then the roar of ice falling down some far dis- tant crevasse broke the silence. At last the ladder was finished, and the men lowered it. All sense of touch being by this time gone, Mr. Cope had to watch his hands to see that they clutched the rope as he climbed. Swinging backward.and forward over the pit, he gradually made his way toward the top. But just before he reached it his harness came off. If he slipped, nothing would save him from being dashed to pieces. He was so numb and exhausted that his legs would not stretch far enough to reach from one rung of the ladder to the next. He called up faintly to the men and how he was saved they lowered the harness until he was able to push his legs through it. Half sitting in it and feebly grasping the rope ladder, he was hauled the few remaining feet to the surface. He had been hanging over that bottomless pit for three and a half hours! The Antarctic Once More! This intrepid explorer was later marooned for two years on Ross Island. Yet when he returned to civilization he immediately began to plan another trip to the antarctic. In this trip he intends to circumnavigate the entire antarctic region. It will take him at least five years. Captain Scott’s old ship, the Terra Nova, has been put into commission for the job. An airplane will be carried on board ship and, if conditions are favorable, an attempt to fly to the pole will be made. The ship will go back to New Zea- land, stock up for a four years’ cruise, and then return to the Ross Sea, . where the six men, left the year before, will be picked up. Then she will take up her task of circumnavigation. Mr. Cope hopes to keep in touch with civilization by means of wireless all during his trip. Extinguishing a Fire with Soda Water BIG fire was raging in the filling under a railroad trestle. The railroad company had placed in the “fll’? some ashes that contained some unburned coal. This was covered with blast-furnace slag. Spontaneous com- bustion occurred, and in a few days’ time the bottom of the fill was a roar- of carbonate of soda. Sixteen thousand pounds of soda was brought to the scene. This was dissolved in water and pumped to the fire through a two- _and-one-half-inch hose. When this solution came in contact with the hottest parts of the fire, violent ex- plosions occurred, throwing great vol- umes of slag and ashes high into the air. However, the explosions were not severe enough to spread the contents of the fill over a great area. Aftera few hours’ work the fire was com- pletely subdued. It is claimed that a solution of car- bonate of soda has a far greater cool- ing furnace which ing effect than forced the railroad F or oF Res ae water. The car- company to aban- . bon-dioxide gen- don its service. erated with this | oe One solution, coming Thomas, a fire en- , | in contact with a gineer, was called — -* | highly heated ma- to the scene. He . Pa terial, also tends was confronted to smother the with the problem fire. One gallon of saving the fill, of a solution of since the railroad carbonate of soda company did not has a fire-extin- want to go to the guishing effect expense of filling equivalent to one in the valley with hundred _ gallons fresh material. of water. This made _ the Carbon _ tetra- use of high explo-' chloride is a very sives impossible. efficient _fire-ex- Mr. Thomas im- tinguisher, but it mediately decided Pouring tons and tons of a solution of carbonate of soda into the hot fire. Violent is more expensive to use a solution explosions occurred that flung the earth and ashes many feet into the air 55 than the soda.

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The farmer may. generate enough cur- rent to supply his house and barn if fortunate enough to have a stream passing through his property Harnessing the Power of Small Streams HEREVER water runs to a lower level, there is power. This power is not commercialized because the total power obtained from each stream would not warrant the neces- sary investment in a dam and power plant. This can be done only in the case of high falls or a stretch of rapids where the water takes a large drop in a short distance. This power unit will generate cur- rent for domestic use if placed in the temperatures? industries. NY oMULTIPEY! - € Two water-wheels of the undershot variety are used; they will drive a 500-watt generator middle of a small stream with a cur- rent flow of two or more miles an hour. Two water-wheels of the under- shot type are used. These drive a small 500-watt generator, which is capable of supplying about twenty 25-watt lamps with current. Sixty Miles an Hour in a Wind-Car i ie E thrills of an airplane, the safety of an automobile, and the economy of a motorcycle, all are combined in the propeller-driven car designed by Sheldon F. Reese, of Huron, South Dakota. Ina six-hour endurance test this car ran sixty miles on forty-eight cents’ worth of gasoline. But two control levers are required. One spark lever controls the engine, while a foot lever controls the brake. The motor can be started from the seat. The work of repairing is greatly simplified and can be done without the aid of me- chanics. The distribution of weight is so devised that the car is easily managed by hand; it weighs only 160 pounds. The air-propelled: propeller is guarded by a broad metal hoop around the tips of the blades. The motor is fitted with mufflers which suppress much noise. In winter this little machine is as useful as in the summer. It can be run to the river or the lake and there quickly con- verted into a complete iceboat merely by substituting ice-run- ners for wheels. The motor is air-cooled, so that there is no danger of water in the radiator freezing. Equipped as an iceboat, the machine weighs slightly more than 150 pounds and its speed varies from four to sixty miles an hour on the ice. The car carries two persons. A twin-cylinder engine of six horse- power is mounted on the rear axle. The propeller is made of walnut and is eight by twenty-eight inches. Here is an automobile driven by a pro- peller. It makes sixty miles an hour at less than one cent a mile 56 Popular Science Monihly Hazards of Heat in Industry N industry there are the so-called “hot jobs.” the industrial health hazards of working under high What are The United States Public Health Service is undertaking a countrywide investigation. workers need not be exposed to high temperature in some Perhaps methods can be devised of protecting workers where they must of necessity be exposed. Long exposures to heat lower the general health and may cause joint and muscular rheumatism, skin disease, and hardening of the arteries. Perhaps it may turn out that Both employer and employee suffer, the one in business and the other in earning power and health. It is likely that the investigation of the United States Public Health Ser- vice will show that hot-water and steam pipes, boilers and fire-rooms, have been improperly placed, or that steam-operated machinery has been placed unnecessarily near boilers. Heat can be greatly diminished by water-jacketing boilers, by insulating glass surfaces with double walls of fire-brick, and by kindred devices. Big electric fans will keep the air moving and make hot rooms more comfortable. Burning, radiant heat can be screened by wire or loosely hanging chains through which the workmen can pass. COMBUSTION = CHAMBER The oil circulates through the outer casing of the furnace before it passes into the burner Warm the Gas Before It Burns IL vapor and air are mixed and heated before entering the com- bustion chamber of this furnace. The air supply first circulates through a casing arranged about the com- bustion chamber. This compart- ment is kept very hot and the air passing through is raised to a high temperature. The air leaves the compartment and mixes with the oil vapor just before it enters the combustion chamber. The pre-heating of the air pre- vents cold air from reaching the refractory lining of the furnace. Thus the heating of the air also results in longer furnace life. A small blower keeps air circulating through the outer casing of the furnace. The oil is also fed to the burners under pressure. [ ‘SI b ber of ence @ serious design a fre tro! co serves As t ism 0! pass i invent not lie the p be in froma (prefe: three behing seat i Morec is no | using magne cordir able a on bo the ac The up ir alecoh bowl consis desce cast 1 comp strike resist lighte pass, No

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a oe = Ge wo se © yes ers re- US in ver ter lso April, 1921 Steering [ ‘SING ordinary compasses on board airplanes involves a num- ber of difficulties, of which the influ- ence exerted by iron parts is the most serious. This is why the instrument designed by Carl Bamberg, called a ‘remote con- an Airplane Automatically By Dr. Alfred Gradenwitz diaphragm, which, in a given position, covers both beams of light, thus leaving both selenium cells in the dark. As the compass bow] is turned around its vertical axis (the magnet system re- maining in its previous position, trol compass,”’ de- Jian serves attention. , As the mechan- ism of the com- pass in the new invention need not lie in view of the pilot, it can be installed far from all iron parts (preferably from three to five feet behind the rear seat in the hull). Moreover, there is no objection to using as strongly xX magnetic and ac- cordingly as reli- able a compass as on board sea vessels, thus increasing the accuracy of readings. The magnet system is, as usual, hung up in a compass bowl filled with alcohol-water. At the bottom of the bowl are two lighting systems, each consisting of a small electric incan- descent lamp and a set of lenses to cast two beams of light through the compass liquid. These two beams strike two selenium cells, the electrical resistance of which drops as they are lighted, allowing an electric current to pass, and causing the hand to deflect. Now, each magnet system carries a Arranging the new compass that makes use of cells, lenses, an incandescent lamp, and a magnet INDICATOR OU! NS =“ = ee =r \ i . 1” vi) \ ~ J — —_— of the compass NN bowl, that is, an \ increasing or de- creasing electrical 2. resistance of the | selenium cells, is ee : vty | obtained. Any | airplane or sea- plane fitted with this arrangement can accordingly be steered accurately in a given direc- tion, any deflec- tion being equiv- alent to a rotation of the compass bowl with regard Joa i ed pointing north-south), one or the other of the selenium cells will emerge from the shadow of the diaphragm into one of the two beams of light, thus causing the electrical indicator to deflect to the right or left. Whenever the compass bowl is turned, the amount of the turn can be read from the indicator, the deflection of the hand being the greater as the deflection from the course is greater. In fact, by beveling the edge of the diaphragm, a gradual increase or de- crease of the intensity of illumination corresponding to a _ given rotation selenium to the magnet system. In fact, the pilot has but to operate the vertical rudder to the right or left, according as the course indicator is deflected to left or right. If now the compass bow! be turned through a certain angle, say thirty five degrees, relatively to the longitudi- nal axis of the airplane, the pilot has only to fly according to the course- indicator in order to cause the new course to deviate thirty-five degrees from the initial direction, one of the selenium cells being lighted until it is brought back into the shadow of the dial diaphragm by turning the air- plane round through the same angle. a ae ae a a ah With the aid of radiotel- ephony, a fire chief may now sit in his office and give directions to the vari- ous units of his department. Every station will have a radiophone, and—as shown in the picture above—one truck of each company will have portable equipment A single wire is used for the antenne. In the center ‘picture a fireman is attach- ing this toa lamp-post. It may also be attached to a telegraph-pole or a tree. The right-hand picture above shows a crew of radio firemen getting ready for their work

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Above: An inspector de- termining the depth of penetration with a small auger. At right: This shows how the new prep- aration penetrates the wood to a depth of one inch. Many years are added to the life of a pole throughthis process This Preservative Keeps Telegraph-Poles Fit HE butt of a telegraph-pole decays rapidly unless it has been treated with a preservative. The pole butt rots away, and with the first severe wind-storm down comes the pole. Not only does this cause interruptions in service, but it also costs the telegraph, telephone, and electric companies large sums of money, not to mention the accidents to human beings and animals. Chemists searched long for a really good wood preservative. A good pre- servative was found, but there re- mained the problem of making it penetrate the butt of the pole under treatment. A mere “skin’’ penetration is not sufficient. A number of different processes have been used, with no startling success. A solution is found for every prob- lem. A new process has been per- fected that places absolute control over the penetration of preservatives into telegraph-pole butts. Heretofore, much of the trouble has been caused by unequal penetration. Treated poles often came out of the process with complete penetration on one side and partial penetration on the opposite side. The new method brings about complete and uniform penetra- tion for a distance of from one half to one inch. A pure coal-tar distillate is used that prevents the injurious bacteria and fungi getting into the wood. The preservative is forced into the pores of the wood under pressure. This development. may appear some- what trivial to the man in the street until he learns that this method of pole preservation will save more than twelve thousand acres of forest a year. it will do much toward the conserva-’ tion of our national woodlands. ECHANICAL han- dling has progressed to the point where special handling machinery is be- ing developed for the con- veyance of every class of material. Here is a small but powerful electric truck for the handling of paper rolls. A scooplike arrange- ment is placed on the front of the truck. This slides on the floor. The scoop wedges itself under the paper roll, the operator closes The scoop drops down, passes under the paper, and lifts it up Popular Science Monthly Moving Rolls with Electric Trucks This truck was made especially to handle large, heavy rolls of paper a motor circuit, and the paper is lifted clear off the floor and held ready for transportation. The gears are shifted, and away goes the heavy roll to an- other part of the paper-mill or printing- plant. A half-ton roll of paper may he lifted and carried to any part of a plant without being touched with the human hand. The lifting scoop is arranged on a swivel so that the roll may be turned and set down on its end, should that way be more convenient. Plywood—Stronger than Natural Wood OOD has always been an inter- esting object of study. With the advent of the airplane the study has become much more intense. The pictures show experts of the Forest Products Laboratory, Madison, Wisconsin, making a study of veneer and plywood. Strips of veneer—sheets of wood cut from the end or face of a revolving log —are fastened together, forming the Screw fastenings of the plywood are used, among the various methods of testing. The force required to tear through the wood is mneasured, and the strength of different kinds of wood is tried 58 plywood, used in the manufacture of en- gine bases and other parts of airplanes. A broad, thin sheet of veneer would soon split if required to support any great weight. Fasten two or more sheets of veneer together, however, with the grain of the wood running in different directions, and the danger of splitting is largely overcome. The veneer can also be fastened together so as to help overcome warping of the wood from moisture, something to avoid in airplanes. Tests were made with thirty-five dif- ferent woods to de- velop the best ply- wood for airplanes. A report prepared by the National Ad- visory Committee on Aeronautics, at Washington, D.'C., ought to be read by every manufacturer, for plywood can be used to make trunks and other receptacles. The strength of the plywood is tested by the splitting method. The veneered block is attached to the end of a sharp pointer and a gage measures the force required to split the block 2. ag ~ ye 3 p tin dust rie machi! other anothe It is ranged A pow big bel on it destin: belt in loaded pulley B rangec accom Ton shiftec a VOT) conve: to mo — shaken. oa pais aA whee moto track electr Th again railre bile high react be t faste back abou cars and, twice Su with, and » and | have

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nthi y to er ifted y for fted, ) an- ting- y he slant iman on a irned that of en- anes. yould ; any more ever, ning unger The ether f the ture, void nade dif- » de- ply- anes. vared | Ad- Pe On 3, at d by urer, unks icles. f the ed by thod. block 1e end sinter sures ed to April, 1921 Cut the Hauling Cost by Portable Machinery ‘ETTING material from one y place to another in a short time that is the secret of in- dustrial efficiency today. Here isa machine that will get coal, stone, or other materials from one place to another on short order. I: is a portable belt-conveyor ar- ranved to travel on a railroad track. A powerful electric motor keeps the big beltin motion. Material placed on it is conveyed rapidly to its destination, where it falls off the belt into a chute. When the belt is loaded down, it comes to rest on the pulleys underneath. These are ar- ranged in a semicircle, the better to accommodate the belt. Tons and tons of material may be shifted from one place to another in a very short time with this new conveyor. The motor is also used to move the machine about. A portable belt-conveyor that will get material from one place to another in record time Turning Motor-Cars into Railroad Trains AKE the rubber tires off an auto- mobile, put in their place iron car- wheels, and you will have a railway motor-ear that will follow the car- tracks just as well as a steam or electric locomotive. The chief objection raised against the use of automobiles for railroad work is that an automo- bile can’t travel backward at a high rate of speed. Thus when it reaches the end of the line it has to be turned around. But if you fasten two automobiles back to back, you don’t need to worry about turning them around. The cars take turns acting as trailers and, incidentally, accommodate twice as many people. Such a dual train is shown here- with. It will carry fifty passengers and will cover about one hundred and fifty miles a day. Both cars have two pairs of front wheels. An enterprising newspaper edi- tor beat the telegraph by send ing out a wireless*equipped air- plane, properly manned, to hover over a race-track and re- port. the results of the race Radio and Airplane Win Newspaper Scoop NEW factor has entered into newspaper reportorial work that may revolutionize the whole business. Heretofore horse races, automo- bile races, and other events have had to be reported to the news- papers by telegraph. Now an en- terprising London newspaper has gone the disciples of Morse one better. Recently a horse race took place at Ascot in which all England was interested. So the editor of this news- paper decided to have the race reported from ,an airplane, not only, because it would he a distinct novelty to:publish the story as being aerially reported, but also because he thought he could: in this way actually beat the telegraph. He engaged a plane with a pilot and a wireless operator and sent them out to hover over the race-course and report what they saw by wireless direct to the newspaper office. No doubt he got the idea from the work of the re- connaissance planes during the war, which directed the fire of the gunners far back of the lines by wireless. The aviators were a distinct success. They were able to follow the racers around the track, reporting in detail the position of each at various dis- tances, and sending a vivid story such as no observer stationed in the grand- stand could give them. The plan was eminently successful. ‘ ih ta i sail ety x oe a St ee Sa OE Two automobiles with iron wheels, fastened together back to back make an ex- cellent railroad train. The two cars act alternately as trailers 99

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Hammering Water to Drive The startling HROW a pebble into a pool of water. Waves ripple out in every direction. These waves are power waves; for the pebble suddenly displaced the water— pushed it away. This has been known for centuries. But it has remained for a brilliant invent- or, Mr. George Con- stantinesco, to apply waves to the actual driving of ma- chinery. His invention must be regarded as one of the most startling made in our time. The waves in pools dissi- pate their power. They spread out rapidly in all directions. But suppose they could be set up in a pipe full of water. And _ suppose, further, that they were set up anew constantly by some device. That, in brief, is the essence of Mr. Constantin- esco’s invention. Mr. Constantinesco’s ideas have been carried out practically in various mechanical forms by Mr. Walter Haddon and Messrs. W. H. Dorman © Modern Publishing Company here shown; other end. He is carrying the piping used for a rock-drill In order that several machines may be driven as they new invention of and Company, of Staf- ford, England, for which reason English engineers are beginning to speak of the ‘“‘Dorman sys- tem.”’ The accompany- ing illustrations show these practical applica- tions so clearly that the reader has only to refer to them to learn how waves of water in pipes can drive such machines as rock-drills, riveters, and motors in general. Water, as everybody knows, is practically in- compressible. But not every one knows that it is also slightly elastic. Because it is elastic Mr. Constantinesco’s ideas are practical. Suppose a water-filled pipe is sealed at one end. At the other end is an engine, a ‘‘generator’ of waves. The generator has a piston, which strikes the water so many blows a minute. The usual slow-moving piston would compress the water elastically through the entire length of the pipe, so that it would all be under uniform pressure. This hammer-piston does not act in Popular Science Monthl, Machinery Constantinesco this way. Each blow sets up a suddei impulse. Near the piston the water suddenly compressed. A little time elapses before the wave of compressio is received by the water in the far en‘! of the pipe. Hence there is a high- pressure zone near the hammer-piston; then a low-pressure zone; next a higl- pressure zone. So high- and low- pressure zones alternate, until final! the blow is received at the end of the pipe. These high-pressure zones cor- respond with the crests of the waves formed when a pebble is thrown into a pool of water; the low-pressure zones with the valleys. At the end of a sealed pipe the wave is, of course, reflected back again. It is evident that the power im- pulse that is reflected back in a sealed pipe must not interfere with another forward impulse set up by a blow of the piston. Start a pendulum swing- ing, and you can keep it beating with the slightest tap of the finger—if the tap is timed correctly. Unless the tap is applied at just the right instant, the pendulum may be stopped. The wave impulses in the sealed pipe act like a pendulum. The blow struck by the piston must fall on the water at the right instant. Hence, if the blows of the piston are timed correctly, the in the article Owele 4 WATER PIPE LINE ¢ ; Of 15000 tbe pes E Ball and Socke? ints: the Balls ced b +s! eee oy? suitable lengths 3 ‘ Se % . = ry Drawing by S. W. Clatworthy How Power Is Transmitted through Pipes Filled with Water At one end of a pipe filled with water is a wave generator at the other end a piece of machinery to be driven. The wave generator is simply a device to hammer the water in the pipe periodically. The hammering sets up power waves in the water, and these waves drive the machine at the . are needed, and therefore not necessarily simultaneously, “capacities” are introduced. The purpose of these is described The. pipe that connects the capacities has an air-release valve, and so has every tool or motor driven. If trapped air were not released, it would create surges and affect the water pressure. April, 1 my STAT) high- ; reflecteé those t other \ the pis to be s » the far ; the poy plied u But it is « motor Still, essenti ton) a must will be It r

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W - h , Or- ves ito im- led her of ng- rith the tap the yipe uck r at OWS the rthy

April, 1921

en

| 3) WAVES s ATIONARY |F

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. © Modern Publishing Company

a half. The wave generator containing the piston is driven either electrically or mechanically. The waves travel at the rate of

g compressed atin ~ nd of uot pressure — eS @) WAVES MOVING TOAND FRO fu Receiver or Working Piston a Bees at 7,

= «ae Pistor lou *

How Tools Are Driven by Water Waves Set Up in Pipes The principle by which water is: hammered in order: to set up power waves’to drive machinery is here shown. hammer takes the form of a piston that has a stroke of less than an inch and a diameter of slightly more than an inch and The and twenty feet. fifty pounds. being hammered exact \— “ArautTipie Sof wave length TUBE COMPLETELY FILLED WITH WATER yy. GENERATOR PISTON forty-eight hundred feet a second. forty revolutions a second gives a wave-length of one hundred The maximum pressure is usually fifteen hundred pounds to the square inch, and the average seven hundred and Water in the pipe cannot freeze while it is | y mee TRAVELLING ALONG

A. HIGH PRESSURE ZONES B. LOW DITTO

Drawing by S. W. Clatworthy A generator speed of

high- and low-pressure waves of the reflected impulses will coincide with | those of the forward impulses. In other words, a reflected wave reaches the piston again just as a new blow is to be struck. If the pipe is sealed at the far end, as we have been assuming, the power of the waves would be multi- plied until finally the pipe would burst. But the pipe is not sealed. Instead, it is connected with some form of motor that is driven by the impulses. Still, correct timing of the blows is essential. The wave generator (pis- ton) and the motor at the other end must run in harmony, so the blows will be delivered at the right time. It may be difficult to understand why a sudden blow of a hammer piston on water should act differently from the slow push of an ordinary piston. Suppose that you have a row of bowling-alley balls in a runway, each ball in contact with the next. Then suppose that you were to strike the first ball a blow. The shock would be transmitted to the last ball. Only that ball would move; the intermedi- ate balls would remain practically stationary. A power wave has been transmitted from the struck ball to the last. The Dorman wave-power system works on this principle. It is more convenient and more efficient to use a liquid like water, which com- 61 pletely fills a pipe, than a series of balls or some solid substance. Wave power is also transmitted by a’ carpet when you shake it in the right way. Pick it up by one corner and give it a quick up-and-down move- ment. A wave travels to the outer- most edge of the carpet; yet the carpet as a whole is not shifted from its posi- tion. So it is with the water in the pipe of the Dorman system. A pipe line can be branched so as to serve a number of machines. Each machine is so placed that it receives impulses at the right time. The engineer in his technical parlance says that it is stationed at an exact number of wave or half-wave lengths in the

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line. A motor inserted at the wrong place (a quarter or three quarter wave length) would not work. Running Several Machines Suppose that all these machines are not working at once. Does this render the whole system worthless? Not at all. What is called a “capacity”’ is introduced into the main pipe. .The “capacity” is merely a chamber. At each blow of the piston the water in the capacity chamber is compressed, only to expand again between blows. It acts, therefore, as a kind of spring to absorb the surplus energy and give it back between blows. Thus the wave generator is called upon to per- form work equal to the energy utilized by thé machines actually in opera- tion. A typical ten-horsepower generator rotates at a speed of twenty-four HEN you look at the bony bat and arm below, you think they are X-ray pictures, taken by an X-ray machine. But that is not so. The arm, for instance, is a real flesh- covered arm immersed in a liquid that has certain refractive properties that make the flesh invisible. The picture was taken with an ordinary camera. This peculiar liquid that renders things invisible, or rather transparent, was invented by Dr. J. H. Stean, of Worcester, Massachusetts. What happens? The liquid has the same in- hundred revolutions a minute, which means that forty wave impulses are set up each second. That the piston is really a kind of hammer is shown by the fact that it has a stroke of only 29/32 of an inch, and a diameter of slightly more than 1 9/16 inches. Although in field plants it is simple enough to take a branch at a point that will bring a rock-drill to within a multiple of an exact wave or half-wave length from the generator, in factories and buildings, where space is of impor- tance, surplus lengths of piping might be inconvenient. A simple device known as a condenser is therefore used. It consists of a short cylinder of a larger diameter than the pipe, which is inserted in the main at any point de- sired. In this cylinder is a free piston, upon one side of which the waves strike and which in turn passes on the impulse to the water on the other side of it. Normally the piston is main- How to Become Transparent A peculiar liquid that renders flesh invisible dex of refraction as the flesh. By this we mean that the light rays passing through the liquid are not bent, or re- fracted, when they pass through the flesh of the arm. Thus the flesh be- comes invisible. To further illustrate this, take for example a glass tube. When you hold it in the air it is plainly seen, since the light rays passing through the ‘at- mosphere are bent on entering it. If you place that glass tube in water Popular Science Monthly tained centrally in the cylinder by a spring on each side. From this cylin- der a branch is led to a machine, aid as the cylinder serves as a “capacity,” it may be inserted in the pipe main when necessary. Water the Sole Requisite The importance of this apparent y small detail cannot be exaggerate.|. It makes it possible to place a motir anywhere—even in close proximity ‘0 the generator—so that wave-pow transmission is not limited to long d tances. Not the least astonishing feature that water can be drawn off at one e1 of a pipe main and replenished at the generator end while the plant is «at work, without affecting the efficiency of the wave transmission. Thus water for rock-drills is taken from the pipe mains. “= tf it will not be near- ly so distinct as when in the air. The index of re- fraction of water is almost the same as that of glass; thus the rays are bent very slightly when they pass from the water to the glass. Different parts of an animal’s body have different indices of refraction, but it is possible to make any part disappear by submerging the animal in the proper liquid. A good mixture for making flesh invisible is three parts of salicylic methyl ester and one part of benzyl benzoate. — ~ ——— oe © Keystone View Company This is not a skeleton, but a picture of a real, flesh-covered bat that has been immersed in a liquid that makes its flesh invisible 62 } © Keystone View Company This arm was in a liquid with the same index of refraction as flesh : OW H spi surface ¢ parachut ope! in at that a world at this ren Second I] the Unit of the known | mite’” W Lieute permissi leap fro At 4 Pa June, af in insp “chute,’ D. H. 4. by Lieu They cli an hou registere thousan It wa but at t ing col B stood o shiverin the pilo a little, backwa of the s Like Acco! droppec rare at pulling parachu time, al Telease paracht opened break 1 folds of up with threads doubtfu terial strain after so tum ha In th utes af chute tenant feel no tionine He seei pended air, F Sudden caught

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ear- 5 as air. Tre- e as bent the ody tion, part imal ture arts part Aprii. 1921 “Dynamite Wilson” Jumps from the Clouds Four miles he dropped, held up only by a little silk parachute H OW does it feel to step out into space about four miles above the surface of the earth with a small silk parachute that is not guaranteed to oper in the thin atmosphere existing at that altitude? Only one man in the world at the present writing has had this remarkable experience. He is Second Lieutenant John H. Wilson, of the United States Air Service, member of the 96th Aero Squadron, better known by his army name of ‘‘Dyna- mite’ Wilson. Lieutenant Wilson obtained permission to make a parachute leap from twenty thousand feet. At 4 P.M. on the seventh of last June, after spending half the day in inspecting and folding his “chute,” he started up in a D. H. 4B bombing-plane piloted by Lieutenant Delmar Dunton. They climbed in circles for about an hour until the instruments registered higher than twenty thousand feet. It was a hot Texas day below, but at that altitude it was freez- ing cold. Lieutenant Wilson stood on the edge of his seat shivering with cold, and when the pilot slowed down the motor alittle, he made a powerful leap backward and cleared the wires of the ship. Like a Rock He Dropped According to his statement, he dropped like a rock through the cold, rare atmosphere, at the same time pulling the release mechanism of the parachute. After an unusually long time, and as he was about to pull the release of his second or emergency parachute, which was carried to be opened near the ground to further break the fall, the wind caught the folds of silk and brought the lieutenant up with a heavy jerk. The threads held! It had been doubtful whether the ma- terial would stand the strain of the check after so much momen- tum had been gained. In the first few min- Oe utes after the para- _ chute opened, Lieu- tenant Wilson could feel no apparent mo- tion in either direction. He seemed to be sus- pended motionless in mid- air. But not for long. Suddenly a gale of wind caught him and carried By Lieutenant C. P. McDarment Lieutenant John Wilson, who at a height of four miles stepped overboard from an airplane into space. his parachute opened, he dropped for some distance through the air like a rock. liking for dangerous adventures of this kind, his friends call him ‘‘Dynamite Johnny”’ 63 celestial whirlwind into which presently fall like lead for hundreds of feet. Before Because of a noticeable Freezing gales in the thin at- mosphere tossed Lieutenant Wilson about like chaff. Some- times he spun on the edge of the vortex of a mighty whirl- wind into which he would drop 4 him many miles at great speed; then another gale, blowing in the opposite direc- tion, caught him and blew him back.as rapidly. The winds appeared to be inaturmoil. The parachute was banged around at all angles. It was even turned over so that it “looped.” Sometimes he would find himself spinning on the edge of the vortex of a mighty he would Only Seventeen Minutes! At last, suffering from nausea, he reached the steadier winds around five thousand feet: second toward a clear field, in which he made a landing. to make the descent. long minutes,’”’ says Wilson. After checking up the self-registering At three hundred feet he.opened the parachute, and began working It took just seventeen minutes “They were extra instruments that were car- ried aloft sealed, it was found that the exact altitude was 19,861 feet. This was a few feet less than was intended, but it broke the world’s record by more than a mile. The extra mile was the mile in doubt. It had been ques- tioned whether a parachute would open at that altitude. Except for a nausea that soon wore off, the lieutenant did not suffer physically. “Why did you take two parachutes?” asked someone. With a twinkle: ‘One might have worn out.”

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be turned out under pressure in one day \ HAT becomes of the ashes-and cin- ders that every morning you shake out of your grate or furnace? What becomes of the piles of slag accumulated in the “ vicinity of iron or steel 4% works? These and other waste materials can be turned into’ valuable building material if a plan that has been lowed. bricks During the shortage in building material it was discovered in Europe that waste, such as cinders, slag, lime, and coal, from which the gas has been extracted, can be pulverized and compressed into bricks. Combined with certain hardening sub- stances, they furnish excellent six-pound bricks, smooth-faced and porous. The bricks from waste can be made rapidly, the product of one plant being more than thirty-seven thousand bricks a day. When one considers the amount of waste accumulated around gasworks, furnaces, and other industries, the value of the waste utilized in making bricks can be realized. Making a Trailer of the Airplane ERE is a miniature airplane that can be towed through crowded eity streets without interfering with traffic. The airplane is designed to be folded down rapidly as well as to be quickly made ready for flying. When folding down the airplane for transport, a wooden stay pressing against the keel pin is loosened, after which the horizontal rudder is swung upward. By turning a handle at the top of the tightening tower, the cables of the supporting planes are loosened, allowing the planes to be removed. The bricks made of cinders are smooth-faced and and blow, one bub- porous. Thirty-seven thousand of these bricks can ble will come out Houses Built of Cinders bottom. ! Here is a house finished with concrete started abroad is fol- over the outside of the cinder-made IPES for bub- ble-blowing are now specially made. One of those shown herewith is so con- structed that it will blow two bub- bles at the same time. Instead of being bowl-shaped, the end of the pipe is shaped like a tea-strainer. When you wet the end with soap-water of the top and an- other out of the But there is another blower that eliminates even the bowl of soapsuds. It is a tube, open at both ends. In one end you fit a specially prepared tablet of soap which has a hole in the middle. You SOAPS In our youth we were glad to have a penny clay pipe for bubble-blowing; the modern child demands a pipe that blows two bubbles i Popular Science Monthly Two Bubbles at One Blow { pril, Ro. H' tractc¢ stretc fronte lem, tr ick ti elr | Th wide. n ake sider Then Th broug work place twist load. the \ tract turnt 4 blow through the other end. All you need do to pro- duce a bubble is wet the tablet of soap. When one tablet wears out, you insert another. The tablets are made so that they will expand after they have been inserted, and fit tightly. First the right kind of soap is made; theni Jis artificially dried and broken up; next it is combified with pow- 4 . . areas oe ae . dered sugar and olive-oil soap containing caustic soda. “ec Fred Telgord Wear. a Badge and Save Intieductions DON’T remember your name,” § 1 “you stammer, as you try to intro- duce two fellow delegates at the con- vention you are attending. The man Sh t Philedelphia. Pa. mumbles-his name; you don’t like to ask him to repeat it and you continue — to talk, not knowing to whom you are N talking. Should you meet again, you revo would have to repeat the process. hanc Would it not be better if each delegate Be guar wore some sort of identification tag? keep Introductions would then be unneces- As Sary. r face, ———— Strangers attending conventions will B dou} You d+ ait haus Oo Seckemther find it easy to get acquainted with one diag names at conventions where the another if they wear the identification T delegates wear these badges badge shown in the photograph. the | whe! ther You azo enor Ci that the: you dow time But When the wings are folded back, they will not exceed the width of a dow motor-car’s chassis. A strut is inserted into a clip at the rear of the motor wou 64

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i 1 to for lern shat pro- | one pand First “ially pow- soda. ” me, intro- - con- . Man ke to tinue yu are 1, you ocess. legate | tag? neces- 1s will sh one ration { pril, 1921 Road-Builders Make Use of the Turntable ] ERE is the idea of an ingenious contractor. Like all other con- tractors who undertake to build long stretches of concrete road, he was con- fronted with the transportation prob- lem, particularly that of turning his trucks about after they had deposited their load of wet concrete. The road was only eighteen feet wide. Even his little trucks could not make this sharp turn without con- siderable trouble and loss of time. Then came the idea of a turntable. The turntable was made and brought to the scene of action. It worked like a charm. The cars were placed, two husky men gave them a twist, and they were off after another load. Congestion was prevented and the work was speeded up. A small tractor is kept on hand to pull the turntable forward as the road grows. 4 A load of copra is sucked into a big pipe from the ship and shot into box-cars The air pipe that feeds on the ship’s cargo, carrying it away to box-cars waiting on a_ side track near by Turning a truck around ina hurry. Witha road too narrow for rapid turning, a turntable is used Shave with Revolving Blade OW there appears a razor whose i blade is circular and made to revolve by means of a spring inside the handle. The blade is protected by a guard that rests against the face and keeps the skin taut. As you draw the razor across your face, the revolving blade is given a double motion. Thus it cuts each hair diagonally. The jerking and pulling caused by the straight razor stroke is eliminated when the circular blade is used, and there is no skin soreness afterward. You can work rapidly with the new razor and ‘“‘once over’ should be enough. Compare the act of shaving with that of cutting bread, and you will see the merits of this razor blade. When you cut bread. you move the knife downward and diagonally at the same time; that’s how you get a clean edge. But should you try to cut a slice by downward pressure alone the bread would resist and the edge cut would be ragged. He is shaving with the revolving razor. It has adouble motion, insuring a smooth, quick shave The revolving blade is actuated by a spring inside the handle, and is protected by a guard that rests on the face and keeps the skin taut 65 Unloading Ships by Air HE old hand shovel is losing its place in industry. The endless belt-conveyor and the compressed-air system are fast replacing the back- breaking shovel. Now they are using compressed air to unload ships at Oakland, California. Several big pipes are brought on to the ship, the heavy compressors are started and tbe load begins to move shoreward at a lively rate. It is lifted high in the air, shot over the railroad tracks and building into freight-cars on the siding. The cars are pulled away as fast as they are loaded. The pictures show copra being sucked into the big air-pipe. It is the duty of the two men in the lower picture to guide the pipe and keep the material loose, so that the pipe can pick it up and whisk it away to the waiting cars. Air under pres- sure travels very fast, in some cases even reach ing a speed of several miles a minute.

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Aa prt Popular Science Monthly Do It with Tools and Machines to Get the Most Efficient Results T } r=] x \ Oo! din \ € arly \, glass. ¥ burns tissue aes Th with over ' The | This little drill has One man may exert des an automatic fric- a lifting force of ey tion and ratchet four thousand X-ray feed. It saves time pounds with this tube that would be jack. It has no of b otherwise _ con- bearings, gears, or ordin sumed in adjusting pulleys and weighs from the feed of the drill. but seventy pounds. It also helps to save When castings are made, the heat of the molten metal It is manufactured the drill points bakes the sand core into a solid mass. These compressed- of forged steel air tools dislodge the sand in short order Son W straig remo they whic] SCTeW Me ful re trace ofak as a piece screw are ( screw The draw-shave and the This heater keeps the Taking the place of a A bearing can be _ bab- t} rasp are out of date now. tools hot that are used to hook, this clamp will bitted in a jiffy with this with This electrically driven finish the edge on your grip metal sheets and tool. It is especially de- brass edge trimming machine shoes at the shoe factory. plates. It bites into signed to re-babbitt con- sized works faster and better. The tools are placed in them and automat- necting-rod bearings for It consumes little power the holes ically releases itself automobiles. Wooden and requires absolutely mandrels of different sizes no skill to operate are supplied with it M. bi purp wire both air al be di perat In not n fan Yr CO plane th A vise that has a handle attached to it so that This hood over the sol- dering copper carries the machinist may drill away all dangerous calle small pieces without fear fumes and protects the luste: of their turning around operator from lead poi- malle with the drill. It pre- soning. A suction is cre- Th vents battered knuckles ated by a motor fan Auer An electrically driven rubber that does the work of three waste men. It puts a piano polish on wood and has only to. be allow guided over the surface 66

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of id Lis no or is. Apri, 1921 Keeping Up with the March of Science Facts for the man who wants to know This Glass Is Half Lead \ ae cannot pass through -lead. 4 They do, however, pass through ordinary glass with perfect ease. The early X-ray tubes were made of. ordinary glass. As a result, many people received burns by exposure to the rays, which are tissue-destroying. The new Coolidge X-ray tubes are made with a glass that contains considerably over sixty per cent (by weight) of lead. The glass is fully transparent, but slightly dark in color. It is almost opaque to X-rays and a person may stand near the tube while it is operating, with little fear of being burned. A small window of ordinary glass allows the rays to escape from the tube. Screws Made of Beef Bones HEN the front and rear joint ends of beef bones are cut off and the long straight portions of the bones are boiled to remove the marrow and animal tissues, they become suitable material _from which can be made the most remarkable screws. Modern surgery can make such wonder- ful repairs in broken human bones that no trace of a fracture is left. The broken ends of a bone are sometimes spliced and jointed as a carpenter would fit together two pieces of a plank. It is here that bone screws are used. The strips of beef bone are cut roughly to the diameter of the screws and arc put into a lathe-chuck, and with a high-speed tool used for cutting brass, are roughed out. They are then sized for threading. Both Heater and Tan MALL electrical heaters have been com- bined with electric fans for household purposes. The heater is attached to the wire guard of the fan and when they are both in operation, the fan blows the warm air about the room. In this way heat may be distributed more quickly and the tem- perature of the room will be more uniform. In the hot weather, when the heater is not needed, it may be detached so that the fan may be used alone. Matches of Iron & 1803 a new metallic element was dis- covered and named in honor of the planetoid ‘‘Ceres,’’ which was discovered in the same year. This rare earth metal is called ‘cerium’ and it resembles iron in luster and color, but is soft, tough, and malleable. The gas-mantle industry, founded by Auer von Welsbach, produces cerium in its waste products, and from the cerium, a. joyed with iron, a new kind of match has been invented. It is literally an iron match. It strikes sparks; it is familiar in pocket-lighters. By turning the little wheel of the lighter, a spark ignites an alcohol wick. The iron match, which takes the place of a whole box of matches, is safe and economical. These pyrophoric matches were used in the trenches during the war. They promise to become a popular substitute for wooden matches. Do You Want More Food? iv you do, your reasons should be scien- tifically sound. A man’s energy expenditure in his work is a measure of the food he needs. A calorie is taken as the unit; it is the heat required to raise 2.2 pounds of water from 15 degrees to 16 degrees C. The number of calories in a food mass may be measured by burning it in a steel chamber known as a calorimeter. The sedentary worker requires about 400 to 600 calories. The heavy worker may need 2000 calories. In addition, there is an internal expenditure for the average man of 1700 calories. For two cents you can purchase about 100 calories of cheese, 200 of sugar, and 400 of bread. For a family the figures mount high. Are Potatoes Too Dear? OW much does it cost to get potatoes from the farmer to the final con- sumer? The cost is not known. Estimates have been made from time to time, but they were—just estimates. It is only recently that the Department of Agricul- ture has decided to get facts. A committee nas been formed to find the cost of bringing potatoes from the field to the table. It is a bigger problem than most people think, Wages, transportation, waste, storage, crating, etc., enter into the calculation. Tooth Solvents for Dentists OOKS as if all the joy of life were going to leave the dentist: He isn’t going to be able to use his best instrument of tor- ture much longer. Instead of boring out teeth in the usual painful way. he will use a ‘‘tooth-solvent.”’ This is an acid of organic derivation that will dissolve the decayed portions of a cavity. Simply by dipping a tiny swab in the liquid and applying it to the surfaces to be removed, both dentine and enamel can be painlessly taken out. It has been estimated that this advance will reduce the cost of dentistry something like fifteen per cent. Who can estimate the number 01 persons who will now cheerfully submit to dental work? 67 Wealthiest and Biggest HERE are now nearly six million peo- ple in the city of New York, and it is the largest center of population on the globe. It is growing faster than London at the rate of nearly two to one; London doubles its population every thirty years and New York every eighteen years. New York’s cash balance demands a sum of more than thirty million dollars, and it is the wealthiest city in the world. In fact, its total assessed value is greater than all of the United States west of the Mississippi, and its income exceeds that of twenty states combined. Every nineteenth American lives in New York city, and one tenth of all manu- factured products is made there. There are twice as many theaters in New York, and three times as many hotels as are in London. Glass that Heat Can’t Break RDINARY glass is very sensitive to temperature changes of a _ sudden nature. A drop of water on a hot lamp- chimney is very apt to set up strains that will result in instant fracture. A glass is now manufactured that is ab- solutely immune from sudden temperature changes. Two semi-metallic substances enter into its composition that have differ- ent points of expansibility. A tube is made from each of the two glasses. The tubes are then placed one within the other and fused together. A very rugged glass results. A Tribe that Eats Its Dead | URING a recent expedition into Africa, into the country lying west and north of Lake Victoria Nyanza, John Roscoe, lecturer of Cambridge University, made some interesting discoveries. He found some tribes who ate their dead, no matter what the disease that took them off. Even smallpox victims were not considered un- wholesome, consequently this particular tribe was one of the unhealthiest in the country. The Ghost of a Ghost EVERAL telephone or telegraph mes- sages can be sent on the same wire. This is called use of a ‘‘phantom”’ line. This theory is now being applied to wire- less. But wireless has no “‘line,” to start with. Thus we have the phantom of some- thing that is really non-existent: the ghost of a ghost! For incoming messages the system is to have several receivers, each of which can be ‘‘tuned” to a separate wave length agreeing with that of the sender. Outgoing radiations, however, require

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great application of energy to the antenne. Difficulty of duplication has always been that only a destructive conflict is set up by applying more than one source of oscilla- tion. There is now being developed a series of inductively connected electric ‘‘vibrators”’ that will make it possible to send as many as one hundred long-distance messages from the same radio set. Oil from Earth and Sand IL-GUSHERS flood the surrounding ground with oil. It forms small lakes and pools and it is taken from these and placed in barrels. When the oil is allowed to stand for a great length of time, some of it soaks into the ground. Experts from the Bureau of Mines have been considering the advisibility of recover- ing this wasted oil‘from old oil-producing sections. From data collected, it is esti- mated that 2,359,100 barrels of oil, valued at more than $3,500,000, could be obtained from the oil-saturated sand and earth about old oil-wells. Timber Preserved by Damp Ser timber will last for centuries when itis buried in water or wet sand. Oak piles that were constructed for Roman bridges nearly two thousand years ago have been found intact. In a gold-mine in Australia, at a depth of three hundred feet, pieces of oak perfectly preserved and hav- ing the appearance of having been sawed by man were found recently. The timber is in the site of an ancient river-bed. The tough fibers of the wood evidently are strengthened and preserved by the moisture they absorb. Many other kinds of timber would rot in water, and thus would soon be lost. The Tipless Shoelace HE metal tip comes off a shoelace invariably when one is in a hurry. Why not get rid of the metal tip entirely? That is done in a new invention brought out by Dr. Bibard of Paris. His lace is made entirely of silk, the end twisted so tightly that no metal tip is required. To accomplish this, a special machine had to be constructed. The machine winds the silk thread tightly around the end of the lace, making a tip that is as serviceable as one of metal. It will not come off. Longer Wires of Aluminum LUMINUM wire is used on _ high- + tension electrical transmission lines because it is light in weight and offers com- paratively little resistance. It is cheaper than copper and being lighter, longer spans between the poles is possible. This means fewer poles and a consequent smaller in- vestment for a long-distance power line. Still longer spans with aluminum wire will be made with the new steel reenforced aluminum wire that is now manufactured. Doctoring Sailors by Radio HE Seamen’s Church Institute of New York has established a radio service to aid in the treatment of men who become dangerously ill aboard vessels that do not carry physicians. A powerful radiophone outfit wili be in- stalled and the physician on duty will give verbal directions to the first-aid man aboard the ship. The request from the ship will be re- ceived in code, since freight vessels have not as yet been provided with radiophone equipment. However, the ordinary radio receiving outfit is sensitive to radio voice transmission and the answer to the distress call can’ be made verbally, thereby saving time and insuring greater accuracy. One Assistant: $225,000 if Rcersiaibe what New York state paid last year. But the assistant wasn’t a human being. It was a tiny piece of radium. Radium shoots out particles of matter at velocities up to 160,000 miles a second. This violent discharge is used to destroy or dissolve the diseased tissue of cancers and tumors. A single ounce of radium contains suffi- cient total power to,lift ten thousand tons’ a mile from the earth. A lump the size of an automobile could operate an ocean liner’ continuously back and forth across the Atlantic for two thousand years. If a ton of radium could be collected in one spot it would be impossible to approach within six feet of the mass without instant and agonizing death. When Is Current ‘‘On’’? T is difficult to tell when the current is turned on or off in the case of flatirons, percolators, and other electrically heated devices. An ingenious inventor has produced a device that will indicate whether or not the current is on or off. When the current is turned on, a small electro-magnet, which is connected in series with the device operated, is excited. This draws down a small armature, which is connected with a pointer on the outside. The pointer reads ““On’”’ when the magnet is excited and ‘Off’ when the current is not flowing. Where Did Life Originate? HERE and when and how did life as we know it on our planet, the earth, originate? These problems have occupied the minds of the greatest thinkers, the scientists of all ages; but a definite answer to the question cannot yet be given. Some modern scientists believe in the possibility of biogenesis or autogenesis, and defend the theory that life originated at an early period in the geological history of our planet in a manner not yet explained; that all organic life developed by slow steps from the original protoplasm; that at first the simplest one-cell organisms were formed, 68 Popular Science Monthly which in the course of evolution developed into higher and more complicated organic complexes. Other scientists refuse to accept the theory of the spontaneous origin of life on our planet, and maintain that the germs of life were carried here from other worlds, together with the cosmic dust that is known to be deposited on our planet at different times. They do not explain how life could have originated on some other planet while, in their opinion, it would have been impossible for it to originate on the earth. Svante Ar- rhenius has pointed out that the spores of bacteria are so small that it is quite possible that they may be carried from one planet to another. In twenty days they could cover the distance from Mars to the earth, in fourteen months from Neptune, and in nine thousand years they could reach Alpha Centauri, the sun nearest to our solar system. But granting, for the sake of the argu- ment, that these spores could be trans- ported through space and could endure the terrific cold prevailing in the interplane- tary space—273 degrees, or absolute zero, and would not be destroyed by the total absence of moisture and the effect of the ultra-violet rays, the theory still seems to stand on a doubtful basis. It is extremely doubtful that the germs of organisms, specialized in their structure to fit a limited range of conditions, could gain a foothold and continue to live under conditions that probably are entirely different from those on the planet from which they came. Shocks Restored His Sight ONE English soldier, who had been blinded at the battle of Ypres, re- covered his sight by nervous shocks. The first thing that startled him was a cat that jumped across his bed in the hos- pital. After this incident, he found that he was able to see slightly with his left eye. A few days later, he accidentally walked into the Thames. The second nervous shock partly restored the sight of his right eye. The physicians of the hospital were amazed. They decided to give the man electrical shocks from an induction coil. After several treatments, the man could see perfectly. Trapping Air in Food ERATION is the process of entangling air with food. For instance, when a housewife beats the white of eggs, she mixes up a certain amount of air with them that makes them foamy and fluffy. The same thing happens to cream when it is whipped. A little electrically driven machine has been invented for the perfect aeration of food. A hollow shaft bent slightly at the end is attached to a motor-shaft. This revolves in the food to be aerated. As it revolves, centrifugal force causes it to throw air off into the foodstuff. This keeps a stream of air passing down the shaft into the food. 7 I t t c f s I

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April, 1921 Housekeeping Made Easy It’s the little things that count in the home n f | — 2 n t e n e pf e t d l, n r 0, oe % oe ise This realistic little Chi- ee - nese figure carries his lan- This jardiniere has an ; mae ae A centerpiece for the breakfast-table that is use- ‘nisi ak sess aalie one e cense comes in powder ful as well as ornamental. It comprises candle being used to store water. a form and in small cone- lamps, a percolator, and a toaster Tubes in siphon shape ) shaped pastilles, and is carry the water to the al pleasantly pungent | ‘ =e growing plant e ‘0 y 3, d d 1s m 'y ; By attaching this drainer to the kitchen on hydrant and turning on the faucet, thus e- creating a vacuum, it is easy to suck out water from a wash-boiler or tub a S- at Smoldering cigars can make re. fastidious noses very un- od comfortable. This smok- us er’s tray contains a tube ht that snuffs out the light ex- peditiously and odorlessly re an A good housekeeper is A kettle handle has been il. known by the shininess of invented for protecting the ld her stove. A way to elimi- hand. It carries a shield nate grease collecting there- wide enough to save the on is to burn it off with hand, even if the lid should a plumber’s gasoline torch fall off ng ia she ith fy. 1 it has of the a , his Everybody knows how pap eg. eae “we sit comet watenger be- ment may be used with me comes. There is now ae x b : a ith Sy a wallpaper with a per- i ee ee his fc-ated edge, which is Why waste the warm air from This attachment for the electric one hand. This com- the k: ocked off before the the boiler heater? Here is a ring iron leaves no one in doubt as to bination would also be rc 1 is opened that fits around the boiler, from whether the current is on or off. useful to campers which you can hang towels or A small black indicator points kitchen utensils to be dried to “Off” or “On”

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Forerunner of the Sextant— the Astrolabe HE great-grandfather of the equatorial telescope is the as- trolabe, literally a ‘“‘star-taker.”’ With it the Arabs took the posi- tions of the stars, the height of mountains, and the latitude of a place. They also found the alti- tude of the sun, the moon, and the stars with the astrolabe. It consists of a disk whose mar- gin is engraved with the divisions of the circle, and around which a Popular Science Monthly ROTATABLE ~ S-PART HOLDER * Do Knurling with This New Tool D° you know what a knurling- tool is? The handle of your safety razor is knurled—fine lines are cut into its surface. This is done with a knurling-tool. The ordinary knurling-tool is capable of making only knurled lines with one degree of fineness. This tool will produce several lines of different depth by simply turning the holder around so that a differ- ent set of knurling-wheels will come pointer, or “sighter,”’ is rotated. When the pointer is sighted at one star and then at another, the angular distance in the sky between these stars can be found roughly. Cleaning Castings with Sand N ingenious machine is used to clean + castings by blowing sand on them. Ordinary sand is a real abrasive substance. We realize this when we think of sandpaper and its cutting power. Don’t think that the sand is blown on the castings gently. Not by any means. A terrific pressure is used. Compressed air picks up the sand and carries it to the castings in the big steel barrel, where it is flung against them with great force. The sand and air are admitted to the barrel through the pipes. The rough cast- ings are tossed about within the barrel, so that the sand will reach all parts. The metal is clean and bright when taken out. Dangerous Sledding in Switzerland Ww do so many people go to Switzer- land for the winter sports? For many years it has been the playground of Europe, but every year more and more Americans are finding it to their liking because the steep mountain slopes there are sure to be covered with snow for the greater part of the winter. In the picture above you see a sled taking one of the sharp turns on the post- road near Davos. This road is the finest natural run in Switzerland. The curves, as you see, are banked at very sharp angles. Great skill in handling a sled is necessary in order to steer it safely past these curves. The sled shown in our illustration is travel- ing at an angle of at least sixty degrees. Why don’t the riders fall off? For the same reason that milk will not spill out of a pail when you swing it rapidly in a circle centrifugal force. into position. The knurling-wheels are made of very hard steel. As they rotate against the piece to be knurled, they sink into its surface. Two Cuts at One Time UCH a milling machine as the one printed below is really taking the place ofaplaner. It is surfacing the entire side of a large automobile crankcase in a single cut. Not only is it doing this, but it is also surfacing the bottom, since two large cutters are at work. One revolves in a horizontal plane and one in a vertical plane. The vertical cutter can be seen at the left of the picture. Many hours are saved on this operation by the use of these large milling cutters, time-saving that was not possible a few years ago. © Ewing Galloway —— © Key Rec AR 4 n bile di a red each ‘ shown dents safe s] island but o1 that | poiso! The are OF aS al lights has ju Dt } Well, metal A ¢ made tracin the p hydrec narro five-i2 sinks opera has b As mach hours throu Vv ith

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w—eelUhwCOUOOUUND Ww € oS welll Oe —_— =

Apri, 1921

4

© Keystone View Company Red Lights for Safety Islands A RED light usually means danger, and 4 most people—even reckless automo- bile drivers—will heed it. In consequence, a red light has been placed at the end of each “safety island” in San Francisco, as shown in the picture above. Several acci- dents had occurred in these supposedly safe spots, and drivers complained that the islands are hard to see at night, which is hut one more instance of the old proverb that “fone man’s meat is another man’s poison.” The red lights that now decorate them are on the regular street-light circuit, and as a result go on and off when the street lights do. A notable decrease in accidents has justified their instalment. It Cuts as It Traces ID you ever draw pictures with a pantograph when you were young? Well, this oxyhydrogen torch cuts duplicate metal parts in the same way. A drawing of the part to be cut is first made to the proper scale and placed on the tracing-table of the machine. In place of the pencil, the pantograph carries an oxy- hydrogen torch, which spits forth a hissing, narrow flame that cuts through a piece of five-inch plate just as a hot table-knife sinks through butter. A small motor operates the device automatically after it has been adjusted. As a labor- and money-saving device, this machine is a hard one to beat. It saves hours of time on a single job. It will cut through metal several inches in thickness with perfect accuracy.

a aie oD @t

The Vacuum Bottle in the Sick-Room HE vacuum bottle that you take with you on pleasure trips will also serve you well if there is serious illness in the family. Everybody knows how difficult it is to keep a flaxseed poultice—for example- hot for any length of time. The vacuum bottle will enable you to maintain the proper temperature of a wet dressing of any kind. The bottle is tied upside down to the bedpost and a rubber tube is attached to the opening. The liquid at the proper temperature flows down the tube to the compress attached to the tube. A spring letter-clip, clamped on the tube near the compress end, regulates the flow. If the patient is not entirely helpless, this transformation of the vacuum bottle from pleasure to business, as it were, will enable the usually busy attendant to be about other household matters.

Piano Wire Helps Astronomy INE wires placed across the lens of a Harvard observatory telescope and forming a screen are there for a purpose. The screen forms a diffraction grating over the lens, producing ‘‘secondary images,”’ really small spectra of different sizes and distances from the principal image of a star. It is possible to compute the amount of light that forms these images, and to derive from the results the relative photographic brightness of the stars. By comparing these with fainter stars, it is possible to extend the scale of magnitudes from the brighter stars, whose brightness is known, to fainter and fainter stars, whose magni- tudes are desired.

Pumping Air into the Lungs F a man falls into the river and is dragged out apparently lifeless, or if he comes in contact with a live wire and is apparently dead from shock, there is just one thing to do quickly. Get his lungs back to the business of breathing. There are various ways of accomplishing the result. <A ‘“‘breathing-machine” has been invented to restore automatically the respiration. Try taking forced deep breaths for about three minutes and your lungs become tired. For forty or eighty seconds you may have no desire to breathe. This fact has been utilized in measuring the volume of air involved in the experiments tending to produce the best results. When the “‘breathing’’ mechanism is in a state of complete collapse, only outside mechanical means will bring about a nor- mal condition.

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Feed Coal to the Fire in Bags ft ERE’S a new way to ‘‘keep the home fires burning”’ in fireplaces without creating the usual shoveling noise. Pour your coal into paper bags, some day when you’ve nothing else to do. Then, when guests arrive and you wish to start a fire, quietly place one of your bags of coal on the grate—no noise, no dirt. The bag burns and releases the coal, which then spreads over the grate auto- matically. This is a very good household hint, to be passed on to the housewife. Cleaning Streets with a ‘*Three-Wheeler’’ LEAN streets help to make healthy cities. This little three-wheeled truck with its revolving brush will help to make it easier to scrub and brush off pavements. _The power is transmitted to the single wheel in the rear of the truck by a fifteen- horsepower motor located under the hood. The revolving brush obtains its power from the same source, and it is connected to the gear-box by a shaft with universal joints. The little truck can turn in a very small circle, which is necessary when it is at work on narrow streets. A decided advantage of this efficient little machine is that the sweeping brush can be very quickly changed and a scraper, a squeegee, or a snow-plow put in its place, thus making it adaptable for all kinds of weather. Up Goes the League of Nations’ Radio Tower RADIO tower, two hundred feet high, put up in fourteen days! This happened at Geneva, where the members of the League of Nations had their first meeting. The engineers arrived on the scene, and this steel arm started to shoot into the air at the rate of fourteen feet a day. When the first day of the League’s work was finished, the world was informed of the transactions by radio. A powerful portable equipment was set up at the base of the tower, and this flashed the news broadcast. Thirty years ago it would have been necessary to stretch miles and miles of telegraph wire, and it would have taken the world hours to learn the news where it now takes minutes. Popular Science Monthly Ice-Bags from Old Inner Tubes ig ante eens relieve the feverish patient, but they are not large enough to cool his entire body. An old inner tube will do a much better job. You cut the tube at the place where the valve is. located. Remove the valve, tie one end of the tube tightly, and fill the tube with ice. Then tie the other end, and you will have a long narrow ice-bag that may be placed at the side of the patient or even wrapped around him. ; Old inner tubes are one of the most versatile of cast-off automobile parts. ‘*Hold-Ups”’ in London in Aid of a Hospital Not long ago the medical students of — one of the hospitals organized to make a raid on London to collect funds for their hospital. To do this, they dressed in their white ‘‘overalls,’’ much as they appear in the operating- or dissecting-room, armed with all their appliances of surgery and medicine. In this grotesque garb they halted people on the public thoroughfares and ‘‘tested”’ their hearts with a stethoscope, finding out whether each person had a good or a bad heart. If the heart was sufficiently good to further the cause, the money was cheer- fully given. If the enterprising students of all the hospitals in London undertook the task of holding-up pedestrians, a good opportunity would be afforded to find out how many ‘“‘go0d hearts’? there really are in a city. ey ra \ : Oy. HONEY i* os Power g TOU the Charli never | dead passes accour lost or An there family quarte Ceci Bertill will cl they v him. How Ber A™ Ss! the m the bi try. In 1 is hau carts from § miles miles. lives from much to the port i to Nev In the eo work avera; ton m

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of ke sir ir ed nd le i ut ad od the of ity iny April, 1921 Cecil Is Fingerprinted 7OUR grandfather probably remembers the excitement that was created when Charlie Ross was kidnapped. Charlie was never found by the police, and he may be dead by this time. Hardly a month passes but the newspapers print an account of some child that has been either lost or abducted. An anxious mother has decided that there shall be no Charlie Ross case in her family. She took Cecil to police head- quarters and had his fingerprints taken. Cecil was also measured according to the Bertillon system, but the measurements will change so rapidly, as he grows, that they will be of little value for identifying him. The fingerprints are good for life. How Motor-Trucks Benefit a Nation | gscraengelogree seldom stop to think what the motor-truck means to the business of the coun- try. In the Argentine grain is hauled in horse-drawn carts at a rate varying from $1.40 a ton for three miles to $3.40 for fifteen miles. A farmer who lives twenty-five miles from the station pays as much to get his produce to the railroad as to trans- port it from Buenos Aires to New York. In the United States the cost of doing the same work with motor-trucks averages fifteen cents a ton mile. Fishing on Horseback HE shrimps that live in the waters of the North Sea not far from Ostend, are the choicest in the world. They are eagerly sought by the restaurant-keepers of London and Paris. Yet the fishermen who gather them use the same methods that were in vogue in the days of the Roman occupation. As the tide comes in, the beach is dragged for miles by fishermen mounted on horses. They pull behind them huge nets that are fastened to triangular metal frames. Poles attached to the frames help support the nets. Ropes connect the frames with the horses’ saddles. Thus, as the horses move slowly through the water, they drag the nets behind them. Whisky Hidden in Dish-Water .« HISKY is dumped into dish-water whenever a revenue Officer enters cer- tain saloons. The whisky is kept in a box beneath the bar. The lower rear edge of the box is hinged to the front of the bar; the only other support it has is a latch that can be opened by merely pulling a string. Be- neath the box is the wash-tub into which used glasses are dipped. The “‘liquor’’ in the box is kept in ordinary glasses. As soon as the revenue officer is spotted, the bartender pulls the string, releasing the latch. The box tips forward, and the filled glasses fall into the soapsuds. We don’t publish this as an aid to liquor- dealers who violate the law (they need no education), but simply to throw light on the question, ‘‘Where did he get it?” ‘Meet Me at the Notions’’ Bi et me at the notions, Mary.” Mrs. Brown sees her name and this announcement in the department-store “engagement book,’”’ and she immediately seeks out the notions. Other women do the same thing, and in this way the en- trance to the store is not blocked; but an- other instance of the adage that there are several ways of killing the well-known cat. The manager of the store placed this en- gagement book on the radiator near the entrance. When two customers arrange to meet each other at the store, the one arriving first writes a note to the second, and continues on her way. Do You Know What Quicksand Is? CCASIONALLY a spot on the sandy beach or on the course of a stream can be found where a man or a horse would be swallowed up It is a quicksand. Any sand can become quicksand if there is an up- ward inflow of water, and if the amount of water is sufficient to more than fil] the spaces between the grains of the sand. In construction work, where the movement of surface water is often interfered with, quicksands may be formed. The remedy is founda- tion work to restore ground water to normal level.

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Before you give your car a fresh coat of paint, you will have to remove the old paint. You will save time by using a little sewing-machine motor with sandpaper rings at- tached to the end of its flexible shaft LICENSE PLATE

SPRINKLER HEADS . t 4 Be 14 Paki dss <

Owners of Fords will ap- preciate the new license- plate holder shown here that does not interfere with the crank or the shock-absorbers Skidding is one of the dangers of automobiling and its prevention an ever- present problem. Here the suction principle is used to prevent skidding

Regulation of the openings in this radiator-cover, to suit variations in temperature, radial, triangular slots that may be closed by the pinwheel-shutter is secured by the New Accessories for the Owner of Motor- Truck or Automobile

WATER . we PIPE

Motorized circus companies and military bodies on long marches are now equipped with bathrooms on wheels. The body has the appearance of a.moving-van and is divided by a partition intoa dressing-room with lockers and the bathroom, which has eight showers with hot and cold water

To show the ease with which this rim is operated, the makers employ a one-armed man to remove a rim and put another in its place 74

A device for foiling the automobile thief consists of a steel cable inserted in the tubular bumper. Be- fore leaving the car, its driver wraps the cable around a front wheel, and locks it. Any attempt to start the car starts a bell ringing This spark-plug has a lens through which you can watch the spark and learn whether your gas mixture is right Popular Science Monthiy

Stripping a tire for re- treading or vulcanizing is accomplished in about fifteen minutes by this motor-driven aluminum cutter. On the periphery of its cutting-wheel are sixteen steel knives that are renewable j=,

LENS REMOVABLE

SPARKING = | POINT ~— -

One of the new automobile models has a pocket for small tools in the side door and a large sliding drawer under the front seat for the larger tire-tools

April OS. DH we 65 tH On tS 8 fw LLU a —_—=~ ~ as

|

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hiy = u l April, 1921 Do You Want Advice About Your Car? OUBTLESS you have received many a hint about the care D of your-automobile or motor-truck from the pages of the Popular Science Monthly. We realize, however, that special cases require special advice. We therefore invite you to send your problems to the Automobile Editor. If you wish to know more about the devices pic- tured on these pages, or if you would like special automobile advice of any sort, ask questions. You will find some inquiries answered on page 82. Fool-proof and of prac- tical design is a new electric heater that can be operated by wiring it to any electric-lamp socket. It may be used for keeping the engine and radiator warm in cold weather As a protection from dust and wind, automobilists in Paris wear leather hats likethis. These hats or hoods are ventilated and provided with inset frames into which white or colored transparent celluloid win- dows are fitted Another thief-foiling auto- mobile lock which, when locked, prevents the use of the steering-wheel. It is made in thirty sizes to fit different makes How the adhesion between the tread stock and the hard-rubber base of truck tires is determined. The force for separating layers is measured with a spring balance se ag HYDRAULIC The hydraulic shock-absorber here illustrated is incon- spicuous and can be installed on any car without requiring alterations. It has no springs 75 Waste and untidiness can be avoided where much lubricating nor straps oil is handled, by installing this storage-tank with hoist pumps Notches in the rim of the steering-wheel enable this armless man to drive. The hooks at the ends of his artificial limbs engage the notches Six inches of wire chain soldered to the inside of the cap of the radiator-filler pipe and provided with a wire anchor will prevent the loss of the cap This clamp for radiator hoses requires no screws. Itslever engages a notch, of which there are four, various sizes to allow for tubes of

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N spraying trees on a fruit-farm the motor-truck is filling a very useful position. Not only does it provide the means for moving the apparatus from place to place, but it also furnishes the power for the pump that sprays the liquid. The tank, pump, and spraying nozzles are demountable from the truck chassis. When the spraying work is done, the entire apparatus may be removed and an The entire outfit may be demounted from the truck and an ordinary truck body fitted on instead Popular Science Month, Spraying Fruit-Trees by Motor-Truck It carries the apparatus and furnishes power for the pump is driven by a power take-off at tached to the truck transmission, of the rotary type and will pum thirty gallons a minute against . pressure of three hundred pounds The excess capacity of the pum; not used by the nozzles is pumpe: back into the tank through jet located along its bottom, thereb: providing for the agitation of th spraying liquid. The spray pum may be operated eithe ordinary truck body fitted, so that the vehicle may be used for hauling. Because of the large horsepower of the truck engine that is used to operate the = spraying pump, the equipment is one of the fastest working sprayers ever offered to fruit-growers. With one man driving the truck and two others holding the nozzles, small trees may be sprayed at the rate of one hundred and fifty an hour. The tank in which the liquid is carried has a es REELS Meare GALLON while the truck is ir motion or is standing stil! All four truck wheel: are provided with flange to prevent the wheel from sinking in the sof! ground as it moves in anc out between the rows o trees. On account of the high pressure of three hun dred pounds that can bi maintained by the pump, the spray thrown by th: nozzles is exceptionall) fine. This means, of course, economy in the consump- tion of the spraying-liquid, which is an _ important item both asto the amount capacity of six hundred NE of the greatest causes of ex- cessive wear in the engine of the gasoline farm tractor is the fine dust drawn into the engine cylinders in the air vaporized with the fuel in the carburetor. Except in wet weather, the tractor is almost continuously en- veloped in a haze of dust-laden air, and yet it is from this air that the car- buretor has to draw for making its explosive mixture. This evil always will be present in power farming, where the tractors are run at a fair rate of speed. Dirt, when once in the cylinders, tends to score the cylinder walls, gum up the lubricating oil, and results in excessive wear of all the mov- ing parts. There have been many at- tempts to fit some sort of air cleaner on the tractor to remove this dust from the air before it reaches the carburetor and is mixed with the fuel. Some de- signers have employed centrif- ugal cleaners and others a water clearer in which the air is expelled below the surface of the water and forced to pass through it be- fore being led to the carburetor. Neither one of these devices, gallons. The pump, which place; Fresh Air for the Farm Tractor’s Lungs when used separately, has proved satisfactory. So it has remained for one of the large creeper-type-tractor manufacturers to devise a combina- tion system in which both the centrif- ugal dry-air cleaner and the water cleaner are employed. How this sys- tem is worked out is shown in the accompanying illustrations. The air drawn in through the radi- Air is forced through a centrifugal cleaner and a washing tank filled with water, where nearly all dust is removed ep 7& The tree-spraying tractor moves easily from place to it furnishes power for the spraying apparatus of solution used and the time consumed. The air tO be used in the carburetor is sucked in through the radiator ator by the fan is first forced past and through the dry-air cleaner of the centrifugal type. This cleaner takes about ninety per cent of the dirt out of the air. This partially cleaned air then goes up through the intake pipe of the water cleaner (mounted outside of the engine hood, a: shown in the illustration) and down below the surface of th: water. It then rises against th« series of two baffle-plates tha’ tend to separate the particles o! water from the cleaned air s that the entireiy clean air fed t: the carburetor is moist and yet not fully saturated. TREMgc Ae April, STE ANE TUE A sc ica Tuc inst for tles oil ' gine Ty T is go" horses it is a that 1 absen the ca The is on Ordnz that ¢ take © about conto tion t in co creept spring the gi roller: of the

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1921 Whistling for Water O warn the motorist of an over- heated engine, a New York manufacturer has invented a device that is heard and not seen. The new apparatus works only when the water runs low in the radiator, and that remaining is turned into steam. Then a whistle is sounded—a siren that can be heard above all the din of the city — 3 .- | : ee ‘od i Mounted on a short arm on the left front fender, this apparatus combines a white light, a red one, and a mirror A Mirror by Day and a Light by Night ECAUSE every state requires that a red light be shown at night on the back of vehicles and a white light in the front and many states require that a mirror be mounted within sight of the driver so ly streets. 2 The indicator consists of a cylin- t drical barrel above the top of the ) L filler-cap, together with a tube that T IND CAGE extends from the interior of the 1} BE - barrel down into the top radiator- € tank. This tube is IT cut like a whistle, | and when the water J. A sort of mechan- : “ ailint : 7 ical Tommy in the Tadiator 1s e Tucker, which,: turned into steam, Is instead of singing the steam issuing 1 for supper, whis- through the cut in ’ tles for water or h b A : — oil when the en- t e tube gives a O gine gets hot whistle. ne The device serves : also as a water-gage. De Pp, he 4 . : Tractors in the Army a T is the intention of the United States A government to substitute tractors for ss horses in every branch of the army where ss it is at all possible. This means, probably, “ that the near future will see the complete absence of horses, with the exception of the cavalry. The tractor shown in the picture below is one of a series of machines that the Ordnance Department is developing toward that end. It weighs three tons and would take the place of six horses. Its speed is about that of a galloping horse. An interesting feature is the creeper contour of the roughest ground. In addi- voy Fog hk that he may observe cars approaching from the rear, a New York concern has brought out an accessory that combines all three functions. The apparatus, mounted on the left front fender, is made up of a cylindrical casing with a white lens in front and a red lens in back. Inside the casing is an electric bulb, which is wired up to the storage-battery. The casing is supported on ashort vertical arm, to the rear of which is also pivoted a circular mirror. “Watched”—to Make the Automobile Thief- Proof F the very great number of ‘Stop tion to the big wheels, there are four rollers : | mechanism, which is designed to follow the S| in contact with the lower side of each rollers, which press against the upper side of the belt. — : One of the many machines that the Ordnance Depart- ment is experimenting with, the object being to sub- stitute tractors for horses in the army ts This sign, re yoy einer eg thief’’ devices that have appeared in ° an automobile in e drivers ab- . é ‘ ‘ creeper. They are mounted on cantilever ence. acts as a watch-dog. It the automobile market in recent months springs and hold the belt in contact with would be difficult for a thief to and, owing to the increasingly frequent the ground. They are linked also to the cover the word unobserved robberies, many inventors have been devot- ing much time to the problem ~ nearly all depend on rendering inoperative some part of the mechan- ism. An automobile-thief trap recently invented by a New-Yorker, however, does not work on this principle. Instead, the owner or driver, when he leaves his car, simply pulls out a corrugated plate, thereby exposing the word WATCHED. Since the device is attached to the windshield or some other conspicuous part of the car, the theory is that a thief will pass by a car with this label in full view of every passer-by. The plate and its container are interlocking, and there are no duplicate combinations, hence only the owner’s plate will blot out the telltale word. It would be difficult for a thief to find a quick substitute covering or to paste anything over the word, and, even if he did, detection would be sure to follow. This invention is clearly based on a knowledge of psy- chology. Even a hardened automobile thief would have the sensation of a stern eye upon him as long as the card was in evidence.

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Popular Science Monthli; Helping the Motor-Truck Driver Consider him if you would get the most out of your equipment OOD drivers do not (5 simply ‘‘grow.”’ They are made. Assuming that the driver knows the mechanics of his business as to how to stop and start, change gears, lu- bricate engine and chassis, and load his truck body, there are many other things that the owner can do to help him get the most out of his truck. Many of the things that the truck-owner can do to make his motorized delivery satis- factory apply with equal effectiveness to the owner of one or two small trucks as to the owner of fifty ora hundred large-capacity trucks. But an increase in the number of your truck-drivers introduces special problems of super- vision. Assuming that the driver knows his business, he ought to be provided with certain conveniences that will enable him to give the best that is in him. These conveniences are: closed cabs; heated cabs; self-starters; special body designs for ease in load- ing and unloading; proper skids for handling heavy loads; other loading and un- loading means, such as cranes or derricks; platforms; and uniforms for drivers handling any goods that would make the wearing of a uniform at all feasible. Protection from Storms The closed motor-truck cab is following the develop- ment of the closed vestibule on the trolley-car, and for the same reason. The driver who is exposed to rain, sleet, and snow, who is soaked to the skin and chilled to the bone, cannot be expected to do his best work. It is against human nature. The damage does not stop with the poorer physical work done; it is transferred, in a way, to the truck itself. A driver who will not do his own work well will also not give his truck the mechanical attention it requires. The result—higher operating and maintenance costs, with a By Joseph Brinker Only the strongest can stand work like this. Give the driver and his helper all the aid you can in the shape of platform skids and other facilities Ask Us! RIVERS are the key to truck suc- cess. They can make transport- ation by motor-truck a success or failure. A good driver with a poor truck may show better results than a poor driver with a good truck. No machine is more efficient than the man who runs it. Mr. Brinker points out the part that the driver plays in getting the most out of the truck. If there are any questions that occur to you about motor-trucks, write to us. It doesn’t matter whether you own one truck or fifty.—Editor. Many types of devices for loading and unloading can be obtained. Here is a small crane that makes lifting easy 78 subsequent high cost of de- livery per ton, package, or other unit of measure. The use of heaters in truck cabs is another step in the right direction. Heaters can be bought. They utilize the heat of the exhaust engine gases to warm the air in the cab. A cab heater is an item of comparatively small cost, but of large influence toward making a warm, contented driver who will do good work and take good care of his truck. Save His Strength Self-starters make it pos- sible for the driver to do more work with less exertion. The increased use of starters has been most noticeable on the smaller sizes of trucks that are mounted on pneumatic tires. On such trucks the cushioning effect of the tires tends to prevent the truck vibration from damaging the electrical equipment and bat- tery. Self-starters save fuel. The driver will not shut off his engine during short stops if he has to crank it by hand. While the gasoline saved may be small at each stop, it amounts to a considerable amount in a day, a month, or a year. The larger the number of trucks in service with starters, the larger will be the fuel savings in the aggregate. Consult the Driver The body type is generally adopted without consulting the driver. He ought to be asked what kind of body will enable him to do his work quickly and well. Too often he has to make the best of a standard type of body when some small change, either in the location of the doors or the introduction of some kind of shelving, will greatly help the driver in loading and un- loading. No fixed rule can be given as to body types. A type of body eminentl) suited for one class of work may be entirely unsatisfac- od he" ; sami am nea fob Ssdtr April, tory f study under then meets condit Ski access the we his ph fagge atten’ truck, collisi loads, ried, lifting be még derric body barre with crane value at the possi! whicl with 2 and made the fl that ° lifted Whil made platf. inche most Ur respe his t1 work

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Mm WO Coe or DW W ~~ oe O et Ss © eh DM (D mo @ _ — ~ SCOP 4 SGA Pace tee Saeed bys a Apmil, 1921 tory for another. Make a thorough study of the particular conditions under which the truck must work, and then select a body that most nearly meets all of the peculiarities of those conditions. Skids Save Lifting Skids are another simple truck accessory that often help to speed up the work of the driver and make easier his physical tasks. A driver who is not fagged out will generally pay closer attention to the actual driving of his truck, and have'fewer accidents and collisions. When especially heavy loads, such as barrels, have to be car- ried, every attempt to avoid physical lifting on the part of the driver should be made. One way is to mount a small derrick or crane at the side of the truck body at the rear. With such a device barrels may be loaded or unloaded with a minimum of effort. Such a crane is, of course, of the greatest value for unloading on to the sidewalk at the points of delivery where it is not possible to set up a platform upon which the barrels may be rolled off with no lifting at all. _ At plants or warehouses all loading and unloading platforms should be made as nearly as possible level with the floors of the motor-truck bodies, so that the goods may be rolled instead of lifted into and out of the bodies. While little if any attempt has been made at standardizing truck-body platform heights, a platform forty-two inches off the ground will be level with most truck bodies now in use. Uniforms also play a big part in the respect that a man has for himself, for his truck, and for the firm for which he works. While the uniform is today used principally by drivers of depart- ment-store trucks, florists, and-jewel- ers, the psychological effect should be considered in uniforming the coal- truck driver, the contractor’s truck- driver, and others, with a uniform, even if it is a pair of overalls and jumper in summer and a heavy coarse pea-jacket in winter. Colonel Waring heightened the self-respect of New York street-cleaners by dressing them in snow-white duck. Street-cleaning ceased to be a dirty calling. A uniform makes even the driver of a coal-truck think more of his personal appearance. One large Pittsburgh .coal-dealer has gone so far as to equip his garage with This truck is fitted with shelves on which packages for retail tobacconists are stowed. Properly marked, it is easy for the deliveryman to pick out each dealer’s package In factories that furnish: lunches for their employees, the motor-truck drivers ought to be made welcome. Exposure to all kinds of weather makes hot food especially appreciated 79 . same ances Te addddddaais > ge te LLL Have you closed cabs on your trucks? When a driver is half cold he cannot drive carefully or attend properly to his truck a battery of shower baths, simply that his men may ride home clean at night and not be ashamed to ride in a trolley-car with office workers. The coal-dealer who introduced this plan considers it one of the most important advancements:he has made; his results have more than offset the cost by reason of- the greater contentedness among his men. ; The Driver the Key to Success All this, with the possible exception of the shower-bath idea, applies just as well to the man who operates only one truck as to the man who operates a hundred. These are fundamental principles. Human nature is fairly constant. The truck-owner should always bear in mind that the driver has in his own hands an expensive piece of mechanism, which, if treated properly and adequately equipped, will reduce transportation costs. Most of the day the truck is out of sight of the owner or superintendent. The driver, in the last analysis, is the real key to truck success or failure. As the size of the driver organiza- tion increases, the problems change, principally because of the loss of the personal contact between them and their superior and the increased diffi- culty of getting them all together at any one time for instruction or inspira- tion. When the driver organization is large, there is an opportunity for intro- ducing the competitive spirit among them as expressed by some form of bonus for good work, freedom from serious accidents and customers’ com- plaints, tonnage carried, fuel economy, or other factors. No one fixed bonus system can be applied to all trades. Bonuses may be offered for almost anything that means better trucking. The kind of work performed and the trouble ex- perienced with the drivers all have their influence upon deciding for what

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the bonus is given. But, no matter for, what the bonus is given, it will fail unless every driver in the crew has an equal chance to win the prize. Unless each driver gets a “square deal,” any bonus system is a failure. One method of making good drivers in a large fleet, after a concern has decided’ just what its drivers should and should not do, is to talk to them occasionally in large or small groups. There are two ways of talking to large groups of drivers, one by word of mouth, and the other by the printed word. For personal talks, the drivers should be assembled on company time and told what the company is attempt- ing to accomplish and how they should act and not act under certain condi- tions. Thisis perhaps the best method of driving home ideas on how best to operate and maintain a truck so that its life shall be long and useful. A small printed pamphlet is a materi- al help if the force of drivers is a large one and can not be conveniently operating conditions. These pamphlets may be in the form of bul- letins arranged to fit in a binder to be car- ried by the driver at all times. The con- cern’s house organ or magazine may also serve to stimulate the truck-drivers and make them feel that they are an integral part of the firm’s or- ganization and that they can do just as much to build suc- cess as the salesmen or the office workers. Don’t Bar the Driver from the Lunch-Room Where a large fleet of trucks is main- tained in a _ private Put the delivery truck- driver in uniform. It will give him greater respect for himself, for his truck, and Popular Science Monthly lunch-room facilities are offered for the mechanics, the same facilities should be extended to the drivers who return be- fore noon for after- noon deliveries. Truck-drivers appre- ciate hot lunches just as much as factory workers. Make them feel that they are es- sential parts of the organization, and they give better service. It should always be borne in mind that the driver is a human being; that he is en- trusted with an ex- pensive piece of ma- chinery; that praise given when due, re- sults in greater loy- alty and better service called together in a group because of service station, and for his firm rendered. Write to Us About Your Motor Troubles If you have a motor-truck or automobile problem, let the Automobile Editor solve it Why Kerosene Develops Knocks Q.—Will you please explain why the ordi- nary gasoline engine develops a_ serious knock when kerosene is used as fuel instead of gasoline?—L. A. P., Hartford, Conn. A.—A mixture of kerosene and air has a lower ignition temperature than a mixture of gasoline and air, and unless the compression pressure inside of the engine cylinders is reduced, the kerosene fuel pre-ignites, causing the engine knock to which you refer. Rates for Overland Hauls Q.—Using a 5-ton truck, how much should I charge a mile for a full load for overland haulage work on trips 100 miles long in each direction ?—J. H., New York City. A.—The average rate for such work with 5-ton trucks has been $1 a mile, or $100 for atrip 100 miles long. It does not cost $100 to run a 5-ton truck for this distance, but the rate a mile must include items for the cost of doing busi- ness and a profit for the truck operator, in order that he may continue in busi- ness. When such long trips are made, it is usual for the truck owner to en- deavor to obtain in advance a return load from the city to which the first load is delivered. If the Engine Knocks OQ l operate a 3 1/2-ton truck whose en- gine begins to knock on every cylinder when subjected to the slightest strain. I have ex- amined the bearings, the valve timing, the magneto, the spark-plugs, and cleaned out the carbon and yet have not been able to eliminate the knock. Could you advise me what to do?—H. H., New York City. A.—One of the causes of the trouble may be a too high compression pres- sure in the cylinders. If the engine has a detachable hood, the compres- sion pressure may be reduced slightly by inserting a \%-in. or a 14-in. gasket between the tops of the cylinders and the bottom of the cylinder head. This will increase the combustion space in each cylinder. This, in turn, will re- duce the compression pressure and may eliminate your trouble. How to Figure Grades of Hills Q.—To settle a controversy, will you please tell me what angle corresponds to a grade of 100 per cent?—T. D. P., New York City. A.—A grade of 100 per cent corre- sponds to an angle of 45 degrees. The percentage of the grade is the ratio of the vertical rise in feet to the horizon- tal distance traversed in feet. Thus, a vertical rise of 100 feet in a horizontal distance of 100 feet gives a grade of 100 per cent with the angle of the grade 45 degrees. When Pistons Are Worn Q.—How can I tell whether new pistons and rings are necessary for an engine which has low compression ?—J. K., Chicago. A.—If a thorough examination of the valves shows them to be in good condition and seating properly, an ex- cessive wear of the pistons and rings will be indicated by an_ excessive amount of oil on the _ spark-plugs. Another method employed to detect worn piston-rings is to place one’s ear close to the breather pipe of the en- gine while it is being turned over by some one else. If the pistons and rings are very loose, the air getting by the pistons can be heard distinctly when each piston is on its compression stroke. Judging Engine Vibration Q.—Sometimes I think the oil gage on my engine does not register accurately. Will you please tell me by what other methods I can determine if there is too much oil in the engine ?—H. K., St. Louis, Mo. A.—An overlubrication of the engine will result in rapid carbon deposits. These, in turn, will result in overheating and a loss of power on hills. Too much lubricating oil is indicated when the exhaust gas is bluish white in color. A light smoke of little density is not necessarily a sign of too much lubrica- tion. Prevent Frozen Radiators Q.—Is it considered a good practice to use kerosene in the radiator water to prevent freezing ?>—F. O., Newark, N. J. A.—Kerosene is not recommended as an anti-freezing compound principally because of its harmful action on the rubber hose connections. Alcohol or glycerine or any other patented anti- freezing mixtures can be bought at almost any garage and are preferable to kerosene. Gas-Engine Temperatures Q.—In the average automobile gasoline engine, what is the temperature and the pressure a square inch inside the cylinder at the time of the explosion?—A. B., Philadel- phia, Pa. A.—The temperature at the moment of explosion varies with the design of the engine, but is generally between 1200 and 1800 degrees F. The pressure also varies according to the engine de- sign. With an engine compression of 75 to 80 Ibs. a square inch, the pressure at the time of explosion would be be- tween 300 and 400 Ibs. a square inch. repa ser’ The took mob to | bon valv erat that don for the kne abo bile tha defi be ste! ma did wit the tha like sta car ant ine ‘ the the the on abi

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April, 1921 Save Repair Bills “THE excessive charges for small and simple repairs that are isually made by automobile service- tations, as well as automobile repair shops, have done more than anything else to. stimulate the average owner of an-automobile to learn the con- struction of his car and undertake to io the less difficult repairing himself, according to an enthusiast who has been able thus to reduce the expense of keeping an automobile. Especially in the suburban communities it is a common thing to see owners repairing their automobiles which formerly they were accustomed to take to the repair- shop. “The first year I had an automobile,” said a suburban automobile owner, “T had an idea that the only place where it could be properly repaired was at a service station. The first time I took my _ auto- mobile there was to have the car- bon removed and valves ground. ‘When I enum- erated the things that I wanted done, and asked for an estimate of the cost, which I knew was usually about $8 for a four-cylinder automo- bile at most garages, I was told that it was not possible to set any definite figure. In addition, it might be possible that some of the valve- stems were bent, and these would make for additional cost. “‘However, when I insisted that I did not want to have the repairs made without knowing more definitely what the job would cost, I was informed that the charges would be something like $9 or $10. With that under- standing the automobile was left for carbon removal and valve-grinding, and the resultant expense was $9.95, including a new gasket at 95 cents. “The next time I desired to have the carbon removed, I went back to the service station, but failed to take the precaution of getting an estimate on the work, thinking it would be about thesame. When the bill was pre- sented, it amounted to $18, and thelarg- est item in it was for labor at $1an hour. “This experience showed me the necessity for undertaking the work myself, and the next time that it be- came necessary to remove the carbon ind grind the valves I got a few point- ers from one of the skilled mechanics at the garage where I kept the car. [ was a little slow with the first under- By James G. Hilton Study your automobile and save money by doing minor repairs taking, but I was able to take the automobile entirely apart, then clean it, and assemble the parts again within six hours, and I was also able to use the old gasket, which was still in good condition after the second time the carbon was removed. “In all my experience in removing earbon, I have yet to find a valve- stem that needed replacement, and I have run my car nearly 10,000 miles. I figure that, even granting that the service station pays its mechanics $1 an hour, an $8 charge for the job is a fair one. “On another occasion I had taken my automobile to a service station to have a repair made so as to stop grease and oil leaking into the brake- drum. When I got the itemized bill, it included charges not alone for this specified repair, but charges for new felt wash- ers, readjustment of foot and emergency brakes, and other things I had not ordered. Ap- parently an_ in- experienced work- man had done the job, and before I drove the automo- bile home, a dis- tance of fifteen miles, the grease was leaking into the drum again, and I had to take the automobile back to the service station several times before the defect was remedied. The trouble was found to have been caused by putting too much lubricant into the differential housing. “Encouraged by success in making those first repairs, I finally got up the courage to explore other parts of the automobile, and I not only found that I could keep the different mechanisms in good running order, but I believe I take somewhat more care in doing these jobs than the average green mechanic who had done previous re- pair work on the same automobile. In addition, I have always found a great deal of pleasure in learning all about the construction of the auto- mobile, and the knowledge so acquired has stood me in good stead.” The owner estimated that the re- pairs on his car during the first year cost him from $75 to $100. During the present year his total repair bill has been under $1, and this included 15 cents for a foot-brake cam support which he replaced when the part was snapped by an obstacle bouncing up from the road-bed, and a terminal for the storage battery. 81 Protecting a Gear-Box Fork Plunger E recently had occasion to deter- mine the cause of a faulty gear box on one of the automobiles in our garage, and an examination revealed the fact that dirt and dust had entered at the point where the forks that hold the shifters in position, were | ‘ieaieica NG FORK placed. This | ee caused the PLUNGER locking plun- (~~~ — ' gers to bind, | with the result | that the shift- ! ing of change if ‘9 gears became a source of con- stant annoy- ance. The repair consisted of reboring and tapping the spring retain- er, and placing therein a closed cylin- drical cap, of such length as to enable the plunger to easily operate the desired amount. Incidentally, the cap served as a grease cup. -ADOLPH KLEIN, \ NC PLUNGER ~ SPRING SPRING RETAINER “CAP GREASE Lane The cylindrical cap protects the locking plunger from dirt and acts as “grease’’ cup w*-WHERE DIRT ENTERED Repairing a Worn-Out Hand Tire Pump HE writer recently had occasion to use his hand tire pump and found the threads stripped where they are threaded into the base. Not being able to find a repair part, he proceded to fix it up himself. In the accompanying illustration A shows the cylinder made of steel tub- ing, B the piston-rod assembly, C a sec- BRAZED HERE ) The tire pump with worn-out thread was fastened to its base with a machine screw tion of the cast-iron base, all of which are component parts of the pump. A piece (Ff) was turned up on a small lathe out of machine steel and brazed into the end of the cylinder. This piece had a °4-in. tapped hole in the center and a 3/16-in. air vent-hole at one side of the center. This air vent-hole is used to get the air down to the port that leads to the hose. After brazing into the tube, the cylinder was pulled down into the base by the screw E and the whole seated on the leather gasket D.

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How to Construct an Oil-Level Indicator By Adolph Klein "THE drawings herewith illustrate the details of an oil-level indicator that was built from odd scraps of material taken from the garage junk- pile. The gage was built by the owner of an old type of automobile, who was invariably annoyed by the fact that he could never tell how much oil was in the engine crankcase of his car. He ay & ROUND HEAD q = MACK SCREW i

SOLDER INDICATOR ROD i OD 5 DIAM

BRASS TUBING

§ ORL

lower crankcase and guides the lower portion of the rod. It is well to remem- ber that the cork float should at all times be thoroughly shellacked. The measurement scale on the gage body is determined in the following manner: The entire gage is assembled, and screwed into position by means of the two machine screws, after which 20 THOS DRILL yaa © Opi

From odds and ends found in almost every garage a thoroughly efficient oil-level gage and indicator like that shown here may be made finally determined to construct for himself some form of gage that would readily inform him of the amount of lubricating oil that his crankcase con- tained. This same type of gage could be employed in connection with the various forms of liquid-carrying tanks used around the garage. The body of the gage was made from a discarded starting-crank handle, made of brass, of the dimensions indi- cated in the diagram. The tube had a rectangular slot cut along the length of its axis, upon which a graduating seale was scratched. The manner in which this graduating scale was made is as follows: To the body was fastened a flange and the plunger guide. The flange, circular in shape, was made from an old thrust-ball bearing, and was soldered permanently to the tube. In addition, it wil] be noticed that this disk was provided with two 3/16-in. holes for permitting two machine screws to pass through it and into the crankease wall. The plunger guide was turned from a scrap piece of bar brass, and was soldered to the lower portion of the gage body. <A cap covers the top of the body and prevents the dirt and grit entering the inside of the gage. To further prevent this, a glass tube is inserted inside the brass tube. This glass tube is made of such diameter and length that it is held securely in position when the cap is screwed into position. The plunger- rod is threaded at the top for a knob and ‘at the bottom for a cork float. A hexagonal nut, placed on top of the float, and another, placed at the bottom, hold it at all times firmly. Another flange is screwed into the all the oil is drained from the lower erankease. In this position, the knob at the top of the plunger rod should come approximately 14 in. above the lower line of the slot in the gage body. In this position, a small horizontal line is scratched on the tube directly beside the knob. This line is marked O, indicating that in this position, there isn’t any oil in the crankcase. The case is then filled at intervals with quart amounts of oil and the po- sition of the knob is indicated with the proper figure, corresponding to the amount of oil that has been poured into it. Protecting Freshly Varnished Mudguards from Dust AINTING and _ varnishing the body of an automobile requires scrupulous cleanliness and great care to prevent the dust, which is nearly always found suspended in the air,

——— Z a, me / CO |r VIEW Sa VIEW STOP BLOCK FRAME IN

After the automobile has been paint- ed and varnished, protect it from dust while drying 82 Popular Science Monthly from settling on the freshly painted surfaces. When automobile bodies, the sides of which do not project, are varnished, the engine cover is usually removed to be varnished separately indoors. The mudguards, however, remain in place, and are exposed to the danger of being marred by dust dropping on the var- nish before it has had time to dry. An adjustable device to protect the mudguards from dust after they have been painted and varnished is shown in the accompanying illustration. The light wooden frame, similar in form to the frame of a door-screen, but much narrower, is fitted at one end with a pair of adjustable legs fastened by bolts to a block on the frame and kept at a certain angle by a stop block. The frame itself is covered with heavy paper. There should bea frame for each side of the car. Two legs only and both of them at the same end are required for each frame. The other end of the framework is supported by a stick or board laid across the engine. In garages where a number of automo- biles are housed, such frames will be extremely useful. When ihey are not needed they can be folded up and stowed away in some corner for future use.—_JAMES M. KANE. An Indicating Device for Storage Batteries TORAGE batteries are used at the present time on a majority of automobiles and trucks. Thousands of them are ruined through neglect to

Es ie p

LEAD ANTIMONY ROD AND WASHERS, TIPPED VENT ay 6 WITH CADMIUM AT_LOWER END WIRE TO VOLTMETER SWITCt

SECTION OF CELL

This indicating device shows whether there is enough electrolyte in your storage battery add distilled water to the battery at the right time. The indicating device shown in the accompanying illustration should be of interest to the automobile owner. The voltmeter and switch can be placed on the dashboard. The instru- ment will] tel] at a glance whether there is sufficient electrolyte in each cell and will also give the positive cadmium reading of the cells, showing their charging and discharging voltage on the dial.—F. S. BURROUGHS.

fix tes an do: BUL!

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April, 1921 | How to Make an Electric Contact Gage By Frank W. Harth HERE there are Jarge numbers of parts to be tested, the use of a feeler gage is tiresome and therefore apt to be somewhat subject to error. A fixed gage will wear very quickly unless tested every so often by a master gage and then adjusted and resealed. Fast and accurate testing can be done with the electrical gage shown in RETAINING 3 DRY CELLS Cc at TION a MBATTERY |NSULATION In this electrical contact gage the object to be tested is passed between two contacts representing the plus and minus limits the accompanying illustration. As this gage is adjustable it can be kept accurate at all times. The dimensions of the gage will be governed by the size and character of the work to be tested so that the design as shown in the illustration will be merely considered as suggestive. The base and arms of the gage are made of two pieces of tool steel, one piece, A, being L-shaped and the other, B, being straight. As the measure- ments are determined by electrical con- tact, the two arms are insulated from each other at the point C. The draw- ing shows, in detail, the method of in- sulating and binding the two arms together. The surface D to E must be ground and finished perfectly level. The two contact arms are also made of tool steel, the surfaces F and G being ground and finished perfectly straight. The surfaces D, E, F, and G must, of course, be hardened and lapped per- fectly parallel. The lugs H and J on the contact arms are provided as stops to prevent the arms from sliding out of their grooves. Two grooves are milled in the arm B and a plate is fitted to retain the contact arms in the grooves. The plate is firmly held in place with a machine screw. The grooves in the arm B must be cut true so that when the contact arms are fitted there will be a minimum of up and down or side play. Two holes are drilled and tapped as shown for the stops. These stops are fine thread machine bolts provided with lock-nuts. The contact arms are held against the stops by springs. These are light, just enough to cause the arm to return should they be lifted by an oversize piece. This will insure mini- The gage is fastened to mum wear. the base by means of two angle-pieces. To indicate electrical contact a flash bulb and battery are provided. The battery can be concealed in a base under the gage and the bulb fitted to the base at one side of the gage. The wiring of the gage is shown. The operation of the gage is simple. When a piece that is being tested fails to pass the contact arm F, the light wil) flash showing that the piece is oversize. Should the piece pass F without flashing the lamp, but makes contact with G, then we know that the piece is within its plus and minus limits. However, should the piece pass both contact arms, it is undersize. Enough battery voltage should be used so that it will take actual contact to light the bulb. Use a Tomato-Can for a Small Oven AN old tomato-can, placed upside down over the simmering burner of the gas-range, makes a good oven. A steel lid should be placed over the blaze and a small baking-dish placed on the steel cover. The tomato-can, with the lid completely removed, is then turned over the dish and the miniature oven is complete. Many times the housewife finds it Economize by using this tomato- can oven for small things requiring little heat necessary to heat the entire oven for a small amount of baking. This is a waste of gas. The small baking-oven may be used with a gasoline or coal-oil stove as well as with the gas-range. For small amounts of baking it has been found that this method is quicker, as well as cheaper.--CLEMENTINE PADDLEFORD. Umbrella-Rib Substitutes as a Drill-Bit HE load of shot contained in the magazine of my air-rifle became clogged a short time ago and I found it impossible to discharge or draw it. I tried drilling the lead out of the tube of the magazine, but I had no drill long enough. Another difficulty was that the lead chips would fill the space between the drill and the walls of the tube, which made it impossible to turn 83 the drill. While looking around to find some tool that I might use for drilling out the lead, I found an old umbrella rib, one end of which was broken off. To my delight, I found that the rib, when used as a drill-bit, worked very effectively. To improve its efficiency I filed teeth at one end and tried it again. It cut the lead shot easily and didn’t bind, as the borings found an outlet through the channel of the rib. The drill may BORINGS SLIL 2E THROUGH MBRELLA RIB In a case of emergency an umbrella rib may be used as a drill-rod if other drills are not long enough be used at either end of the magazine tube. Should it cause scratches in the tube, these may be smoothed out with oil and emery-powder or with a piece of emery-cloth wound around a stick or rod fitting loosely in the tube. This tool should be drawn back and forth through the tube with a plungerlike motion in order to obtain the final smoothing. —JAMES M. KANE. Constructing a Stand for a Micrometer ITH all his adjustable and fixed limit gages the inspector still finds his micrometer a handy device. And there are many cases in our shop where it would not pay to make up gages, and in some cases to set adjust- able gages, especially for small light work. With this need at hand, the writer built a simple, cheap, and effective stand for micrometers as shown. It consists of a hard maple piece (B) cut out to fit the micrometer (A) and split with a saw kerf to act as a clamp. The clamping is done with the wood screw. This hard wood piece is glued and driven snugly into an old platform When many screws or bolts of the same size have to be test- ed, it is convenient to hold the gage in a fixed position WANN) HAH) HA MbHTT TH EH ht MNAAHAATIIY MZ } | + dn thei seale weight (C), which serves as a base to keep the whole upright. It is a very easy matter to set a pair of ‘‘mikes’”’ in the clamp, and its handiness is be- yond question..-W. BURR BENNETT.

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To Make a Self-Adjusting Porch Chair By Frank AS a rule, the average adjustable armchair, the morris-chair, for instance, although comfortable, is at best too cumbersome and heavy to be moved very easily. The chair shown in the accompany- ing illustrations is very light in weight and simple in construction. It can be taken apart and packed compactly, making it ideal for transportation to the summer camp or bungalow. The chair is adjustable to any position, this being accomplished by the occupant’s moving his or her body backward or forward and by straightening or bend- ing the lower limbs at the knees. Reference to the illustrations will show how the chair is constructed in detail. The legs or side pieces are made of 1-in. strap iron 3/32 in. thick. The feet are made by twisting the iron in a quarter turn about 5 in. from the end and then bending it into a half circle as shown. The forward legs are a trifle longer than the rear legs. This is to provide a slight rearward tilt to the arm pieces. The two legs are then riveted as shown. The metal part of the arm piece is composed of 34 in. by 114 in. angle-iron to which the upper ends of the legs are riveted. The arm- rest itself is made of wood, shaped with a round on top and then fastened “kh D qa ; —\— ROLLERA WOOD PIECE 34x32 252" — " ly “ROLLER B > 4/ + Follow this diagram and you will find how simple it is to make a porch chair to the angle iron with flat head wood screws. The arm-rests may be of the plain wood or they may be padded and covered to suit the fancy of the maker. Those on the chair illustrated are covered with the same materia] as that used on the back and seat. The ma- terial in this case being canvas or awning-cloth. The sides are duplicates, with the exception that the leg positions are reversed. The two sides are bound together by braces made of °¢ in. by 1/16 in. strap iron, shaped and pinned together with rivets as shown. The back-rest, seat, and foot-rest are made W. Harth of two iron side pieces with cross braces of wood. The iron side pieces are made of *4 in. by 3/32 in. strap of the length shown and riveted as in- dicated. The rivets, which act as pivots, should be a trifle loose so that the moving parts will have free play. The side pieces composing the seat are bent at the rear end as shown. This can be done in two ways—the Can you imagine anything that would be more welcome on the porch in summer ? first by forging and the second by two quarter twists and a bend, as shown in the detail sketch. The distance from hole F to hole G must be exactly the same as the distance from the hole H to hole J. If these distances are unequal, the seat will not function properly and the action will be uneven and jerky. The wooden cross pieces or rollers should be of hard straight grained wood about 114 in. in diameter. These rollers are held in place by long 3/16-in. round woodhead screws. The holes in the ends of the rollers should be carefully centered and bored before the screws are put in so that the wood will not split. The canvas back, seat, and leg-rest is in one piece, securely sewed at rollers A and B, passing over roller C and around the flat piece D, and is also very securely sewed at E. This stitching must be strong, as it is called upon to support almost the entire weight of the person occupying the chair. If bolts are used instead of the rivets F, H, J, and K, the chair can be taken apart and compactly bundled for transportation. This chair will be found surprisingly light if weight. Mounting Double-Weight Photographic Prints ANY times the amateur photog- rapher wishes to mount his buff-colored photographs on cards, as it gives them a more artistic appearance than when they are left unmounted. Double-weight papers are usually made so thick that it is very difficult to make them adhere to the card without their becoming loose at the edges. Hence many amateur photographers 34 Popular Science Monthiy give up the mounting in disgust and content themselves with unmounted pictures. By using the following method, prints will stick perfectly to their card mounts and lay flat without a wrinkle. Wet the prints thoroughly and lay them face downward on a sheet of glass. Press the water out with a roller squeegee, and turn the plate of prints on edge to drain. Then paste the center of the print, working up to within 14 in. of the edges, putting on a reasonably thick amount of paste. Take liquid glue and put a thin coating of it on the margins of the print. Place the print on the card, and roll with the squeegee. After this is done, take a damp sponge and wipe all of the paste off and also any glue which may exude from the edges. After the print is dry, bend the card in the reverse direction to the curl and it will stay flat. Thick ordinary starch paste spreads easier than the glue, but the latter holds the edges of the print firmer. —W. S. STANDIFORD. A Broken Oyster-Knife Becomes a Chisel YSTER-KNIVES are made of finely tempered steel, yet they will occasionally break, if abused beyond the breaking-point. If your oyster-knife should break as the result of too strenuous use, do not throw it away. It is too valuable to be dis- carded and may be made a useful addi- tion to your set of tools. File or grind It is plain to be seen that an oyster- knife makes a practical chisel the tapered blade at right angles, and give it a good cutting edge, taking care not to destroy the temper of the blade. This gives you a chisel that will do excellent work in cutting light metal and even stone, provided it is not too hard and gritty.—JAMES M. KANE. To Lock the Neck-Yoke to the Tongue O prevent the neck-yoke from slip- ping off the tongue when different teams and harnesses are used, weld a ring twisted 90 degrees in the strap- iron loop at the end of the tongue. Puton saccx yore —. O the neck-yoke ” in the usual manner and link the lower loop to the ring with a clevis, thus holding it on. If welding facilities are not at hand, a twisted clevis can be used just as, conveniently.—J. ALEXANDER. How yoke and tongue are kept together stat the stiff inte Sim fast and fror The was the othe in t mags wire wet shra it a pair fan ousl draf othe exac as t] & req stak swil rest tion han grac usec pro] Weis mas was sma The inse san dep whi of t whi Spo The boa laps peri afte

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April, 1921 Causing the Electric Fan to Oscillate By Henry A. Germain HE accompanying sketches show the device which we applied to our stationary electric fan to get from it the effect of an oscillator. A frame of stiff iron wire was made by bending it into the form shown in the illustration. Simple hinges of strap’ brass were fastened to the guard of the fan at top and bottom of a vertical diameter and from these the frame was suspended. The back end of the lower hinge strap was bent down and drilled to receive the hooked end of a light spring, the other end of which engaged the loop L in the lower leg of the wire frame. A mass of lead, M, was cast around the wire, and over the frame was stretched a piece of unbleached muslin. Upon wetting it and allowing it to dry, it shrank tightly over the frame and on it an artistic member of the family painted an American flag. When the fan is running, the flag waves continu- ously from side to side, throwing the draft of air first one way and then the other. The proper weight to use and its exact location along the wire, as well as the proper amount of spring tension An electric fan is much"more satisfying if it is of the oscillating variety — required to keep the oscillator in un- stable equilibrium so that it would swing continuously and not come to rest in either an extreme or in mid posi- tion, had to be determined by trial, by hanging on convenient weights, and gradually tightening the elastic band used as a trial spring. When the proper conditions were reached, the weights were replaced by the single mass of lead of equal weight. The lead was cast around the wire by using.a small round cardboard box as a mold. The box was slotted axially, the wire inserted and the box buried in wet sand in which a small funnel-shaped depression was made, the bottom of which ended at a hole in the upper side of the box. Into this funnel the lead which had been melted in a large iron spoon over the gas-stove, was poured. The wet sand prevented the card- board from burning through or col- lapsing before the lead had set. Of course the cloth covering was not permanently stretched in place till after the lead was cast on. Besides the advantage which an | |e Wut + Wt Wa Webe He Lae bei et + oscillator possesses over a fixed fan in covering a wider angle, thus being of benefit to a whole room rather than merely to a narrow lane directly in front of itself, it has the added ad- vantage, which few appreciate, that an intermittent breeze is much more effective for cooling than is a steady This is due to the fact that the breeze. Showing the frame of wire and the meth- od of attachment to the stationary fan feeling of coolness which a breeze gives depends on the evaporation of mois- ture from the surface of the skin, the latent heat of evaporation of this mois- ture being supplied by the skin which consequently is cooled. Now, if a breeze blows steadily, the moisture is licked up as fast as formed, keeping the surface dry; whereas with the inter- mittent breeze the surface becomes moist during the intervals of stillness, with the result that when the breeze blows again, the cooling takes place much more rapidly and the effect is correspondingly more refreshing. Placed on a shelf in the corner of a summer porch the waving flag makes a very attractive decoration, thus being ornamental as well as useful. A Method of Punching Holes in Sheet Metal F it is necessary to cut a good many holes in sheet metal and time is a matter to be considered, the work can be very satisfactorily done with a punching outfit which is easily made. The dimensions will depend altogether upon the size of the sheets to be punched, but the idea is so simple 3 (poo oe With such an apparatus as this, holes can be quickly punched in sheet metal that it can readily be applied to prac- tice. Make a pair of guides as shown in the illustration. If there is much work to be done, it will pay to make them of tool-steel, hardened and tem- 85 pered, or of mild steel and have them casehardened. Near the ends drill for two bolts. Be very particular to use accurately finished—not rough—bolts, and have them fit closely in the holes so there will be no shifting of the guides. When this has been done, bolt the guides together and drill holes of the same sizes you want to punch. The position of the holes and the number and variety will depend, of course, upon the work to be done. The holes must be smooth and true and go clear through both guides. The punches are simply pieces of round tool-steel fitting closely, but not tightly, in the holes. The cutting ends are made square and true and hardened to a medium straw-color. To punch a hole it is necessary only to clamp the sheet metal between the guides, locat- ing the place to be punched under the proper hole, and send the punch’ through with a sharp, clean blow of the hammer. A little oil makes a better job. Making a Lock-Spring Out. of a Clock-Spring PRINGS of alarm-clocks are as arule not so highly tempered as to prevent them from being cut or filed. This quality renders them very useful for replacing flat lock-springs that sometimes break. Should the clock- spring be too gt---DISCARD THIS PORTION wide, it can be ag Ut THis PART cut with a pair of tinner’s shears, or it may be placed in a vise as shown in the accompanying illustration, al- lowing only so much to project above the jaws of the vise as you wish to discard. The part above the jaws may be cut off with a chisel and the rough edge filed smooth.—JAMES M. KANE. How a clock-spring was cut To Polish Woodwork on the Lathe ROFESSIONAL turners and ama- teurs doing lathe-work in wood often find it necessary to polish turned wooden objects, like candlesticks, table legs, etc., after the lathe-work on them is completed. A very simple and highly effective method of giving to such objects a high polish in a very short time is here described. Place the article to be polished be- tween the faceplate and the tailstock on your lathe and use alcoholic shellac varnish mixed with one half its volume of boiled Jinseed oil for polishing. Shake the mixture well before using it. Pour a small quantity of the mixture on a cloth and start the lathe, hoJd the saturated cloth against the revolving object, keeping up the friction until the polish is as bright as you desire.

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Finding New Uses for Old Things What use have you for some of the “junk” in the attic or cellar? Popular Science Monthly will pay ninety dollars for the best answers HERE is the old baby-carriage, the old stove, the old bureau, the trunk, and the leaky wash-boiler. The attic also contains old phonograph needles, safety-razor blades, carpets, curtains, chairs, tables, picture-frames, hat- boxes, etc. Have you been able to save money and add a convenience to your home by pressing some of these things into service again? If you have, you probably had to get the household tool-kit out to help you. Sit right down now and tell Popular Science Monthly what changes you made and how you made them. It makes no difference what you changed, as long as it wasold. You may win one of the prizes. The Popular Science Monthly offers three prizes for the best answers—a first prize of $50, a second of $25.00, and a third of $15.00. These will be awarded in accordance with the rules outlined below. Rules Governing the Contest (1) Contestants are not limited to the number of ideas, but only one method can possibly win the first prize, only one the second, and only one the third. The con- test is open to everybody. (2) The use of the old piece of junk must be shown clearly, either in a photograph or in a drawing. If a drawing is sent in, it need not be made by a skilled draftsman. It is sufficient that it should be intelligible. While pen- cil sketches will be considered, contestants are requested to make their drawings in ink on heavy white paper. The views should be sufficient in number to set forth the writer’s idea very clearly. The con- testant’s name and address should appear on each sheet of drawings. (3) The drawings or _ photo- graphs must be accompanied by a description, preferably type- written, in which the method is clearly given. It must be written on one side of the paper only, and it should not be more than 500 words in length. The name and address of the contestant should appear in the upper left-hand corner of the first sheet of the written description. (4) The drawings and descrip- tion entered by contestants must be received by the Popular Science Monthly not later than 5 p. m., on June 15, 1921. (5) The judges of the contest will be the editors of the Popular Science Monthly. (6) The first prize of $50 will be awarded to the contestant who, in the opinion of the judges, has suggested the best use for an old piece of junk. The second prize of $25 will be paid to the contestant who sub- mits an idea next in merit. The third prize of $15 will be paid to the contestant who sub- mits an idea third in merit. (7) The winners of the contest will be announced in the earliest possible issue of the Popular Science Monthly. A description of the ideas that win the three prizes offered will duly appear in the pages of the Popular Science Monthly, together with the names of the winners. ' (8) The editors of the Popular Science Monthly shall have the right to publish meritorious manu- scripts that do not win a prize. The regular space rates will be paid to the contestants who sub- mit the manuscripts thus selected. (9) When a contestant submits more than one idea, the descrip- tion and drawing by which each is set forth must be sent as a sep- arate unit. (10) Manuscripts or drawings will be returned to contestants if stamps are enclosed. (11) Send drawings and specifi- cations to the Editor of the New Uses for Old Things Contest, Pop- ular Science Monthly, 225 West 39th Street, New York City. 86 Popular Science Monthly Keeping Fish Fresh for Several Days ITHOUT ice I have kept fish fresh and full flavored for three or four days in the heat of August, and in cooler months for weeks at a time, in the box shown in the picture. Most people make the mistake of putting freshly caught fish in water until they want to eat them. The water soaks out the flavor of the fish and also softens the food. Also fish will hardly keep twenty-four hours in water before they show taint and spoil. The box shown in the picture is 24 in. long, 18 in. wide, by 20 in. deep. It was sunk to half its depth in the brook . es i * a + hens Before you start on your-next fishing- trip, make yourself a box like this that flows from a spring. A wire tray is held on a shelf made with !>-in. sticks placed 14 in. apart. This shelf is 3 in. from the top of the box. As soon as fish are caught, I dress them and wipe them dry with a clean cloth, then place them on a layer of ferns in the tray of my box. A layer of ferns over the fish also helps. Holes bored in the cover and sides, then covered with wire netting to keep out flies, allow free circulation of cool air. For convenience, the cover of the box was hinged in place. The water flowing through the box by means of several 1-in. holes bored in the bottom and low down on the sides, always keeps the air cold and the fish will keep for days. Roofing-paper keeps the sun away.—F. E. BRIMMER. Steel Wool Used as a Filler When Soldering HERE are a thousand and one different and distinct uses for steel wool, from finishing bowling-alleys to cleaning pans. The latest, however, is in connection with soldering. Many times when a hole is too large to fill with solder, or the material for a plug | is not handy, a wad of fine steel wool | will furnish | solution. just exactly the right Especially is this true in the mending of lead pipe, where a queer- shaped crack makes plugging almost impossible. Just fill the opening with steel wool, then run in the solder, and a perfect seal will result, for the solder | changes the spongy plug into a solid.

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April, 1921 \ Hang ERWOOD i qh, UN coos > Actual photo of one ef our re- built Underwood Typewriters. Puts It on Your Desk DIRECT FROM FACTORY TO YOU S, only $3.00 brings you this genuine Typorium Rebuilt Standard Visible Writing Under- wood direct from our factory, arid then only small monthly payments while you are using it makes it yours; or, if convenient, pay cash. Either way, there is a big, very much worth while saving, too. Genuine new Underwood parts wherever the wear comes—genuine standard four row, single shift key board—thoroughly tested—guaranteed for 5 years. suximensmeinse Underwood Standard Typewriter you from our big modern ae sian ‘ : patna: Jactory (shown below)-—the Rebuilt like new. Every typewriter is factory rebuilt by typewriter experts. New enamel—new nickeling—new largest typewriter rebuilding _lettering—new_platen—new key rings—new: parts wherever needed—making it impossibie for you to tell it from plant in the world. a brand new Underwood. An up-to-date machine with two color ribbon, back spacer, stencil device, auto- matic ribbon reverse, tabulator, ctc. In addition, we furnish FREE, waterproof cover and a special Touch Type- writer Instruction Book. You can learn to operate the Underwood in one day. Easy Payments 10 Days’ Free Trial You don’t even have to scrimp and Remember, you don’t even have to save to pay cash. Instead, you pay buy the machine until you get it only a little each month in amounts and have used it on 10 days’ free so conveniently small that you will trial so that you can see for your- hardly notice them, while all the self how new it is and how well it time you are paying, you will be en- writes. You must be satisfied or joying the use of and the profits from else the entire transaction will not the machine. cost you a single penny. Bargain Offer Coupon! Now is the time whenevery dollar saved counts. Let ussave you FREE TRIAL COUPON many rl Don’t delay. Get ee wonderfuleasy payment bar- jm gain offer now,so you can send for and be sureof getting your i i Underwood at a big saving — on our easy terms or for cash. @ Typewriter Emporium ~ 2144 Shipman Building Act Now—Send Coupon Today! a Montrose and Ravenswood Aves., Chicago, Ill. @ Send by return mail Bargain Offer No. 2144 ofaStandard Visible Writing “ ~ Underwood. This is not an order and does not obligate me to buy. = co [Typewriter Emporium : MINN 4.3 w salbe- cue vedeeaccountae eames coeds voumassemseasenmaTdeanl Rebuilders of Underwood Typewriters Since 1892 ™ 2144 Shipman Building gg ee wibiaiiiaiaaa a aia * Montrose and Ravenswood Aves., Chicago, III. Post eee eee eee eee eee eT | CORREO OREO EE ES DEB O ee ee ee)

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Run Your Own Machine Shop Get the Repair Business in Your Town

You can easily rig up a dandy little power machine shop in your garage or a corner of the base- ment. A small Jumbo Gasoline or Kerosene Engine is the basis of a fine outfit for making auto repairs, mending and keeping all kinds of tools in A-1 condition. Save money by fixing up your own things as soon as needed. Be independent of slow, expen- Sive repairmen. Make money re- pairing for others. Build up a profitable, pleasant, spare-time business. The reliable power supplied by Jumbo Engines is more than half of mak’ag satis- factory repairs. a) TBO ZNGINES 3 to 12 h. p. More than 115,000 in daily use prove the popularity of these sturdy power plants. The Jumbo 1°%¢ h. p. gasoline engine is one of the neatest bits of machinery you ever saw—the exact replica of the more expensive larger sizes, every part carefully made and thorr ughly tested. These Jumbo Strong Points will show why Jumbo owners always have reliable economical power. Jumbo Strong Points Perfect Mixer—A specially designed mixer gives a perfect, uniform fuel supply with either kerosene or gascline.

Easy Starting—Pos- itive fuel supply and perfect ignition make quick starting easy and sure.

Positive Governor— Positive governor gives even speed un- der allloads. More magneto givesa hot, power when needed fat spark in all kinds andthenONLY— of weather. saves fuel,

Oscillating Magneto Webster oscillating

Send in your name and address and we will mail you a blueprint suggestion for laying out a shop, together with folder on Jumbo Engines and the name of nearest dealer. Write today.

NELSON BROTHERS COMPANY 1502 Owens Street

Saginaw, Michigan

Imitation Movies Without a Motion-Picture Camera Fine the amateur photographer has tried out all the usual camera tricks and novelties, here is a little novelty that may interest him. It consists of making imitation motion- pictures. The principle of this is very simple and easy to understand. Several photographs are mounted in book form

Turn the leaves of the book rapidly with your thumb and you will get the effect of moving-pictures and the pages rapidly spun by the thumb. If the pictures show the various phases of a motion, the effect will be that the subject seems to move. Since the number of photographs necessary is comparatively great, small sized pictures would be less expensive, in fact, the 1°¢ by 2% picture is fully large enough to give good results. The number of pictures may be any num- ber from 5 or 6 up to as many as de- sired. The pictures should be care-

Each picture shows a little progress in the motion of the person posing, in this case a girl walking fully made, as it is necessary for the subject to stop for each picture. Each picture should show an advancement in motion. As an illustration of the principle, see the photographs of a small girl | walking. The prints should be bound in book form, being pasted on paper as shown in the drawing. The book should be a

Three more poses of the same girl, rep- resenting the continuation of movement little larger than the print so as to per- mit of the full picture’s being seen. If the pictures are now rapidly thumbed, they produce the impression of motion of the subiect.—PuiLie A. WALL.

T° ‘ele

Popular Science Monthly —— —

$200 Saved By This Home Lover One housewife had selected $550 worth of Furnishings locally before learning of this new Larkin plan. The same selection at our low Factory-to-Family prices cost her only $350. Wasn't this saving of $200 worth- while? May we send all interesting facts? 1000 Furnishings at 20c a Day Small as well as large Furnishings’ needs are easily and quickly filled under this de- lightful plan. Payments as low as 20c a day. Completely furnish an entire home or parts of several rooms this convenient way, Get this Big 128-Page Book FREE Here is a complete guide for beautifying your home. You'll spend many profitable hours Mi] looking over this Book of Bet- fai ter Homes. Write for it now. | Find out how easily and eco- Hii nomically your home can be brightened.

t Er >

This handsome, most modern lamp will make any~*home brighter and more cheerful. No | glare, no flicker—just a flood of eye-restfullight— gepmummpms | Candle Power. // Burns 97% air and only 3% gasoline—gallon lasting 60 rs. No wicks to trim, no £ smoke, no odor; guaranteed 5 ij years. Choice of Silk, Dec- ii | orated or PlainShade, FREE LAMP to one person in each locality to whom customers can be referred. Write today for limited offer and free trial plan. THE RADIOLITE MFG. CO. 4 Dept.. 37F Milwaukee, Wis. Tires Cheap! “reso Biggest Tire Bargains Ever Offered 6000 Mile Guarantee Try Radiolite in Your Own Home

Size Tires Tubes 30x3 $13.50 $2.25 30x3% 15.50 2.50 32x3% 17.00 2.65 3ixt 18.12 2.75 32x4 19.96 2.85 | 33x4 20.70 2.95 34x4 21.04 3.10 34.4'5 26.30 4.50 35x4 54 27.26 4.75 36:4% 27.60 5.00 35x5 31.30 5.25 375 32.70 5.50 ORDER NOW. Discount of 5% when full amount accompanies order.

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Independent conomic al Transportation Catalog sent on request ~ Cleveland LIGHTWEIGHT MOTORCYCLE THE CLEVELAND MOTORCYCLE CO. CLEVELAND, USA THE MODEL T FORD CAR Its Construction, Operation and Repair, Including the Fordson Farm Tractor, F. A. Lighting and Starting System, Ford Motor Truck. Price $2.00 Postpaid. POPULAR SCIENCE MONTHLY, 225 W. 39th St., New York —

{ pri Car serve olor {2-ir and - a Tij smot and two clas] the the to we ing dif Cas fla lin wi of wi ca bli Se di dr

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tpril, 1921 Carry Water-Color Tubes in a Block of Wood WORKER in water-colors found that a case made from a 2 by 4 served well for carrying his tubes of ‘olors from one place to another. A {2-in. length of hard wood 2 in. thick and 4 in. wide was cut at an angle with a rip-saw. The sawed surfaces were smoothed with a plane and sandpaper, and the two parts fastened together by two hinges on one side and a small clasp on the other. Holes were bored into the body of the case of a size slightly larger than 4 “L, ‘aig ‘s ARG vA Ce wl . “ OF With saw and auger you may easily make a carrying box for your water- color tubes from a piece of wood the size of the tubes. Corresponding to these holes, somewhat larger holes were bored in the cover, and the open- ings reamed out to prevent any difficulty in opening or closing the case. The holes were lined with cotton flannel, glue being used to hold the lining in place, and the holes labeled with stickers, indicating the contents of each compartment. A wire handle, fastened to the top with two brass staples, completed the carrying-case, which was then stained a suitable color.—DALE VAN HORN. Has Your Work-Bench a Drill-Stand Like This? ERE is a simple idea and a great time-saver. Place an ordinary block of wood on the bench and drill a series of various sized holes to suit the different sized drills, marking the size under each hole. At the back of the block place a board on which paste a regular tap- =. size table. Every work-bench Place your should be equipped drills in the with a drill-stand. block. They re is one easily must go in their proper place to fit, and whenever you desire to drill a hole for any size tap within the range of the drills in the board, all your information is right at hand.—J. H. MOORE. THE CENTER OF 7 iN SAFET Y@IRAZOR | Simple Effective Safe “Just like wiping your face with a towel” More than 2,000,000 reg- ular users will say so Ws Crdors ENDERS SALES COMPANY 17 Battery Place, New York ENDERS SELLS FOR $1.00 with six blades of the best quality Swedish-base steel, hand-stropped and hand-tested. Packed in black Keratol box, velvet lined. Extra blades, package of 5—35 cents. FOR SALE BY BEST DEALERS EVERYWHERE Ra SHAVING INTEREST

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Mechanical Engineering Learn at Home! Employers everywhere are looking for men with mechani- cal ability. Splendid salariesand rapid advancement are offered. There is an easy, delightful way in which you can learn right at home in spare time. For 30 years the International Cor- respondence Schools have been giving men and women just the training they need for success in mechanical engineering and more than 200 other subjects. Hundreds of thousands have stepped into good positions through I. C.S. help, but never were opportunities so great as now. Let the I. C. S. help you. Choose the work you like best in the coupon below, then mark and mail it today. This doesn’t obligate you in the least and it will bring you information that will start you on a successful career. This is your chance. Don’t let it slip by. Mark and mail this coupon now. — eee eee eee es TEAR OUT HERE oe 3 ee oe INTERNATIONAL CORRESPONDENCE SCHOOLS BOX 7620-B SCRANTON, PA. Explain, without obligating me, how I can qualify for the position, or in the subject, before which I mark X. ELEOTRIOAL ENGINEER SALESMANSHIP Electric Lighting and Kys. ADVERTISING Electric Wiring Window Trimmer Telegraph Engineer Show Card and Sign Ptg. Telephone Work Railroad Positions MEOHANIOAL ENGINEER ILLUSTRATING Mechanical Draftaman Cartooning Machine Shop Practice BUSINESS MANAGEMENT say — Operating Private Secretary CIVIL ENGINEER sone Speeeeepondont Surveying and Mapping MINE FOREMAN or ENG'R a eo STATIONARY ENGINEER et Sees MANAGER Marine Engineer Railway Accountant Ship Draftsman Commercial Law ARCHITECT GOOD ENGLISH Contractor and Ballder Common School Subjects Architectural Drafteman CIVIL SERVICE Concrete Builder Structural Engineer S— PLUMBING AND HEATING = Mathematics Sheet Metal Worker f Textile Overseer or Supt. Navigation Spanish ONEMIST AGRICULTURE Teacher Pharmacy Poultry Raising Banking Name Present Business I-1-21 Occupation Address Street and No. . sali City State Canadians may send this coupon to International Correspondence Schools Canadian, Ltd., Montreal, Canada | FIG! A c —) FiG2 |o © FIG 3 TrIUMB NUTS FIG 24 pear FIG | A FIG.1.— Fig. 3 | my own scheme and with a sharp ' two 3%-in. flat head 6/32-in. machine Simple and Quickly Made Is This Section Liner AVING considerable shading and section lining to do, I desired to borrow a section ruler, but was unable to obtain one. Consequently I devised knife, some heavy cardboard, glue, TUT EHR [ i TT U EET Lt lI Hii] | will go. | slide the triangle as far as it will go and ood NT MET] Here the section liner is shown in posi- tion for drawing lines at an angle of 45° | screws, two battery terminal thumb | nuts, and two 6/32-in. washers, I made | the following section liner. Cut from the cardboard two pieces like Fig. 1 and one piece each like Fig. 2 and Fig. 3. The latter two are alike with the exception of the slot and drill holes. To the bottom of Fig. 2 glue one of the pieces like Fig. 1 and to the top of Fig. 3 glue the other. Through the holes in Fig. 3 screw the machine screws protruding through the slot in Fig. 2, and the assembly should be as shown in the cross-section. This a Popular Science Monthly Earn Up to $250 per Month Enter fascinating, new profession of Railway Traffic Inspection. Travel—all expenses paid. Some- thing new every day. Leads to splendid opportunities through contact with Big People. POSITION GUARANTEED at end of 3 months’ study. Any average man can qualify— lift himself out of the rut. Start at $110.00 per month; advancement and future assured after experience. Decide NOW to investigate. No obligation. Send for FREE Booklet D-225, Standard Business Training . Institute BUFFALO, N. Y. STA Why continue to MMER Send for (free) AM 200-page book. It tellg how Stamme a ing and Stuttering can be quickly cured by the most vanced Scientific Method in the wor'd. THE LEW s we HOOT, $6 Adelaide, Detroit, Mich. spare-time home & EVERY BICYCLE A MOTOR CYCLE wile using a STEFFEY ATTACHMENT. Easily attached, double-bar or truss frame. § ECONOMICAL — PRACTICAL —SUCCESSFUL. Send stam; eY Y for circulars. STEFFEY MANUFACTURING CO. Dept. S, 5025 Brown Street, Philadelphia, Pa Fits diamond N The parts of the device are here shown in detail, also a cross-section of the’ assembled liner will give a 5- to 7-in. spread and may be used with a 5- or 6-in. 45 degree angle or a 5-, 6-, 10-, or 12-in. 60-30 degree triangle. The method of using the section liner is shown in the first illustration, and needs little explanation. Draw a line along the triangle and then, hold- ing the triangle stationary, slide the cardboard instrument, previously set by tightening the set screws on the instrument, to the right as far as it Now hold the cardboard and again draw the line. This procedure is repeated until all the lines that you require are com- pleted.._THERON P. FOOTE. 90 BOUND VOLUMES OF POPULAR SCIENCE MONTHLY Each volume contains over 200¢ pictures, over 1500 new articles, making a handsome big book of 960 pages. Volumes available: v ol. 88, Jan.-June, 1916; Vol. 91, July- Dec., 1917; Vol.g2, Jan.-June, 1918; Vol. 93, July-Dec., 1918; Vol. 94, Jan.-June, 1919. Price, per volume, postpaid, $2.50. Book Department, POPULAR SCIENCE MONTHLY 225 West 39th Street, New York Books for Mechanics Sheet Metal Work—A manual of practica self-instruction in the art of pattern drafting and construction work in light and heavy gauge metal, including skylights and roofing cornice work, etc. Cloth, 288 pages, 37¢ illustrations. Price, $2.60, Postpaid. Machine Shop Work—A comeeenenst guide to the most approved methods in moder shop practice, the construction and use of in proved tools and machines, hand tools, th lathe and lathe tools, the methods of scre\ cutting, taper and eccentric turning, et leather, 360 pages, 401 illustrations. Pric: $2.60, Postpaid. POPULAR SCIENCE MONTHLY 22S West 39th Street, New Yor! fron mak nipE the mee left- they han pin» he A pi show split drille blade to m of he for tight Im y F . to benzi the t the p that may readi papel Ws can a this vy it tha of op ploye the d Th paper witho the tr jected made. little | Tress n squart benzir HAUS.

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ica} ting ivy Ang, 370 sive deri fim the cre\ et rice iLY York April, 1921 A Bucksaw Frame Made of Piping RIGID bucksaw frame, one that will never warp, break, or split, in be made from short lengths of com- ion gas-pipe at little cost. Take the measurements of the frame from an old wooden bucksaw. First, make the top bar and two short side nipples of 34-in. pipe. The halves of the top bar are threaded at the ends, meeting in the center with right- and left-hand threads, respectively. Then they are connected by a right- and left- hand threaded coupling fitted with a pin toturnit. The side pieces are of he same sized pipe and are shaped as A bucksaw frame made of pieces of gas pipe will never warp, break, or split shown. The two flattened ends are split to receive the saw and each is drilled to take the bolt holding the saw- blade. Bend thelong piece outward to make a handle. The middle bar is of heavier piping and acts as a brace for the frame when the blade is tightened.—_HORTON HALLETT. Improvise Tracing-Paper in an Emergency F the paper on which the tracing is to be made is soaked with a little benzine, using a cotton pad, allowing | the benzine to soak into the pores of | the paper, it will become so transparent that the most delicate lines and tints may be readily seen through it, more readily than through the finest tracing- paper. Water tints, India ink, and pencil can all be used on paper prepared in this way; pencil takes more readily on it than on any other paper. Any kind of opaque drawing-paper may be em- ployed, and should be stretched over the drawing in the usual manner. The benzine evaporates rapidly; the paper assumes its original opacity without leaving the slightest trace of the treatment to which it has been sub- jected. When large tracings are to be made, the benzine should be applied a little at a time, according to the prog- ress made while working. Only a few Square inches should be treated with benzine at one time.—HERMAN NEU- HAUS. CORBIN DUPLEX COASTER BRAKE You can have that Corbin Bra you want! All you have do is to tell your dealer t equip that new bicycle with the Corbin, and insist on his doing it! The Corbin has for twenty years steadily grown in popular favor and demand among bicycle riders who know brake values It has that husky build which makes it safe, sure to respond when emergency calls for quick, positive braking elust a slight pressure slows the bicycle gradually — slightly harder pressure brings a complete standstill— smooth, jarless, joltless, without the least harmful effect on your bicycle Ask for the Corbin. It lasts and i co perfectly as long as the wheel itself han together. Made and backed by Corbin your greatest assurance of long- sie All trouble-free service, highest quality mate- rials and workmanship Send us your address and we will mail you a free copy of Fred St. Onge’s booklet, ‘‘The Art of Bicycle Riding.”’ Corbin Screw Corporation American Hardware Corporation, Successor, 202 High Street, New Britain, Conn. Branches: New York, Chicago, Philadelphia lied I Library e if “Law Guide’’ free "Evid STUDY aT HOME Become a lawyer. Legally trained men win high positions and big success in business and public life. Greater opportu- nities now than ever before. Be bBb Es 10, aleader, Law- to' $10,000 Annually We guide you fm, B88 step. You can train at home luring spare time, We prepare you for bar examina tion in any any gtate Money refunded according to our Guarantee Bond if dissatisfied. Sonterred. of Jegree © mesa "en- oR, cost, easy terms. Four: teen volume ‘ou enroll now. Get ot valuable 120 page vidence’’ books free. Send for them—now. LaSalle Extension University, Dept. 483-L Chicago BUILT FOR 8000 MILES SERVICE and guaranteed against defects for 5000 miles. Patched or Retread new materials, which we are confident will give mileage equivalent to a cord tire. Standard non-skid, geared-to-the-road tread, of new live rubber same as drawing. New Tube Free With Every Tire Ordered—Good Tires backed by real guarantees cannot be sold any cheaper. SBEB os 0 $f 30 90x3 . «0 334 o « 80 . 32x3% 88. only 9.70 | State SS. or Clincher, W deposit. Tire shipped balance C.O.D., with section left unwrapped examination. If not satisfactory, deposit will be returned in full =—= FIELD TIRE & RUBBER CO., Dept. 191, Not a Sewed, ° A Brand Ride a Bicycle standard Brake rake | r Optional equipment on the yrbin The C bicy¢ les at it be equipped on following makes of Insist t! vours Dayton Snell National Yale World Excelsior Admiral Henderson Crown America Adlake Iver Johnson Emblem Pierce Pope Cleveland Indian and others ———— —. National College @ iatalogue oa of Chiropractic (RESIDENTIAL) 16 N. Ashland Blvd. Chicago Unsurpassed facilities for a com- plete Scientific Chiropractic edu- cation. Distinguished Faculty. Modern and extensive laboratory equipment. Large clinic. Gymnasium dormitory and etudents’ aid dept. Chicago's op portunity for self help unlimited. Enter quarterly. 3-yearterm. 14th Year: - ~ Tire—but a sturdy fabric casing rebuilt of 31x4 $10.95 32x4% 7. 55 36x4% $14.50 8.00 32x4 11. + 33x4% 13.10 35x5. 15.50 33x4 11.7 oo +2. 18 37x5 . 15.60 34x4 11. 95 35x4 00 SEND YOUR ONDE R TODAY with $2.0 28th & Wabash Av., Chic

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foe diitaaiice Nor Blow Out Yet they ride as easily asa pneumatic. Absolutely cannot injure the car. And wear until there is nothing left but shreds. The fact is. nothing can happen to Dayton Airless fires but w-e-a-r. This has been demonstrated on more than 100,000 cars, in all parts of the country, on all kinds of roade:, under all sorts’of conditions. They have also proved themselves the most economical tires, costing less per mile of service—and actually nothing for repairs Write for Booklet and Prices If you, too, want to free yourself from tire trouble and save money doing it, send for free booklet . We urge any business man who wants to build up a profit- able tire business to mail the oupon for our unusual money making proposition The Dayton Airless Tire Co. Dept. 255 Dayton, Ohio bee Dayton Aitase Tire o., Dept. pment oh. Please send me, without obli- gation, booklet, prices and more _information on Dayton Airless ires, as follow ‘Dayton Airless baesb-otes + HOME 9g em a wus é . Passenger Cars . Light Delivery Cars Seee sea Dealer's Proposition PNREED. cc cccvrcccccveccesccecewevececece | TTR TTT Tr OPEL LEE LEE Finger Print Detectives Wanted EN are wanted by the government, police M departments, corporations, banks, insti tutions and individuals—these men must be trained Finger Print Men—men who have made this work a profession. Big Salaries You can master this fascinating, big money- making profession by studying in your spare time at home. Common school education is all you need. A brilliant career is before you. Free Finger Print Book Tells you all about finger prints portunities in this profession, and everything you want to know about it. Send now for book and our special offer of a Secret Service Course —free. -the big op- University of Applied Science Desk 9204, 1920 Sunnyside Avenue. Chicago New Big No. 14-200 pp. Wireless and 100 pp. Electrical Catalog Wireless catalog mailed for 12c and electrical catalog for 6c. You may deduct this amount on first $1.00 purchase. Catalog not sent other- wise. Any wireless amateur will tell youitisthe one catalog to have. CATALOG NOG The Wiliam B. Duck Co. ANYTHING E_EcTPUCAL As an encyclopedia of information it is invaluable. The largest and most elaborate radio catalog pub- lished. Values that cannot be duplicated elsewhere. THE WILLIAM B. DUCK COMPANY 212-214 Superior St. TOLEDO, OHIO Thrust-Bearing to Support Spool of Fine Wire N winding electrical appliances with fine insu'ated copper wire of No. 34 gage or smaller, the wire is ex- tremely liable to break while being reeled off its spool, especially if wound at all tightly upon it, as the spool has to be rotated by the pull of the wire itself beingunwound from it. To overcome this difficulty an ordinary ball _ thrust- bearing is placed under the spool. In the sketch the BALL THRUST viSE spool is shown By placing a ball held = upright thrust-bearing in a vise, under your spool the wire will not revolving on break. an iron bar or piece of shaft- ing. If there is a large center hole, a couple of wood collars may be used to center up the spool. The use of this method allows the wire to be unwound without an undue strain being put upon it as the spool rotates with little friction when supported by the thrust-bearing. How to Loosen Tight Parts of Fountain-Pens OUNTAIN-PEN users frequently experience difficulty in removing the threaded or unthreaded cap when it works itself tight on the pen. The or- namental knurling is then found inade- quate, and various ‘‘tools’’ are usually resorted to, which often have the effect of wedging the cap on still tighter and causing it to crack. The foregoing applies even more to the threaded FOREF INGER ———| TIGHTLY WEDGED t— ppasep AT THIS POINT With a rubber eraser or a heavy rubber band the resisting cap of your fountain- pen can be easily removed ends of the barrel that must be re- moved to fill or clean. The illustration shows a _ simple method of readily loosening the cap. A soft rubber eraser of the type shown is held tightly around the part to be loosened, with the thumb and forefinger. This soft rubber eraser will then be found to grip the hard rubber surface perfectly, and to turn the part is then easy. A wide rubber band doubled over as shown will serve almost as well in its stead.—C. NYE. 92 Popular Scvence Mont).\y ——e — GET A HOBBY MAKE MODELS Start a Home Workshop ‘‘Model Making,” by R. F. Yates, de- scribes the construction of model gas-engines steam-engines, locomotives, boats, dynamos, turbines, railroads, guns, etc Thirty chap- ters are devoted to models of various naturé } It will help you to become a better m« chanic. It will help you to do hard solderin; soft soldering, lathe work, tempering, drilling, pattern-making, etc. Thisisa book every amateur or profession: | mechanic and model maker sho uld have. “Model Making’ describes real engi- neering models, not toys. 400 Pages, 300 Illustrations. Practical, complete, easily understood. Price, Post- paid, $3.00. Popular Science Monthly 225 West 39th Street, New York LEY'S. Meigen inl ‘oF —J TWENTIETH CENTURY Book of Recipes, Formulas and Processes This book of 800 pages is the most complete Book of Recipes ever published, giving thousands of recipes for the manu- facture of valuable articles for every-day use. Hints, Helps, Practical Ideas and Secret Processes covering every branch of the useful arts are given. 10,000 Practical Formulas—The Best Way to Make Everything A book to which you may turn with confi- dence that you will find what you are looking for. A mine of information, up-to-date in every respect. Contains an immense number of formulas that every one ought to have that are not found in any other work. Price $4.00 Popular Science Monthly 225 West 39th Street, New York a pru Hov T; farm encol them made Th ing f saplil hand: struc plana main at the have trestl If 1 trestl boar¢ borec ing t! as sh two | drive for t judgi legs t inche for ; heigh Of sary roun if avi horse pape: plece broo! trest! one — fittec and | early build Virile TI of tl doub for t the ; Wate This room . It ea §¢6h UC. |

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ote ee April, 1921 How to Make a Three-Legged Horse or Trestle HERE is always plenty of use for wooden horses, or trestles, on the farm, but because of the difficulties encountered in the construction of them, boxes, barrels, etc., are usually made to take their place. The trestle shown in the accompany- ing figure may be easily made from saplings, with no other tools than a hand-ax and a large auger. The con- struction is so simple that little ex- planation would seem to be needed, the main difficulty being to bore the holes at the proper angle so that the legs may have the correct spread to hold the trestle steady. If the log that forms the top of the trestle is temporarily fastened to a board, the holes for the end legs may be bored in line with each other by keep- ing the auger parallel with the board, as shown in Fig. 2. The legs for these two holes should next be fitted and driven into place, after which the hole for the center leg may be bored by judging the angle of the auger with the

Three-legged horses like that shown here are very useful, used in pairs legs that are already in place. Sixteen inches is about the right spread of legs for a trestle two feet high, other heights in proportion. Of course it isn’t absolutely neces- sary that this trestle be formed of round sticks; square ones may be used if available. A pair of light and handy horses, suitable for such work as paper-hanging, may be made from two pieces of 2 in. by 4 in. and six pieces of broom, or hoe handle. Three-legged trestles should be used in pairs; if only one trestle is required, it should be fitted with four legs. Build an Improved Starting- Box for Spring Plants N improved starting-box, in which tomato, cabbage, lettuce, radish and many other seeds may be started early in the spring, takes little time to build and will grow bigger and more virile plantlings. The box shown in the illustration is of the improved type. Notice the double inclined bottom, which allows for the free circulation of air through the soil and takes care of the drain- water when the seedlings are watered. This box may be placed in the best room in the house because it will not

“Our first Real vacation’ ‘Dear -Bud:— “Margie and I just back from our first real vaca- tion—a week in the hills with the Harley-David- son. It’s the life, Bud! “Remember Eagle’s Nest? We pitched camp there, then tried out all the trails for miles around. You can’t stall the litttle old Harley-Davidson- and she’s still giving her fifty miles for a dollar, gas, tires and all. “It seemed good to have a real cook along. None of your bum flapjacks! Margie says we’ve got to count her in on all our trips after this. “So long, Bill.” Start planning your vacation now. The first move 1s to ask your Harley-Davidson dealer for a demonstration. Or write us for literature HARLEY-DAVIDSON MOTOR CO., MILWAUKEE, WISCONSIN

Hiarley-Davids@una “Corlds Champion™

~ Te ee ea

J ibs eee eC wies; One ManS hws 40 Cords a Day At a Cost of 1 4c a Cord! | 327 size logat thezateot afoot a minute, ||| o> fl Send today for Big Special Offer and Low | moved from log to log or cut tocut as any P 4 dof, Gig a Direct Price on the OTTAWA, the One-| wheelbarrow. 4-Cycle Frost Proof En- Man Saw, the first made and sold direct | gine has balanced crank shaft—pulls over from factory touser. Greatest laborsaver | 4 H-P. Magneto equipped; no batteries and money-maker ever Tor Saws | needed, Special Clutch jever controll- edenables you [7 *-*- “oS AW tostartand stop saw with en- — . Automatic Speed Cuts Down Trees Gove rnor. vasy to move, costs Level with Ground Cuts Down /s Down Trees—Saws OG By cna. less to operate. When not saw- gving No ing, engine runs pumps, feed Stump. Patent Sent For mills and other machinery. Pulley furnished. , Cash or Easy Payments Shipped direct from factory. 30 Days Trial No waiting—no delay. Let the ‘ —— OTTAWA saw your logsand pay . “for itself as you useit, 10-YEAR GUARANTEE. See the OTTAWA at work on your farm once and you will never give it up. Thousands in use, ‘every owner a booster. Out-saws any other on the market, Send today for FREE BOOK and Special Offer. y OTTAWA MFG. CO., 1805 Wood St., Ottawa, Kans<

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RE-PRACTY MEN ooo MAKE MONEY! Hundreds Have Found Greater Income and Prosperity Through This New Profession. The Hovey System of Tire-Practy is the surest, quickest and easiest way to learn the tire repairing business. This complete and easy -to-follow training system has standardized the tire repairing practices of the world. It has been recognized and recom- mended by the majority of the coun- try’s biggest tire companies. It Goes Right to Your Home The Hovey System brings to you a knowledge of the best practices for effect- ive and profitable tire repairing. It goes’ right to your home. Simple charts and clear diagrams make every ~~ of the way to a profitable business easy and pleasant to follow. It shows you how to repair all makes of cord and fabric casings, tubes, pneumatic truck tires, bicycle tires and motorcycle tires; it gives you busi- ness-building plans and systems. It makes you a profit-making link in the chain of The Hovey System is world-widein operation. Write today for plan booklet Dept. 3 THE HOVEY EXTENSION SCHOOL Akron, Ohio, U. S. A. Hovey Tire-Practy stations. | i} | ld Town aes N “Old Town” rests as lightly on the water as a sunbeam. The _ faintest pressure of the paddle gets instant response. It is so steady that rips and white water can be shot with ease. There is a built-in strength to every ‘‘ Old Town Canoe” that makes it give many years of service. But the Sponson Model for the chil- dren—it is safer than a row- boat. Write for catalog. 3,000 canoes in stock. $67 up from dealer or factory. OLD TOWN CANOE CO. 1194 Main St. Old Town, Maine, U. S. A. [2Months toPay. \ ~~ “le cia Mead Devt company, Sr at once #— for the ak monthly ayments on ‘Our ‘ay- §B)\ men ‘arents often mavens first — | ment to hel ehels boys along. ect RY = RID wholesale prices. hree b model factories. 44 Styles, col- 5 }— an i famous Ranger | Yor \' express prepa BO DAYS TRIAL. Selarr bieycle and ‘terms that suit Bea, or easy pa: ymen ho ires =" equi hg half relsperts and Pree hee LX. ys = Snot write a today for bi big pric Va allow the water or soil to injure the floor or carpet. If you have some old window-frames - with glass panes, the box may be con- structed to fit these, the dimensions figured accordingly. A good depth for this starting-box is 4 in., while the front side of the box is 6 in. to allow for the inclined secondary bottom under the real bottom. This box should be made 12 in. wide by 24 in. long, and fe INCLINED BOTTOM~—— Now is the time to start the vegetables grown from seeds. Build a starting- box as here described may be separated into two or more compartments. The window-frame should be secured to the rear edge of the box by means of hinges. This box kept on a shelf in the south window will grow seedlings quickly. When well started, they should be transplanted to a transplanting box.—F. E. BRIMMER. Here’s a Tool for Placing Wild-Animal Traps HE accompanying sketch shows a simple and efficient type of trap placer that will be appreciated by every trapper. It will be found handy for placing traps under water at rat holes, and eliminates the necessity of wading out into the water or using a boat. Its value for placing traps far back into skunk dens will also be seen. All trappers know that the fox, HANDLE SPRING ~\ ) Rivets? 1/2" PIPE. The tool here shown is intended for safely placing traps under water or in places hard to reach although sensitive to human scent, does not object to clean, odorless steel. The sketch shows the construction. A piece of 14-in. pipe is sawed along the center for about 6 in. and the half of each end cut off. The piece that remains can be flattened and bent. A file should be used to trim off the burrs and round the edges. The jaws and handle are made of one piece of flat strap-iron wide enough to go through the pipe without binding. The ends are bent to correspond with the pipe ends. A spring to hold the jaws open ready for action is fastened with rivets, one on the movable handle and the other on the pipe.—FRANK W. HARTH. 94 Popular Science Monty a HIS book, “The Days »f Be: Real Sport,” illustrat. d YES by Briggs, the cartoonist, and . containing a red £ , _Dlooded story of boyhood fishing days, will est sent FREE to every sportsman. Learn of the pleasure, ex- citement and thrills which bait casting angling gives—enjoyment you can have. © sitting still waitien for them to bite. k shows full line of South Bend Baits and Reels. A postal gets it FREE. SOUTH BEND BAIT Co. 14507 High St. South Bend, Ind. Gy “ccc cece W Fei. BW hy was Wr! Fg "FE Cri 1 The masterpiece ofwatchman- / ufacture—adjusted to the escond, temperature and iso- . Encased at factory into your choice of the exquisite new watch cases. The great Burling- ton watch sent on request. Pay at rate of $5.00 a month. You Day only yy rock-bottom price—yes, Z bottom price —the invest 5 which the a ay ia sol e color tilustra- Write Today ff tions of all parent designs in aa «el = wodad have to choose from. address on ‘0 rice at Sth St. ~~ -» Chica oe —— Canadian Office: 338 Portage Avenor. Winnipeg, Man. oy! Build This Car This nifty litt! driven by gas motor can be showing how tc build this lad’s SYPHER MFG. CO., 174 Sypher Bidg., Toledo. Ohio , SAVE 25% to 60° rd ly used GRAFLEX-KODAKS Cameras and Lenses of every description Equal to new. Save money. Write now for Free Bargain Book and Catalog li sting hundreds of money- eave | bargains in sligh' & y used and new supplies. al 3 goods sold on 10 days’ Free Trtal. ack if not a ou_ take no chanc: dealing with We have been in the phot graphic pusinene over 19 years. Write now. CENTRAL CAMERA CO., Dept. 64, 124 S. Wabash Ave., Chicago HB BATTERY CHARGING PAYS $150 TO $300 EVERY MONTH Start your own business NOW, No electr cal knowledge needed. Small cash payment brings you any HB Charger,balance on long ener. terms. Money-bac guarantee. Write TODAY for information. HOBART BROTHERS COMPANY Box $47, Troy, Ohio Brings You Balance Fasy Terims Small ¢ > Payment HB y ‘he arger any Send today for illustrated book about our ‘Canoes of Quality” mailed to any address, post pai KENNEBEC BOAT AND CANOE co. 9 R.R. Sauare, Waterville, Maine. FREE E CATALOG AUS AND NUMBER IN CLASS. Either pin fllustrated made with any 3 letters and 2 ficures, one or two colors enamel. Silver plate, 25@ ea., $2.50 doz. Sterling silver, 50% J /EGs2 oon $5.00 doz. Write for new catalog. . BASTIAN BROS, CO, 287 Bastian Bidg., Rochester,N.Y, WHY insects? I buy not spend Spring, Summer and Fall — butterflies, hundreds of kinds for collections. Some worth $1 to $7 each. Simple outdoor work with my instructions, pictures, price list. Get posted now. Send 10c (NOT STAMPS) for my Illustrated Prospectus. Mr. SINCLAIR, Dealer in Insects Dept. 7, Ocean Park, Calif. eee April, Easy Monthly 30 For tk eral b Oak a the ce Many yur ple ofour ly pay? § ym Instru wheth the 8S: can p Write Lat

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Easy Monthly ma 30 Cents a ine Pays For the mellow-toned Symphonic Piano. Sev- eral beautiful models in genuine Mahogany, Oak and Walnut. Guaranteed 25 years. Sold the celebrated Larkin Factory-to-Family Way. Many music lovers have saved $100 and more, )ur plan permits 30 days’ trialin yourhome, Up to four years’ time, nointerest. Convenient month- ly payments. Ask for FREE Catalog showing “ . ms Also Player Pianos Symphonic Pianos *"323°¢%,2is Instruments in actual colors. Please state whether interested in the Symphonic Piano, the Symphonic Player Piano (which anyone can play) or the Symphonic Baby GRAND, Write now for your Catalog. Larkin Solos: DeskPPSM-421 Buffalo, N. ¥

How to Win Success in Band /; and Orchestra Ltr. RYOR, Sousa and a eight other world-famous musicians tell secrets of their success. How you can quickly learn saxophone, cornet, trombone—any instrument youchoose. . P 66 9 Cultivate Your Musical Bump Double Your Income with a CONN Built in world’s largest factory. Used by all great artists and finest bands and orches- tras. Superior in tone, tune and mechanism. FREE TRIAL and Easy Payments Cornet, saxophone, trombone, clarinet— any band and orchestra instrument. guarantee bond with every Conn. Send postcard today for details and your copy of success book, instrument that interests

Mention you. Ce ney gy eon mr STATIONARY ENGINEER TRAFFIC MANAGER Marine Engineer Railway Accountant Ship Draftsman Commercial Law ARCHITECT GOOD ENGLISH Oommon School Subjects CIVIL SERVICE Railway Mail Clerk AUTOMOBILES Spanish Teacher | )Banking Contractor and Bullder (JArshitectaral Draftsman Concrete Builder Structural a. PLUMBING AND HEAT Sheet Metal Worker Mathematics Textile Overseer or Supt. A rctittirene OHEMIST a > Pharmacy Poultry Raising Name

Business Address — Present Occupation Street and No.

City State Canadians may send this coupon to International Correspondence Schools Canadian, Ltd., Montreal, Canada

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i@ pair method is mak- ingmen RICH! Chas, week in shop -» age 62, learned TIRE SURGERY, has shop in small town, writes: ‘‘Cash receipts for May, June and July, 1920, $30,000.00."" E is easy to learn. I will teach you in two weeks, Within thirty days you're started on road to fortune. Car owners EVE HERE demand this NEW repair meth- od, as it DOUBLES life of Tires. 28 million tires wear- ing down DAILY. ONE THOUSAND MORE Tire Sur- ; epope needed ped N can succeed ly. A It’s. a SHORT, EASY ste n —the field that bas made men . put $6,000.00 in bank for John W. Blair, Ohio, in 12 months; got $8,000.00 for Fleming, of New Zea- land, within 1 done same for , ¥ “a Investigate! 9 tails. Send coupon book, Bx Mr. Haywood, Pres., Haywood Tire & Equipmen e 2 1275 "Capitol Ave., Indlanapolls, ind. — Deer Sir: Send full details of Tire Surgery, as I want @ to get into big paying business quickly, Name ; Address_ It’seasy. We show 2 you how. Furnish lumber, fittings, hardware, accessories and complete simple plans. You assem- ble and finish. Hammer, brace and bit and screwdriver only tools required. Need no shop. No experience. No skill. Send for free circular. Shows choice of Phonographs, Lamps, Cedar Chests te and Morris Chairs Buildstronger and betterthan store goods at less than half regular prices. Our free circular tells how easily you can build them. How youcan save money. How you can make money. Thousands of men—plumbers, printers, clerks, office men, ete.—busy every evening turning spare moments into money. They are building useful and attractive articles for their own homes; also for friends, You will like this pleas- ant and profitable work. Get started at once— send coupon—we’ll send circular ‘‘D’’ free by return i ee to ee ae ae mail. Address Vocational Supply Co. 423 E. Willard St., Muncie, Ind. Vocational Piease send me your free circu- Supply Co. lar ‘‘D’’ and full details of your Proposition. ee Address Ty _ - SAVE 25% to 65% on Slightly used and Rebuilt Motor- cycles, Side Cars, Johnson Motor « Wheels, Evans Power Cycles, Bicycles. = Send for Free Bargain Bulletin and Money Saving Message, listing hun- © dreds of Bargains in used, rebuilt and - new machines,supplies, accessories, etc. sit sis sak AMERICAN MOTOR CYCLE Co. Dept. 402, 2047 W. Chicago Ave., CHICAGO Write the Words for a Song We write music and guarantee to secure publication by a New York Music Publisher Our Lyric Editor and Chief Composer is a song-writer of national reputation and has written many big song-hits Submit poems on any subject. We examine them free. BROADWAY STUDIOS 249 Fitzgerald Building Broadway at Times Square New York, N. Y, Arithmetic of Electricity A practical treatise on electrical calculations of all kinds reduced to a series of rules. $1.50 Postpaid. Popuiar Science Monthly,225 West 39th St., New York Motorcycle Bar ains ..«@%! Z pal stay) screwing in a larger threaded sleeve tapped for the screw. Paper, fiber, or wood faced pulleys all have a higher frictional coefficient than iron or steel. A strong small pulley is seen in Fig. 6. A hard wood hub is driven into a piece of pipe, drilled for the shaft, and the pipe turned and crowned for a pulley face. If a drive fit is made on - -- CCT dddibbuedcey --| ’ _. SSS —— | | ot ole aS eS ~ e CLL FIG.6 If a particularly strong pulley is re- quired, use one of these three types FIG.7 the shaft and treated with shellac be- fore being driven on, no set screw will be needed. Another type is shown in Fig. 7, where a narrow wood or metal hub is driven into a pipe coupling and two pipe ends tightly screwed up against it and cut off, the face and ends then being machined. In Fig. 9 is a sleeve with flange to which any sized wood pulley may be screwed or bolted.—H. H. PARKER. Forcing Oil from a Barrel by Air Pressure GOOD garage method that saves pumping oil to each customer is to use the free air pressure to force the oil into the measure by simply turning on the air-cock. Take two old spark-plugs and re- move the porcelains. Through one plug shell run a copper tube that is a snug fit and bend the top portion over in a semicircle so that it points down as shown. The long end should reach nearly to the bottom of the barrel. Solder around the plug bushing and the IR, INLET AIR LET. PIPE EXTENDS NEARLY TO ~ BOTTOM OF BARREL When the cock of the inlet pipe is opened, the compressed air will force the oil out of the pipe tube. Solder a valve stem in the top of the other shell as shown. Then screw the plugs into appropriate holes in the barrel head, and connect the plug with the valve stem with the air supply, placing a shut-off cock in the pipe at a convenient point. By turning on the air-cock air is forced into the barrel, which forces the oil out of the long tube into the meas- ure. As soon as the air is cut off, the valve-stem automatically shuts off any further pressure.—L. B. ROBBINS. 96 Popular Science Mont)’, FASY to do and at low cost. Your old “foot power’’ bicycle can be quickly transformed to a speedy, easy-run- ning high power Motorcycle with the Shaw Motor Attachment. No third wheel! Fits any men’s bicycle of any make or size, Chain drive model can be attached in less than an hour. A boy can putit on. No special tools or knowledge necessary. SHAW Mt... Thousands in use. A light weight 2}4 H-P motor of wonderful efficiency. Simple to attach. Everything furnished complete. Every owner enthusiastic. All materials are guaranteed. Get one NOW. FREE Write at once for Free Book and Low Direct Factory Price on the Shaw Attachment, also the Shaw Motor-bicycle--a complete power machine at a low price. SHAW MANUFACTURING CO. Dept. 1464 ' Galesburg, Kansas Learn Music At Home! New Easy Method Piano, Organ, Vio! XY Drums wend Traps, Sax 4 ophone, Flute, Clarir y Ukelele, Trombone,Corn Guitar, Banjo, Mandoli Harp, ‘Cello, Sight Singir No longer need the ability play be shut out of your li Just write us a postal toda for our new Free Book, fr from the printer. Let us t you how you can easily qui ly, thoroughly learn to p your favorite musical instr ment by note in your ow! mS home, without teacher, by our . New Improved Home Stud Method, without paying a cent for lessons! Different, easi than private teacher way—no tiresome, dry exercises inconvenience. No-trick music, no “‘numbers,"’ yet simp! wonderful, amazingly easy for even a mere child 250,000 Pupils! We have successfully taught over 250.000 people, from seven to seventy, im all parts of the world! WHundreds write “Have learned more in one term in-my home with your weekly lessons than in three terms with private teachers.” “Everything is so thorough and complete.’ ‘The lessons are marvels of simplicity. My 11-year old boy has not had the least trouble to learn.” Wonderful New Book Free! We want to have one pupil in each locality at once to help advertise our wonderful easy system of teaching musi For a limited time, we therefore offer our marvelous lessons at practically no cost. Charges amounting merely to about the cost of sheet music, postage, etc. Beginners o: advanced pupils. We have hundreds of pupils right here 1 New York, the musical center of America, who prefer our Home Study method in place of best private teacher. Get all the proof, facts, letters from pupils, amazing offer and fascinating New Book just issued, all free! Write postal to day. Address U. S. School of Music, 84 Brunswick Building, New York Experiments With 110- Volt Alternating Current - By J. D. ADAMS Here at last is a book that develops a prac- tical working familiarity with the alternating current—the form in which electricity is used in every home. The author shows how this can be done in an interesting and inexpensive way. The only way to gain a thorough understand- ing of electricity as it is used commercially is by direct personal experiment. The knowledge thus gained is of vastly more value and im- portance than that acquired from the perform- ance of the stereotyped series of battery exper- iments so uniformly described in the text-books. 256 pages, 135 illustrations Price, postpaid, $1.75 POPULAR SCIENCE MONTHLY 225 West 39th Street. New York City Bayt M: 4 du for dr protec and ¢ indi such provi was O such hardl: proter But that | form canve excell the n allow rathe moto: ing is Tw are Cc semic ter as are fc toget exten the e arour A drawi edge illusti come: enfor Thi ring aroun pose, fit ar Wires botto holes conve Pro small from protec drawr to pr coils.-

Page 79

» ing Se.

simp! n seven vrite h your chers.”’ lessons 1ot had e! to help musi lessons rely to ners Or here in fer our r. Get fer and stal to ew York 1 0- ent prac- nating is use w this pensive stand- ally is wledg e

aE

fi} ril, 1921 Place Protective Covers Over Small Motors MALL electric motors installed in dusty places, especially those used {or driving grinding-wheels, should be protected by covers to keep the dirt and dust out of the bearings and windings. For a heavy-duty motor such a cover might be made of sheet iron, but air ducts would have to be provided for cooling unless the motor was of the totally inclosed variety; in such a case, an extra cover would hardly be required except perhaps to protect the bearings. But for the ordinary small motor that is the object of this article, used for more or less intermittent service, a canvas or other cloth cover provides excellent protection from dust, while the material used is porous enough to allow some ventilation. Canvas is rather heavy, except for a good sized motor, but cheese-cloth or flour-sack- ing is about right. Two end patterns and a side piece are cut out, the end pieces having a semicircular top about the same diame- ter as the motor housing. The edges FOL & STITCH UREINFORCING RINGS~ { \

COMPLETE COVER

ie BINDING CORDS FOLD & STITCH wae eo oes & Oe we ceese es ee eeeeero lod PULLEY END COLLECTOR RING END

' | ' ' et ee lin AE, Sich LE Ral dnt hii clink Ect Rms: SIDE PIECE

You cover your typewriter, but leave your motor exposed. Make a cloth cover for it are folded over and the cover stitched together. It should be long enough to extend below the motor base so that the edges may be bound with a cord around the base of the motor. A good plan is to incorporate a drawing cord in the lower turned-over edge of the cover, as shown in one illustration. The hole where the shaft comes through requires to be re- enforced. The illustration above shows a ring of thin leather or felt stitched around the shaft opening for the pur- pose, and the ring should make a close fit around the shaft. The connecting Wires may be either led in under the bottom of the cover or two reenforced holes may be put through it at any convenient point. Provided with a cover of this kind, a small motor can be kept clean and free from dust while the bearings are well protected and enough air will be drawn through the meshes of cloth to prevent any overheating of the coils.—H. H. PARKER. “Reduced *S-O0O SHOES

W. L. DOUGLAS Quality of Material and Workmanship Maintained “Resi Worcmnny 10.00 || “RES Sabucte’ °6.00 FOR MEN AND WOMEN THE STAMPED PRICE IS W.L. DOUGLAS PER- SONAL GUARANTEE THAT THE SHOES ARE ALWAYS WORTH THE PRICE PAID FOR THEM YOU CAN ALWAYS SAVE MONEY BY WEARING W. L.DOUGLAS SHOES SOLD DIRECT FROM FACTORY TO YOU AT ONE PROFIT

<< They are the best known shoes in the world. Sold in 107 W. L. Douglas stores, direct from the fac- tory to you at only one profit, which guarantees to you the best shoes that Mican be produced, at the | lowest possible cost. W.L. Douglas name and the retail price are stamped on the bottom of all shoes before they leave the factory, which is your protection against unreasonable profits.

W.L.Douglas shoes are absolutely the how shoe values for the money in this country. They are made of the best and finest leathers that money can buy. They combine quality, style, workmanship and wearing qual- ities equal to other makes selling at higher prices. They are the leaders in the fashion centers of America. The prices are the same everywhere; they cost no more in San Francisco than they do in New York. SHOES FIT WELL AND HOLD THEIR SHAPE W. L. Douglas shoes are made by the highest paid, skilled shoemakers, under the direction and supervision of experienced men, all working with an honest deter- mination to make the best shoes for the price that money can buy. CAUTION penn see in Name and price is plainly stamped on the sole. Be care- ful tosee that it has not been He or mutilated Héo sident y, W. L. Douglas Shoe Co., 124 Spark St., Brockton, Mass. ee itn

W.L.Douglas shoes are for sale by over 9000 shoe dealers besides our own stores. If your local dealer cannot supply you, take no other make. Order direct from the factory. Send for booklet telling how to order shoes by mail, postage free.

Dollars in Hares We pay $7.00to$18.50 and upa pair and express charges. Big Profits. We furnish guaranteed high grade stock and buy all you raise. Use backyard, barn, cellar, attic. Con- tractand Illustrated Catalog Free. Bd FOOD AND FUR Bd 407C Broadway New York

Electrical and Mechanical Engineers receive fabu- lous salaries. Thousands wanted. We give you thorough personal training from 3 months to 2 years under expert instructors. NOT A TRADE SCHOOL but a PRACTICAL, TECHNICAL COLLEGE teaching electricity, steam, gas, auto- tractor, armature winding, drafting, Extensive labora- tory and shop equipment. DEGREES AWARDED. Day and night sessions: enroll any time. Write for free catalog. Earn-while- -you-learn-plan. FINLAY ENGINEERING COLLEGE 1002 Indiana Ave. Kansas City, Mo.

Print Your Own cards, circulars, labels, tage, _menus

book, paper, Press $12. Li Press €1 ai k UTS EXPE NSE INHALT v ALL OUTLAY. Pays for _ if in short time. Will last for years. Easy to use, printed rules sent. Print for others, BIG PROFIT, Write factory TODAY for press catalog, TYPE, cards, paper,envelopes. THE PRESS CO., 0-33, Meriden.Conn.

You can make from $1 to $2 an hour writing show cards in your spare time, quickly and easily learned by our new simple method. No canvassing or soliciting. We sell your work and pay you cash each week. Full particulars and booklet free. Write today. AMERICAN SHOW CARD SCHOOL 206 Ryrie Building, Yonge & Shuter Streets, Toronto, Canada

An Honest Serviceable 8000-Mile Tire—This casing is not sewea, patched or retreaded but is rebuilt throughout of new material,

Reinforced

side walls and a Standard Non-skid tread of new Jive rubber. same as cut. Actually guaranteed for 5000 miles against defects in’ materials and oe High Grade Tube Free With Each Tire Ordered 28 x3 $ 7.15 31 x4 ..$10.80 32 x 414. .$12.40 36 x 41%. .$14.35 30 x 3 7.85 $2x4 .. 11.15 33 x 4%. 1. 12.95 35x65 .. 15.35 30 x 3% 8.95 83 x 4 ae 34 x 44.. 13.60 $37=x5 .. 15.45 32 x 3%.. 9.55 84x4 11.9 55 x 4%.. 13.85 State straight side or clincher. Send 32.00 deposit with your order, Tire will be shipped C. O. D. with section left unwrapped for examination. If tire is not satisfac- tory, deposit will be returned. 5 per cent ciscount + oS. amount is sent with order, DURABLE TIRE AND RUBBER co. , Wabash Ave.. Chicano, tll.

97

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COURSE IN TWO YEARS You Want to Earn e | Big Money! )} And you will not be satisfied unless | you earn steady promotion. But are § i you prepared for the job ahead of ff 4 you? Do you measure up to the standard that insures success? For i! a more responsible position a fairly | i) good education is necessary. Towrite } a sensible business letter, to prepare } estimates, to figure cost and to com- pute interest, you must have a certain i} amount of preparation, All this you | must be able to do before you will earn promotion, — Many business houses hire no men whose general knowledge is not equal to a high school course. Why? Because big business refuses to burden itself with men who are barred from promotion by the lack of elementary education, Can You Qualify for a Better Position? We have aplan whereby youcan. We can give you a complete but simplified high school course in two years, giving you all the essentials that form the foundation of practical business. It will prepare you to hold your own where competition is keen and exacting. Donot doubt your ability, but make up your mind to it and you will soon 4 havethe requirements that will | bring you i success and bigmoney. YOU CAN DOIT. ff Let us show you how to get on the road *o success. It will not cost you a single working hour. We are so sure of being able to help you that we will cheerfully return to you, at the end of ten lessons, every cent on sent usif you are not absolutely satisfied. hat fairer offer can we make you? Write today. It costs you nothing but a stamp. AMERICAN SCHOOL a a Drexel Ave. & 58th St., Chicago IIIB MASS iineeten Ye rere) (p canal Lawyer $5,000 to $15,000© Dept. H-475, Chicago, Ill. Expiain how I can qualify for position checked: «+»... Architect#5,000 t015,000 a Buildin Contractor sal Mechanical Engineer eoecee: Automobile Engineer €4,000 to $10,000 to $10,000] -+++- Shop Superintendent ° spied Automobile Repairman #3,000 t 0 $7,000 to $4,000 Employ eves Civil Engineer © $16,000)... Steam Eagineet ereeed Structural Er Engineer 000 to $4,000 to $10,000). Foreman’ s Course vv Business ian ace 5,000 000 to 84,000 @ -.Certified Public: Ae menus Sanitary Engineer s,000ff countant $7, emabiatae * & yor sn Telephone eBagincer 8 to $7, «Draftsman & Designer'!----.- eens . safuoes 500 to $4,000 $2,500 to $5,000 ... High School Graduate ° In two years ii Fire Insurance Expert In one year $3,000 to $10,000 Cemcacascene esas ment N 8 j $4,000 = $10, 0006 | Wedges Used in Place of Carpenter Clamps FLOOR lamp was being con- structed and it was necessary to have clamps at least 5 ft. 6 in. in length, and the longest clamp that was in the workshop was only 5 ft. long. Two wedges happened to be Ingenuity helped to accomplish a diffi- cult job without a clamp of sufficient length lying on the floor near by, so we used these wedges instead of clamps. We placed the lamp upon the work- bench and arranged it as shown in the accompanying figure. As the ceiling was very low, we wedged the lamp be- tween the work-bench and the ceiling, and the following morning we removed the wedges and found that we had a perfect joint.—JAMES O’CONNOR. Substituting a Pencil Clip for a Ruling-Pen HOSE who have tried to rule lines with the help of the undercut side of a common foot-rule, know that the method is likely to result in blots upon the work. A bet- ter way is to slip a five-cent pencil clip over the end of the pen and \—Pt rule the desired lines by drawing the ball of the clip along the edge of the ruler. The clip can be used on an ordinary pen or on a fountain-pen, as shown in the illustration, but it cannot, of course, be used upon a fountain-pen having threads for a screw-cap upon the pen end of the holder. 98 A pencil clip on your pen makes it a ruling-pen honesty of — Popular Science Montli/, Sas Coon ; J si ; DIAMONDS = 27 WIN HEARTS se ( A ye Sixty-Three Years. iB FSH | Confidence in the — our great leader at ’ : ‘0 $20 Down $10 a Month Also special] bargains in other new engraved lowest prices. \, wieveed et, and pe Wh SEND mon allieres, Bar FOR Catalog \Z "scart Ear Screws. Whate lect. carf Pins, Watches, will be peut, prepaid. Waist Watches 8, i. \. “e ° . ds hands. | satisfied pay NS Accepted one-fifth of urchasepriceand a keep its balance = eq power enables us \ to make the very Monthly paymen Ing Cities LOFTIS BROS. & Co. THE | NATIONAL CREDIT JEWELERS 108 N. N. State St., Chicago, ill. i in a Gordon Motor Crib. More pleasure for you when ' motorin with baby tucked snugly in this convenient crib. e safest way, the doctors say.’’ Crib easily strapped in any touring car. ears arrangement | ab- sorbs all shock over roughest roads, Hood when raised protects against weather. Fold crib flat or detach when notin use, Sold everywhere or sent parcel post prepaid. Send for illustrated booklet and dealer’s name GORDON MOTOR CRIB CO. 219 North State St., Dept. 38 CHICAGO Learn to dance at home through wonderful aew meth- od. Detailed instructions of the newest dances are taught by America’s foremost au- thority on Ballroom Dancing. Sample lesson 25c cadditional lessons 50¢ each. The instructions are remark- ably simple and easy to under- stand. Send 25c for sample lesson. A.M. SYSTEM OF DANCING INSTRUCTION Dept. 44, 290 Broadway, New York Perfect hearing is now being re- stored in every condition of deaf- ness or defective hearing from causes such as Catarrhal Deaf- ness, Relaxed or Sunken Drums, Thickened ome og Roaring and NN Hissing Sounds, _ Perforated, E Wholly or Partially Destroyed Drums,Discharge from Ears, etc. Wilson Common-Sense Ear Drums “Little Wireless Phones for the Ears*’ require no medicine but effectively replace what is lacking or defective in thenatural eardrums, They are simple devices, which the wearer easily fits into the ears where they are invisible. Soft, safe and comfortable. Write today for our 168 page : FREE book on DEAF: Have Baby Comfy : . giving you full particulars and testimonials. WILSON EAR DRUM CQ., Incorporated 541 Inter-Southern Bldg. LOUISVILLE. KY. al pril Gett metal marg! any Pp loose the d is les safety marg Th show show: bolt i strail a 3 this ] maxi! be ut A bo its t are point Tr as it appli as st It is hig. the k Hov H acros ing i till I to be h: hard s al; simil wher the a abso Ts plece wast first Wate piece and the ao), mod stirri

Page 81

April, 1921 Getting the Most Out of a Screw or Bolt HE maximum strength that a rod, screw, or bolt will have at the point of greatest strain depends on the cross section at that point. To illustrate-—-suppose we find that .-in. bolts are required to bind two netal parts together and still have a margin of safety which will prevent any possibility of the two parts tearing loose or the sheering of the bolts. If the diameter of the bolt cross section is less than 14 in., then the margin of safety will be nil, or if there is any margin at all, it will be very small. The accompanying _ illustrations show this point graphically. Figure 1 shows how the greatest strength of a bolt is obtained. The point of greatest strain in this case is the sheering point, A. By having the threads begin at this point, say one or two threads, the maximum cross section of the bolt will be utilized, thereby insuring maximum strength at that point for the given bolt size. Figure 2 shows’ by cross-section how the max- imumstrength of the bolt is utilized. The bolt complete- |

ROOT DIA. FIG3 FIC. 4 A bolt is only as strong as its thread-root diameter hole. are allowed to cross the point, A. The old saying, “A chain is as strong | as its weakest link,” may be aptly | A bolt is | applied to the threaded bolt. as strong as its thread-root diameter. It is plainly evident that. the bolt in tig. 4 cannot possibly be as strong as the bolt in Fig. 2..-fRANK W. HARTH. How to Mend Holes in Hard Rubber Goods AVING a hard rubber triangle, one side of which was broken across, I tried various ways of repair- ing it, but without satisfactory results, till I tried the following, which proved to be the only satisfactory cement for hard rubber that I have ever seen. It is also suitable for use on celluloid or similar compositions, or in any place where liquid glue is used, possessing the advantage over the latter that it is absolutely water-proof. Take some scraps of celluloid—a piece of an old celluloid comb or old waste photo films (the latter being first cleaned of the gelatin layer by hot | “ater and soda)—cut or break in small pieces, place in a wide-mouthed bottle, and just cover with glacial acetic acid the lower grade ‘‘No. 8” acid will not do), cork the bottle tight, and set in a moderately warm place to dissolve, stirring occasionally. This may take

ly fills the | Figure | 3 shows a bolt | whose threads | shearing |

On the Basis of Facts The life of our country is built around its Public Utilities. Our social, in- dustrial and Government activities could not exist today without the contin- ued operation of their in- dispensable services. That such services may be extended and developed to be of the greatest use to the greatest number, the Federal Government and practically all the states have appointed Public Service Commissioners as permanent tribunals to regulate public utilities with fairness to all concerned.

8 & One Policy “eciaren © oc Facts as to the past and studies as to the future, the Bell Companies find are es- sential to the proper man- agement and development of their business. This in- formation is open to study by these Commissioners and through them by the public generally. The solution of the prob- lem of building up and maintaining the public utilities, which is of the greatest importance to the people of this country, is assured whenever all the facts are known and given their due weight. AMERICAN TELEPHONE AND TELEGRAPH COMPANY AND ASSOCIATED COMPANIES One System

vertising Posters and Glass Signs

ful 50-lesson course includes individual instruction by correspondence from expert artists; total cost only $15 erine’’ colors and brushes —FRE and $1 wee enty for 12 weeks. ener cusrsoteedo or mo 1 aN refund- ed. Earn enough first week to pay for course. Send TO Empire AB lastibete, 2050 Amsterdam Ave., New York, N. Y.

Make $10 to $25 daily! Make Show Cards, Signs, Ad- Big demand! Inter- esting, profitable profession. Easy to learn in few weeks by unique, novel method; something new! Our wonder- Every student given $15 5h aa of finest **Mill- soa nsme and address and D 0 ore ae fo hone and on arrival

will interest you. I offer to spare time, at home

ACCURATE All calculating problems solved ina flash by this marvelous new machine. Automati- cally adds, subtracts, multiplies'and divides. Shows results instantly. A whirl, _— SPEEDY = speed infallibly accurate. Work equals $350.00 machine. Used by S xov't and largest corporations. Guaranteed in writing for three years W rite LATEST TOD: AY for attractively illustrated booklet and liberal FREE TRIAL OFFER. MODEL RAY ADDING MACHINE CO., Grand Rapids, Mich.

GRRE EERE Eke EEE

99 Universal Service And all directed toward Better Service Learn Mechanical ea EARN $35 TO $100 A WEEK Are you earning less than this amount? If so my ) give you a thor« oan DE tical training in me chani al drawin x by mail Course includes highe ‘ se! of instruments and « draftir ng equipment "Taner an i tee to give you a thorough, practic cal trair ing that qualifies for a high salaried po nas a professional draftsman My arad uates making gor oad with Bix oncern everywhe re Write for fre 0 okot intormation * Future ir : Drafts iz.’ aa: Dee, dpe Ro COLUMBIA SCHOOL oF DRAFTING h & T St., Was Rington, D: c “ADD:SUBTRACT:MULTIPLY: DIVIDE: ADDING MACHINE

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‘Jirst aid in every householo —Musterole Cough, cough, cough. How it racks little Dorothy and passes on to mother and grandma and holds a croup danger for all the little ones! Hurry, there, with the Musterole, that pure, white ointment that is better than a mustard plaster—and it will not bring a blister. Massage it gently over the chest and neck. Feel the tingle, then the cool delightfulness as Musterole searchesdown. It will penetrate, never fear. It will rout that old congestion clear away. Musterole is a pure, white oint- ment made from oil of mustard and afew home simples! Muster- ole searches in under the skin down to the heart of the conges- tion. There it generates a peculiar congestion -dispersing heat. Yet this heat will not blister. On the contrary you feel a relieving sense of delightful coolness. Rub Musterole over the spot. And you get relief while you use it; for Musterole results usually fol- low immediately. On no account fail to have a jar of Musterole handy. For coughs and colds and even the congestions of rheumatism or lumbago Musterole is wonderful. Many doctors and nurses recommend Musterole. 35c and 65c jars—$3.06 hospital size. The Musterole Co., Cleveland, Ohio BETTER THAN A MUSTARD PLASTER Play the Hawaiian Guitar Just Like the Hawaiians! Our method of teaching is so simple, plain and easy that you begin ona piece with your first_lesson. In half an hour youcan playit! We have reduced the necessary motions you learn to only four—and you acqufre these in a few minutes. Then it is only a matter of practice to ac- juire the weird, fascinating tremo- los, staccatos, slurs and other ef- fects that make this instrument so delightful. The Hawaiian Guitar plays any kind of music, both the melody and the accompaniment. Your tuition fee includes a beauti- ful Hawaiian Guitar, all the necessary picks and steel bar and 52 complete lessons and pieces of music. Special ar- *‘ 3 rangements ior lessons if you have your own guitar. Send Coupon NOW Get Full Particulars FREE First Hawaiian Conservatory of Music, Inc. .233 Broadway, NEW YORK I am interested in the HAWAIIAN GUITAR. Please send complete information, special price offer, etc., etc. ADDRESS... cccrccerccesersceresveecesesesece TOWN AND STATE........----s+s2+02 Write Name and Address Clearly from one to several hours, according $ to the temperature and the variety of celluloid. Don’t get it too warm, or the acid will evaporate and blow the cork out. The solution should have the con- sistence of thick syrup or liquid glue. If too thick, thin with a few drops of | COVER WITH GLACIAL ACETIC ACID CELLULOID SHAVINGS With a solution of celluloid shavings in glacial acetic acid, you can mend broken articles made of hard rubber or celluioid the acid; if too thin, set in a warm place, open, and allow part of the acid solvent to evaporate. For use. Cleanse the surfaces thor- oughly, and apply the cement just as you would liquid glue, using plenty. Bring parts together and clamp or bind as tight as possible. This last is im- portant, to secure a strong repair. Let it set for twenty-four hours to be- come thoroughly hard. On more por- ous materials, where used as a water- proof glue, the time may be shortened considerably, but for hard rubber or celluloid, the full time is necessary, if you want a good strong job. When dry, scrape off the exuded surplus cement. If rightly done, the work will break anywhere else before it will break in the same place again. Keep the cement well corked to avoid any evaporation of the acetic acid.—CHARLES A. PEASE. Popular Science Monthly Every Boy Needs Them To display charts or drawings, or to hang pictures or trophies, there is nothing so convenient as Moore Push-Pins Glass Heads, Steel Points Allowed when tacks or nails are prohibited. The needle points will not mar wood work or walls and no hammer is needed. if ny i Suggest a use and we'll send SAMPLES FREE. | Sold by hardware, stationery, ee drug and photo supply stores | C ou ok pkt. every where MOORE PUSH-PIN CO., 11-4 Berkley Street, Philadelphia, Pa. | Easy to Play Easy fo Pay (4) Containing complete ff story of the origin and history of that wonderful inatru- ment—the This book tells you when to use Saxophone —singly, in quartettes, in sextettes, or in regular band; how to transpose cello parts in orchestra ; and many other things you would (ae like to know. \ + Easy to pay le , MAKES AN IDEAL PRESENT G Send for free Saxaphone book and catalog of every- thing in True-Tone band and orchestra instruments BUESCHER Sete Sere oe. Joye ee Coe Cisebammeay eet PHONOGRAPH A few hours interesting work saves OVER over half and gives you 8 machine to suit your ideas. We furnish HALF motors, tone arms, case material, blue prints and full instructions Plays any record. Make fine profit building phonographs for your friends. , Write today f } anager dt igus FREE AGENTS itiePitnogrnts Choraleon Phonograph Co. 421 2d St. Elkhart, Ind, Make a Protector for the Camp Candlestick O prevent a sudden draft from blowing out the candle make a protector asshowninthesketch. The ordinary candlestick-holder is used and the cup for holding the candle is re- moved and a square block of wood is substituted in the tray or pan. On each edge of the block a clip or thin piece of metal is attached with screws or nails, mak- ing four standards like those used on the regular burner of the kerosene lamp. A lamp chimney is placed in the clips. For a candle-holder a hole is bored in the block, or four nails are driven into the wood around the candle. The small wax candles are used, as they are the best for this kind of a lamp. Such a candle will burn with a steady flame.—CHARLES R. FISHER. Just the thing for your shack or tent on rainy nights 100 (p , Need MONEY? If you are making less than $150 48 fj month, write me today. I have no “get-rich-quick”’ plan. But if you if F \\y 6 6are wide-awake, honest, willing to F E m. work with me and give meat least NOT A CONTEST. We have anew plan whereby we furnish part of your time, I offer you MAN OR WOMAN the Special Agency (local or trav- eling) for our great line of House- hold Necessities. Experience is unnecessary. I will furnish every- thing. so that lack of capital shall not stand in your way. Hundreds of pros- perous men and women who started thie Special offerisopen. Albert Mills, Mgr. 2976 American Bldg... Cincinnati, O. BLANK CARTRIDGE op Well made and ef- fective; modelled on latest type of Revolver: appearance alone is eno to scare a burg lar. When loaded it may e as effective as a real revolver without danger to life. It takes stand- ard .22 Cal. Blank Cartridges obtainable every- where. A Great Protection ins rs, ramps and Dogs. You can have it lying about without the danger attached to other revolvers. PRICE GOc Postpaid: Better e and superior quality for $1.00. Blank cortriges -22 cal., shipped express 5Uc per 100. CHICAGO SPORTING GOODS CO., Dept. 69 CHICAG' cy Factory to Rider ves & to oe. the model you selec Tom es. ' Zed choos of Wanner bicselee Deleens |l on prepaid, direct the Makers ‘tor'30 : Wea on ers for 3 Ten Free bn wheels, chai parts and ires equipment at half usual prices. BIG RANGER CATALOG FREE, with mar- velous new prices, 30 day trial offer and e a Cycle Dept.L109 Chicago Apr T T, ] hothe in p amat nan. By parts oute! easle’ aged, repai dead not t arbol the s anev thea Am. lath new | repla relati origir bette: half i anda drive. often conve It is matic

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ee iia —— ee oe 3 t “4 8 d 1 st D. April, 1921 To Make Wood-Turning Lathe Centers HE conventional spur-and-crotch ]. lathe centers for wood-turning are »othersome things to make and to keep in proper shape, especially for the amateur pattern-maker and crafts- man. By making such a center in two parts, an inner tapered arbor and an outer sleeve, the construction is much easier and when worn down or dam- aged, as frequently happens, it may be repaired without much trouble. The dead center has a sleeve driven, but not tightly forced or shrunk, on to the arbor, so that if the point wears down the sleeve can be driven off again and a new point turned up or ground. Then the arbor is turned or ground back toa Po _ LIVE CENTER Amateur wood-turners should equip their lathes with a live-spur center new shoulder so that the sleeve when replaced will be in the same position, relatively, to the point as it was originally. In the case of the live-spur center, the construction is similar, except that the outer end of the sleeve is filed down so as to form two, three, or four spurs, as desired. A solid spur center is rather difficult to make, especially as the point should run true; but by having the spurs on a separate sleeve and the point on the central arbor, this difficulty is obviated. The spur sleeve must be driven on to the arbor rather tightly, so as not to slip; or, better yet, a small hole can be drilled half in the sleeve and half in the arbor and a round key driven in for a positive drive.-—H. H. PARKER. An Illuminated Writing- Board for Inspectors ETER inspectors and others who J are obliged to record readings often in dark places will appreciate a convenient illuminated writing-board. It is easily made and is lighted auto- matically by a pocket flashlamp. A piece of oak 1 0 in. by 6in. by 14 in should be used for the board proper. At the center and top of the board another piece of wood is fastened to make a base for the light. The flashlamp is bound to the board by a section of sheet brass, A, 1/64 in. $e - aaah sent - eat ah, et ee t en -¢ quality. pak ak ~an - aE omnh+ nEE - FLORSHEIM” in a shoe dis poses of all doubt about its You take nothing on faith; you know the shoe is right | or the name would not be there. Shoes $12. Some styles up to $15 THE FLORSHEIM SHOE Manufacturers The Rainbow Booklet ww em hh 0 err et ok a elo al af ah-o- O a el - eh Gh + ere et + ah + athe ai - OH ~ aa a - a ~~ - aa Oxfords $11. COMPANY Chicago Style M-55 “Styles of the Times” on request Brom. latory to you FREE Easiest riding, most comfortah le wheel Z - built. We'll ship it to you on approval A . You'll wantit sure when you see the ov 18 exclusive features of the splendid 1921 model electrically equipped BIACK BEAUTY Big color-illustrated catalog shows large et variety of styles—describes feature . NX] fully. Choose the wheel and we’lls ship express prepaid on approval with. cost. A small deposit and A DOL LAR A WEEK makes it yours, Our dire factory price saves you money—a sav- ing you cannot afford to overlook. 5 year guaranty and 6 months’ ac- cident insurance with every wher. Send now for big color- illustrated nue it’s FREE! Haverford Cycle Company Established 25 years '} Dept. 384 Philadelphia, Pa. ae Be a Black Beauty Owner Agent ) Publishes cash art as- . signments, MAGAZINE lessons and articles on Cartooning, Designing, Illus- trating, Lettering and Chalk-Talking. Criticises amateurs’ work. Full of in- formation for artists and art students. Satisfactory or money refunded. 20c a copy, $1 a year. Send $1 NOW, Thrift Stamps Taken 9 G.H. LOCKWOOD, Editor, Dept. (40, Kalamazoo, Mich, AN EASY WAY TO MAKE MONEY 2: plod along on a small salary. Be independe nt. Go in the tire re- pairing t business. One man says “‘I made $60 the first Others average $200 to $500 a month ery little capital needed. Jobs plentiful, Every oo & pos- sible customer. No experience meeded. We teach you, SHALER Tire mea Outfit Improved Wrapped Tread Method Used by Tire Manufacturers Does as good wor’ as the big high priced vulcanizing outfits. A boy ean use it. It’s the only vulcanizer that has Automatic Heat Control, and can’t undercure or overcure a ‘tire. Requires no watching or regulating. © FREE Book **How to Open a Tire Repair Shop.”” It = how to make bie money. delay. Write quick C. A. SHALER Co. 2103 Fourth St. | Waupun, Wisconsin IN POP-CORN CRISPETTES BIG MONEY Meisner, $250 in one day. Shook, $311 one day Sept. 1920. Erwins boy (going to school) . _— $35 oe hee afternoon, rwin says yields $25. — b Notheory! No a ae dey Actual proven record of successes. Send for booklet, Long Eakins Co., 447 High St., Springfield, Ohlo LOOK AROUND! EVERYBODYS USING WHITING -ADAMS BRUSHES o-round of Brushes. ie Bow gk i of kinds and sizes of WHITING-ADAMS BRUSHES .. = Your dealer sells them or will quic get them for you. Send for Illustrated Literature JOHN L. WHITING « J.J. ADAMS CO., Makers for Over Boston, U.S.A. Se Seer

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Popular Science Monthly Apri IF YOU HAVE AN | thick, which is bent to form a reflector, Dr _as shown. A piece of No. 24 copper INVENTION and DESIRE wire is soldered to the metal case of the : TO LEARN HOW TO — rere to ~ a ie B, —* TT . also O -In. snee Tass. no SECURE A PATENT, send for Our Guide Book, HOW TO sehen Aa ddtiemnell 45 Sha aueniiiie ak oi | | q tne GET A PATENT, sent Free on request. Tells our Terms, Methods, ni - . ° ° ° pas etc. Send model or sketch and description of your invention and we es . owe ° ; —_ . hia? ha ehnea will give our opinion as to its po 1 | ¥ | it) patentable nature. i ae : ol RONNIE So ox5 5 a unsaved icoeeee teenie nf Hi in) RANDOLPH & CO. t RMR ore wes sas sos Pv she Siew Rk ee ewan & C ‘ l i) 130 F St. N. W., Washington, at. ' 1, eT SPATE. cs vsckissnssacoet M f) = a i i MIRE M } thro i wires lutel breal ‘ . : . pe corn: think of a simple, practical idea | dass that will fill one rd the many re- Ihe” 1t 1S quests we have on file for new inven- Pe i ae. SS OE Se ee ee —— It may mean wp saredhy 4 you, “4 , - atone . ~ ; and housands of things are needed R1GHT Fs = san Now. Your brains can help. Send to- ahd hit day for oar erect ee . To the Man With an Idea i my paste ti n rade arks, eir yi n f lu Protection and_ Exploitation’’ Te I offer a most comprehensive, x= | c Ee but and — ag about making nt perienced, efficient service for his 4 : "4" the | mone m ideas than you ever ms i | pie = ° ae ° curiam. Bt celle MRRay of — — 3 agp and the ihe This illuminated writing-board is use- Tl things that are wanted, = development of his proposition. |; ful to meter inspectors and others who shak too. A postal will do— lie Send sketch, or model and description, ip have to make records in dark places are “rest saat ‘7 for advice as to cost, search through |}. of it i..4 prior United States patents, etc. Pre- |}? { Pea liminary advice gladly furnished with- | | or Hag out charge. \ | the battery and run to the contact cent: *G My experience and familiarity with , j : iv. various arts, frequently enable me to point C. nail PATENTS hs ne ra agg astoprobable |} § } Two paper clamps (D and E) are smal , e tent 4 ret y . . res © screwed to the board to hold the writ- pow the dollars out of their ADVERTISED fig Booklet of valuable information and form ||. |} ing-tablet. Now, when the tablet is 200 ideas—having facilities . an or properly disclosing your idea, free on ° = none others possess. For SALE FREE GB] request. Write today. | pressed down by the hand, the spring holes nS ey MN tn INVENTION And 2 RICHARD B. OWEN | B connects with the contact C, thus er W Don't delay—get the. MANUFACTURING Oa Biieneiomenn.c. | forming a circuit and flashing on the well. book at once. SUPPLEMENT 2276-D Woolworth Building, | light. ic wu ew Yor ity : ; AMERICAN F a i smal N Published for the eee ate : + ° ° : INDUSTRIES, INC. man with an idea TER SALE RAL ; SES Building a Folding Table for a Send for free sample wi 201 Patent Dept., eee One year’asub- WASHINGTON, D.C. IMM scription Sve a Balcony Garden breal SS—————————emeEeseee aa HE folding table shown in the -_ ° ° ° ° VIS I. ; ss S. Patents accompanying picture is so simple ‘a . . ) PA i I N 1 S in construction that any amateur can differ Five years ago, practically without capital, J. G. | . . ie Tuftord, Elyria, Ohio. and his associates Smith and | Make one. The top of the table is onal ean a a Ingwer started business with ithe, now well-known | made from strips of wood taken from nd Booklet i t - i. Dd >be ee - >. . . : an 7 nad erase eee foreign patents obtained through Lacey & Lacey. the side of a box, and nailed to two : Promptness Assured Best Results ‘ 5 “ x befo1 tel { limi Fourteen vot of “oy heels are now produced cross strips of 1-in. stock, 3 in. or 4 in. Dig Send drawing or model for preliminary daily. The profits already amount to many hun- = . - ° ™ ae 7 i * f Patent Ofhce records dreds of thousands of dollars and foreign patents wide, set endwise. Notches are cut in vour CARATS OF 5 ee a have been sold to the extent of $550,000.00. . and report as to patentability That demonstrates, the financial posietinins even TABLE TOP and 4 3 of an extremely simple invention of merit properly —— VADLE = All Business Given Prompt and patented. Read = : ‘ouniiies Yy they Proper Attention j=] PATENT-SENSE are in in Gate EOITION ‘~ ~ | WATSON E. COLEMAN, Patent Lawyer, | ial Che Book for antaes & Mfrs? \ 4 GROOVE ree EA yy Return Mail . Write ) 624 F St., Washington, D. C. - LACEY @ LACEY. Dept.¥-S Washi Re. . 4 / A Practical Use of the Steel Square Tf won RANG 7] | STORAGE BATTERIES SIMPLIFIED Sq {i | | By V. W. Pace Vol. I and II. By F. T. Hodgson hy I Tells how to charge, ob, Bs and oae uid storage batteries The methods of using the Steel Square to make it of the yyy ~ BRACE Poe | | Also outlines their industrial uses, including how they are most practical value to the carpenter and workman are fully / al I used in central station standby service, for starting automo covered. Illustrated with diagrams and_ explanatory Us Lome walls bile motors, and in ignition systems. 208 pp., illustrated. sketches. 600 pp., 500 illus. Price, 2 vol., $3.00 AU GROOVE ¥ SEAS Price, $2.00 i . 4 ; “a oer Science Monthly, 225 West 39th St., New York City | Popular Science Monthly, 225 West 39th St., New York City Beautify your balcony with flower-boxes fiber - 3 that rest on folding bracket-supports have Wireless Taught By Mail ne Be it SS oe | e) al. . | the cross-pieces as shown in the pic- zine, rg , be J id a ture. The square groove should fit wall; enauh Supe Ganded tation ee rer On ne ae ecivend and :. | over the top rail of the fire-escape or = l Me ( y eded for Merchant ine, Big L Jireless Stations, Railroa Ly : : - rE Sy iy ( ompanies, Commercial Concerns, Lake and Ocean Steamships. — start ms | balcony. The other groove with one = a 2 amonth plus Room and Board, which means more than $200 a month. ne o x) alle : : cer : a. our recent graduates is getting $6,000 a year. Chance to see the world slanting side rece es the supporting of f efdecate in land stations in America. a Gai . brace, which with the notch at its ot Ire A Some of our students have passe i ‘ : ° en commercial examinations in ten weeks. One student secured license in _ lower end fits over the lower horizontal 2 a ght w . Start s ri J Jins ti t home. e i | . . re oe to every student, our marvelous new automatic "Natrometer” which | rail of the balcony ° will ans 8 wi Ss) s i i nations Ta | , V c Saat ibaa t Ge tteeic ts akeues. You receive this instrument bene | | The tw 1] supports need not be now your TT -{ sy sona rty upon comp ‘ - now oe Oe aoe Oa portentty | noe to a — a ate a mei of Today.” , | but 1t is safer to nail them to preven NATIONAL RADIO INSTITUTE Dept. 527, Washington, D. C. re ale cat slipping a es Lem appli s i % 5 . 102 — > . ~~ *- us a a

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Ww west ae”) iS pros i ao Ty ic- or ne ng its tal yle, ent 1es. April, 1921 Dry Powder for Cleaning the Hands HE powder described below will be found superior to many of the “‘hand-cleaners” or ‘‘mechanic’s pastes” on the market, and is much cheaper. Washing-powder, - 2 pounds Powdered borax,- - 1 pound Yellow corn-meal, - 114 pounds Oil of sassafras or citronella, a few drops Mix thoroughly and pass_ twice through a sieve of about fourteen wires to the inch. This is not abso- jutely necessary, but is a help in breaking up the lumps. The yellow corn-meal is better than the white as it is sharper and so removes the dirt more readily. It is far superior to sand, marble-dust, etc., used in most pastes, as it does not grind the skin, but gives up some of its oil, leaving the hands much softer. The hands should be wet before shaking the powder on them or much of it will be lost. Use a shaker made for soap-powder (costing 10 or 15 cents), but enlarge the holes with a nail. In fact, a small bakinge powder can with 20 or more nail holes in the cov- er will do very well. Ifno sieve is used, put a small bolt or nut in the can as it THREADED TOP mO.tS You will serve cleanliness and will help to economy with this break up the powder and shaker lumps. If you wish to experiment, make it up in ounces instead of pounds, trying different proportions. There are sev- eral washing-powders on the market and you may have to try two or three before one just strikes your fancy. Dig your nails into the powder on your palms as you wash your hands and you will be surprised how easily they may be cleaned when your hands are dry.—ROBERT A. CHANDLER. Rejuvenating a Brick Wall with Paint IRST of all, you must get every particle of loose stuff from the walls, which may be done with a loose fiber brush; then dust off clean. If you have enough old paint to do the job, thin it down with oil and a little ben- zine, strain, and apply quite thin to the wall; brush this well into the surface, and let it have several days to become hard. The next coat should be a lead paint, of fresh material with raw oil and just enough driers to dry it well in a reasonable time; a little turpentine will also be of advantage. This will now give you a good foundation for whatever paint you may want to apply.—E. STANDIFORD. for our blank form ‘Evidence of Conception.”’ ae a a aS ee ee -TRADE-MARKS COPYRIGHT FREE OPINION AS TO SPECIAL OFFE PATENT ABLE NATURE Before disclosing an invention, the inventor should write This should be signed and witnessed and if returned to us to- gether with model or sketch and description of the inven- tion, we will give our opinion as to its patentable nature. Our Three Books Mailed Free to Inventors Our Illustrated Guide BOOK HOW TOOBTAIN A PATENT Sent FREE on Request Contains full instructions regarding Patents, Trade-Marks, Foreign Patents. Our Methods, Terms, and 100 Mechanical Move- ments illustrated and described, Articles on Patent Practice and Procedure, and Law Points for inventors. OUR TRADE MARK BOOK Shows the value and necessity of Trade-Mark Protection and gives information regarding unfair competition. OUR FOREIGN BOOK We have Direct Agencies in all Foreign Countries. Write for our illustrated Guide Book on Foreign Patents. SPECIALIZATION Our Staff The field of invention is so vast that it is impossible for any one man to become an expert in all the different classes of invention. Only those practically skilled in the class to which the invention relates are capable of rendering efficient service. For this reason Victor J. Evans & Co. employ a number of patent lawyers and mechanical experts who have been selected for their special knowledge and ability in certain lines of invention. Each case is placed in charge of experts in the classes in which the invention relates. THE VALUE OF YOUR PATENT Will depend much upon the skill and care with which your case is prosecuted in the United States Patent Office. This work will receive the benefit of skill and experi- ence acquired by a long and successful practice. We spare neither time nor pains to secure the broadest possible patents that the inventions will warrant. That every case entrusted to us receives our best efforts, and that our work is done consistently, skillfully and thoroughly is evidenced by the many unsolicited letters of commenda- tion that we receive constantly from our clients. We will furnish upon request lists of clients from any State in the Union for whom we have secured patents. Our New York, Philadelphia, Pittsburgh, Chicago, and San Francisco Offices Owing to the growth of our business we have established for the bene fit of our clients Branch Offices in New York City, Philadelphia, Pa., Pittsburgh, Pa., Chicago, III.,and San Francisco, Cal. These branch offices being located in these large commercial cities, together with our Main Office located nearthe U. S. Patent office, in Washington, enables us to more promptly handle the business of our clients, particularly as the branch offices are in constant touch with the Main Office and fully equipped to handle patent business in all its branches. Highest References—Prompt Attention—Reasonable Terms Nr Vin | ef | e i Patent Attorneys New York Offices Philadelphia Offices 1007 Woolworth Bldg. 135 S. Broad Street 514 Empire Bldg. Chicago Offices, 1114 Tacoma Bldg. San Francisco Offices, Hobart Bldg. Main Offices, 760 9th Street, Washington, D.C. aes J. EVANS & CO. i Pittsburgh Offices WIN 103 as described above. Gentlemen: Please send me FREE OF CHARGE your books | 1 |

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PATENTS F YOU HAVE AN INVENTION which you wish to patent you can write fully and freely to Munn & Co. for advice in regard to the best way of obtaining protection. Please send sketches or a model of your invention and a description of the device, explain- ing its operation.

All communications are strictly confi- dential. Our vast practice, extending over a period of seventy years, enables us in many cases to advise in regard to patentability without any expense to the client. Our Hand-Book on Patents is sent free on request. This explains — our methods, terms, etc., in regard to Patents, Trade Marks, Foreign Patents, etc. If you are a reader of SCIENTIFIC AMERICAN you are probably aware of the fact that it has a special appeal to the inventor. Each issue contains a description of a large number of recently pat- ented inventions. Pending pat- ent legislation as well as the most recent rulings of the Patent Office and the courts are considered in its columns. MUNN & CO. SOLICITORS OF PATENTS 683 Woolworth Building, New York 624 F Street, Washington, D. C. Tower Building - Chicago, IIl. Hobart Bidg., 582 Market Street, San Francisco, Calif.

0 FOR Asking No.

be the en tell rit from diamond. St EE er eS u se ie 0 8 = Se te GEM RING with all th est diamond

" ith tult "carat weight LIENITE GEM. Select the one you like best: Size must be estate’ when ordering. When your ay" EM y the mail man 08 are Inonti monthly ant I paid. ‘tion Pees a within 10 days ectly satisfied. y a ted yan Ring Today THE LIZNITE GEM COMPANY “The House of Quality and Price"’ Dept. 411 — 128 N, Wells St.,Chicago, Ill.

10c to 25c a Day Pays For the Symphonola Beautiful models in genuine Oak, Walnut, Mahogany—Hand- somely finished. Compare tone , construction, price, terms, with higher priced phono- graphs. See the saving. ; aver 2 roars Time or the autiful Period Model here shown. 18 mos —2 yrs. on other popular models. Convenient month- ly payments. Enjoy your Symphonola while Paying Plays All Records Using steel needles, as Sym- phonola, Victor, Columbia Emerson, without expensiv: extra attachments; Pathe or Edison Records with sapphire or diamond points. Records 70c Postpaid Symphonola Records play- able on any phonograph. Contain best of music. Get our latest Record list, and save money. Beautiful Book FREE Illustrates Symphonolas in natu- ral colors. Full details, prices, terms, construction. A postal quickly brings it. Get your copy s FREE. . NOW-—It’ Larkitt Cotnc. Desk SPSM-421 Buffalo, N. Y.

T NOR i AN J Ukulele, Hawaiian Guitar, Violin, Mandolin, Guitar, Cornet or Banjo Wonderful new system of teaching note music by mail, To first pupils in each locality, we give a $20 superb Violin, Mandolin, Ukulele, Guitar, Hawaiin Guitar, Cornet, Tenor Banjo or Banjo abso- lutely free. Very small charge for lessons only. We guarantee suc- cess or no charge. Complete outfit free. Write now. No obligation. SLINGEBLAND SCHOOL OF MUSIC, Ine. Oept. 603 CHICAGO, ILL. WILLIAM C. LINTON Consulting Engineer and Patent Attorney ‘Inventor's Adviser’’ Mailed free on

request. Gives full information as to Patents, Trade Marks and Their Cost OFFICES 364 University St., 431 etteont Union Bldg., Montreal, Canada. Washington, D. C. i |store) onPATENTS ontains valuable information and advice to inventors on securing Patents. Send model or sketch of your invention for Free Opinion of its patentable nature. Prompt service. 20 years experience. Write today. TALBERT & TALBERT 4911 TALBERT BLDG., Washington,D.C. 2, Learn to Dance YoucanlearnFox-Trot,One-Step, Two- Step, Waltz and latest ‘ ‘up-to-the-minute’’ so- ciety dances in your own home by the wonderful Peak System of Mail Instruction. New Diagram Method. Easily learned; no music needed; thousands taught successfully; success absolutely guaranteed. Write for S jal Terms, Send today for FREE information and surprisingly at offer. ae onane. ee PEAK, 7 Broadway, a. i. PATENTS Secured Prompt Service. Avoid dangerous delays. Send for our “Record of Invention” form and Free Book telling How to Obtain a Patent. Send sketch or model for examina- tion. Preliminary advice without charge. Highest references. Write TODAY. J. L. Jackson & Co., 122 Ouray Bldg., Washington, D. C.

April follov 1 in. iengt ne, fe in. valeo of 6-i t in. poarc inelir stock hinge ft. by Te uprig the 1 the | the ° and in pl. insid three place Th faste with Ma U bins dust

com mea pow If of t thro that cons thre witk dou like briq ina conl The bear piee £Oo

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ful Ree

April, 1921 following materials: One 16-ft. board, 1 in. by 4 in., to be cut in 3 ft. by 8 in. jengths; two 12-in. strips, 1 in. by 2 n., for the frame. Two 12-ft. boards, in. by 6 in., to be cut for flooring, aleony, and shelves. Six 12-ft. strips of 6-in. lap siding. Five 12-ft. strips, i in. by 1 in., for roofing. One 12-ft. board, 12 in. by 1 in., for rafters and incline, and several short pieces of 1-in. stock for the upper siding, two or three hinges and screws, prepared roofing 4 ft. by 4 ft., paint, and nails. To a frame made up of 4 in. by 2 in. uprights and 2 in. by 1 in. crosspieces, the upper siding or frieze containing the baleony window, is nailed. Then the two flooring boards, at the top and side of the incline, are fastened in place. To these the incline with its inside wall is hung. With the first three boards of the lower siding in place, ledges for the shelf are put in. The roof, made up of 4 in. by 1 in. fastened to curved rafters, is covered with canvas or prepared roofing. Make Your Own Briquettes to Save Coal SERS of coal invariably aceumu- late at the bottom of their coal- bins a considerable quantity of coal- dust mixed with small particles of coal

From coaldust, sawdust, and a suit- able binder you can easily make briquettes that give fully as much heat as coal chipped off from the larger pieces. This mass is too fine to be used in the furnace or stove, as it will drop through the grate and, unburned, be- come mixed with the ashes. This means a complete loss of the heating power represented by this coaldust. x, If you have a considerable quantity of this fine coal in your bin, do not throw it away, but make briquettes that can be used in the furnace with a considerable saving of coal. Mix three parts of the coaldust thoroughly with one part of sawdust, and make a dough or paste by using some binder, like glue, asphalt, or tar. Make the briquettes by molding the plastic mass in a small flower-pot and allowing the conical briquettes to dry in the air. They soon become hard enough to bear handling without breaking to pieces. When burning, they give out good heat and burn a long time.

to You $1.75 anhr. Auto Expert $40-$50 a Wk. Chauffeur $200 a Mo. Domonstrator i $225 a Mo. - Tire Expert $4,000 a Yr. - Salesman $5,000 a Yr, Garage Mgr. $10,000 a Yr. Gar. Owner and Tractor Business Don’t stay a Low-pay man wishing for a good, steady income to come through lucky breaks. Make your own luck. Take a short cut to top pay right now. Come to the world-famous Rahe Auto & Tractor School. In 6 to 8 weeks Henry Rahe will fit you to pick your job in the Automotive Business—the one business that needs more men than ever and pays the biggest money. Remember, it’s the Rahe *. School Tractor & Flying 2 Million Dollars Invested—Nearly 40,000 Graduates Learn Here Easily and Quickly and learn Right. You work daily doing real jobs under Master Instructors on all types and models of real Automobiles, Trucks, Tractors and Aviation Equip- ment. You learn by the Rahe Practical Job Method of Training—-the same metnod of training that has brought // success and independence to nearly 40,000 Rahe Trained Men in every section of the country. You need no previous experience; no special schooling. Best of Living Conditions. Board and room always reason- able, Plenty of opportunity to earn part living expenses while here.

More Get my fine 84-page Catalog and Special Catalog Free Tuition Offer ‘Salere you go to any Calls school or shop. Both are free. Address school nearest you, for Rahe HENRY J. RAHE, Dept. 2882 Trained Kansas City, Mo. Cincinnati, Ohio Men Than & Can Supply!

orld’sBest +, Roofing at Factory » VS

Las CARPENTERS, Shipfitters, Bricklayers, Structural, Concrete and Sheet Metal Workers, Electricians, Mechanics, Plumb- ers, Pipefitters, Boilermakers and others can earn more money if they know how to read Blue Prints. By oursimple method,we train youina | shorttime. Writefor Catalog B, stating trade. | | |

“Reo” Cluster Metal Shingles, V-Crimp, Corru- gated pending Seem Painted or Galvanized Roof- ings, Sidings, allboard, Paints, ete., direct to you at Rock-Bottom Factory Prices. Positively greatest offer ever made, Edwards ‘‘Reo” Metal Shingles cost less; outlast three ordinary roofs. No paintin orrepairs. Guaranteed rot, fire, rust, lightning proof. weces Free Roofing Book aoe WW a eves Get our wonderfully low prices apd free samples. We sell direct to you and save you all in-between dealer's protts. Ask for Book a, 198 _—<£ BE A DRAFTSMAN Earn $35-$150 Week Draftsmen are in demand. Books and tools FREE. Write for Catalog G. DOIT TODAYI Columbia Correspondence School £19 Carroll Dept. Drexel Bidg., Phila, Pa. | BEATS 15c GASOLINE | Starts Car Easy in Cold Weather Amazing auto invention. Wonderful new carburetor. Guaranteed to re- duce gasoline bills from one-half to one-third and increase power of any motor from 30 to 60 per cent. Sent on 30 DAYS’ TRIAL Fits any make of car. Put on ina few minutes. Fords make as high as 40

RICED GARAGES quai FR ‘Samples & | ‘Roofing Book 45 Master Keysk The most wonderful and only sct fof keys of its kind. They open and test thousands of different'locks. They ee ow P Lowest prices on Ready-Made Fire-Proof Steel Garages. Set upany place. Send postal for ge Book, showing styles.

JHE EDWARDS MFG. Co., 448-498 Pike St., Cincinnati, 0.

miles to a gallon of gasoline. Other cars show ropor- have satisfied thousands of purchasers, and are used tionate increase. Take advantage of our special 30-day and recommended bv locksmiths, janitors,detectives,and J other great key users. They are unequaled as auseful, convenient, and household article. 3end $1.00 for set and novel key chain. MASTER KEY CoO 36 Manhattan on * MILWAUKEE, WI Sscaeniemeeteeieniaiaantitiiatetemereteamemne AIR FRICTION CARBURETOR Co. (333 Madison Street Dayton, Ohio

trial offer. Name your car. AGENTS WANTED. |

Ask for ree ~ Free Catalog Catalog NIG Protect your tools from rust, knocks, bangs and theft in abso- lutely the best tool chests made for Machinists. Tool-makers, Carpenters, Auto Mechanics, Electricians and Household Use. Write for prices and ‘‘Satisfaction-or-money-back” guarantee. UNION TOOL CHEST CO., Inc., 24 Mill St., Rochester, N. Y.

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There! That’s fixed Think of the times you have needed a Sargent Plane. When the dresser drawer stuck, or little Willie’s coaster developed splinters, cr you wanted to put a proper finish on that shelf you built. Ask your hardware dealer to show you the Sargent Auto-Set Bench Plane. Have him dem- onstrate the exclusive Auto-Set feature which enables the blade to be removed, whetted and re- placed in exactly the same po- sition without re-adjustment. The Sargent Book of Planes will be sent free on request. SARGENT & COMPANY Hardware Manufacturers 50 Water St., New Haven, Conn.

Get into BUSINESS iar Yourself Own a Tire Service Station The man of big business today, once started for himself in a small way. The Adams-Barre System of Vul- canizing makes repairs that are

im possible by ot her methods. Recon- structs tires other systems reject. Guarantees all repair work for the life of the tire.

Satishes the customer 4 and makes more profit A for repair man _ than 4 possible by any other method. Investigate, and you will buy no other Vulcanizer. Free course of instruc- tions with every equipment. Any one can Jearn our system. Everything for the tire repair man. Write for catalog. THE ADAMS-BARRE CO., 1244 High St., Columbus, Ohio Pilliod TOOL CASES EXCEL Machinists, Tool Makers and Carpenters find them most tatisfactory in construction, appearance, service and price. Immediate shipment. Booklet describing 20 styles on request. The Pilliod Lumber Co. Dept. A, Swanton, Ohio

A Simple and Automatic Candle-Extinguisher SIMPLE arrangement by means of which a candle may be made to extinguish itself within a given time is shown in the illustration. A support of stout wire is twisted around the candle; this is bent in a semicircle a little more than halfway up and it finally ends in aloop. The bottom half of a small can is cut to act as the extin- guisher. A / piece of thin twine is push- ed through the center of the can and tied with a knot. The thread is carried over the hook in the support

— TIN CAN 3 j instruction purposes; Automobile Man- Bee i ufacturers, Makers of Small Tools (who :: require work of minute accuracy), | Machine Shops large and small, many other industries, even hotels and de- partment stores, are using Monarch Lathes with universal satisfaction. Monarch Lathes are built with all the | . latest improvementsand many exclusive |, i 44 features, in many sizes to meet all lathe} eee | work requirements-—the small shop : handling only light work, orthe largest Pp : shop or plant where the heaviest work a is done. : mad Monarch Lathes are reasonably priced i within the reach of every prospective purchaser. Write today for catalog and price list.

Schools write for cur special school proposition The Monarch Machine Tool Co. 108 Oak Street Sidney Ohio

ACCURATE Ask your dealer. ~ Ask us for Catalog No. 12 THE [UFKIN PpULe (0, S44". ASBESTOS | We are miners and shippers of Crude Asbestos in any quantity. We produce all grades at our world famous BELL ASBESTOS MINES, in Canada. We also card fibres, spin yarns, weave cloths, and make all sorts of Asbestos products. For anything you want in Asbestos, turn to KEASBEY & MATTISON COMPANY Dept. S-4. AMBLER, PENNA., U. S. A. : Owners of the world’s largest Asbestos Mines i MOTORS LARGE pace pone NEW WASHING MACHINE MOTORS of ver ee = ey Ke a I I fac mony y guarante able for 0 one ati LIT oltee. ar mri “Bo ttle Was aan, Air Compressors, G am Sep Seva all ba thes. Et (Mail $5.00 cash or Money order = We will send C0 D. sub ject to full examination. | Generat: 75 ee et ee eatages Special Quantity Priece Vales $98.50

MANUFACTURER S DISTRIBUTER ous H. JOHNSTON. Boxazg W. E,, Pittsburgh, Pa. ‘BO WLEGSandKNOCK-KNEES" UNSIGHTLY SEND FOR BOOKLET SHOWING PHOTOS OF MEN WITH AND WITHOUT The Perfect Leg Forms 3 PERFECT SALES CO. ,140 W. Mayfield Ave., Dept. 45, Chicago, lll.

ee ee ee ee ee ee) a

RMR EH RO TP OS aM nN penance rca I STAR HSNO MUONS

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a SES ll April, 1921 Nevde HAND ROG TALLY Counts by pressing thumb-lever Used for counting anything from number of persons attending a public place, to the number of pack- ages inan-inventory! Registers up to 10,000, then repeats, and can be set back to zero from any figure by one turn of knob projectingon right. Finger ring so located as to permit of use in either hand. The Hand Tally is particularly handy for gatemen, trafic officers, steamboat and other inspectors; for telephone and electric companies as a pole counter; for nurseries and foresters as a tree counter. Use- ful, too, in mines, lumber camps, ranches—man more places you can think of. Price, $5.00. Ask for catalogue showing production counters, speed counters and others. The Veeder Mfg. Co. 44 Sargeant St., Hartford, Conn. THE NEW METAL WORKER PATTERN BOOK. By G. W. KirrrepGe anv Associates. The most complete book on metal pattern work published. It contains 259 problems, including 65 on triangulation. 544 pp., 900 figs. Price $7.50 Popular Science Monthly, 255 W. 39th St., New York ENGINE CES. SSss)/ On Skids, Ready to Use. From Pittsburgh §5 More Big Cut On All Sizes Up to 30 H-P. NOW, of all times, is the time to buy your engine—while my prices are cut to the limit, and while you can get quick shipment. Surely you can use engine power at.these prices to cut your own labor cost and keep on making money. I sell on 90 Day Test--Lifetime Guarantee Remember this is my 36th year in the engine business. You take no chances—You buy direct—Cash or EasyTerms if arranged for. Latest Catalog, Price List, and all infor- mation FREE, ED. H. WITTE, Pres, Witte ENGINE Works 2225 Oakland Ave. Kansas City,Mo. 2225 Empire Bldg. Pittsburgh, Pa. Decorate the Whisk-Broom Holder with Fretwork NEAT whisk-broom holder can be made from 1%4-in. material. A discarded wooden bedstead would furnish ample material for its con- struction. Cut a piece 8 in. by 12 in. and carefully mark the design you intend to follow. Place it in a vise and saw out the pattern you have drawn, jg —__ All Mie} i} ag l} [ROUND riEAD | BRASS SCREWS Vy in A suggestion for a whisk-broom holder. With a fret-saw you can cut the design in less than one hour being careful to cut a hair’s breadth outside the lines. Rub this small margin off with sandpaper, to the line. The edges will then be _ perfectly smooth. The brackets used are 1 in wide at the center and !¢ in. wide at the ends. Their length is 4 in. and their thickness 15 in. Fasten them to the wall piece by means of four round- headed, brass screws. The face piece is 2 in. by 4 in. It is also screwed in place. Bore a hole for each screw before inserting it. As to finish, white enamel would be best if old lumber is used, while stain and varnish could be used on new stuff. It Is Easy to Construct an Indoor Miniature Hothouse F great interest to the indoor gar- dener is the miniature hothouse. In this it is possible to keep on growing plants throughout the winter. By fol- lowing the plan indicated, there is no need to have any bother with lamps or fire. In the first place a large wooden box should be secured. This might meas- ure about 3 ft. square or any suitable size. It is now needful to get an oil- or paint-can, or anything of a similar nature. This should be of such a size that it will fit in the box when it is lying down. Get a quantity of saw- dust or sand and place a layer of this a few inches deep on the bottom of the box. Now put the can on this and bore a hole in the side of the box just large enough to take the mouth of the can. Before finally settling the can into position, it is not a bad idea to paint it inside and out to prevent rust. The inside painting is accomplished 107 Williams’ Superior Drop-Forgings To Order N the building of Machine-tools, Tractors, ‘Trucks, Automobiles, Williams’ Su- perior Drop-Forgings have played an Airplanes, etc., etc., important part. Excellence of material, craftsmanship, engineering skill and equipment, plus the inflexible Williams principle of measuring their product by the su- perior standard set up by the founder of the company nearly half a century have resulted in a ago, constant growth of the business. Four great plants are now maintained in widely separated localities, thus facilitating delivery and assuring customers of close and efficient cooperation. Williams’ stock Superior Drop-Forgings standard lines of and Drop- Forged Tools are fully described in the following books, any of which will be sent on request: Wrenches Wrench Sets Machinists’ Tools Lathe Dogs Clamps Caliper Gauges Tool Holders Pipe Wrenches and Vises Eye Bolts Hoist Hooks Wire Rope Sockets J.H. WILLIAMS & CO. “The Drop-Forging People’’ CHICAGO 1007 W. 120TH Sr. BROOKLYN 7 RICHARDS St. BUFFALO 7 VULCAN ST. ST. CATHARINES, ONT., CANADA

Page 90

4 Here is a plier that gets into tight places where the ordinary plier can- not reach. The extra thin nose of the \Ried Dewil/ eer i,c pat ogee

Combination Thin Nose Plier No. 1024 makes it almost indispensable for every mechanic. The slip joint in- creases its usefulness—the jaws can get a big bite as well as a small one on nuts or pipes. Has sheer cutter, also. Forged from high grade tool steel, with ‘“‘no pinch” scientifically shaped handles, Dentyne Knurled. Fully nickel plated. At your dealer’s, or from us. Sample $1.10 for 614-inch size. Red Devil’ TRADE MARK. Chain Nose Cutting Pliers No. 654 A long nose side-cutting plier for getting into cor- ners or working on small jobs. Forged from high- grade tool steel. ‘‘No pinch”, Dentyne Knurled handles. Length 6 inch. At your dealer’s or from us $1.65 each.

Red Devil Pliers No. 654 Red Devil Glass Cutters No. 024 Guaranteed to cut more glass at less pressure than any other cutter. The . cutting wheel is hand-made and hand- honed. The handle has a finger-rest grip. At your dealer’s or from us 20c each. Tool Booklet on Request Smith & Hemenway Co., Inc. 264 Broadway New York The Red Devil brand covers a complete line of hand tools for mechanic, electrician and motorist. The Red Devil Line is known the Glass world over wherever tools are used. Pliers, Cutters Chain Drills, Auger Bits, Chisels, Punches, No 024 Wrench Sets, Lock Washers with six-point contact, etc.

2136

by pouring a little paint into the can and turning it about until the interior is well coated. Settle the can into place on the sand or sawdust, and then proceed to bury it with the material. Go on putting in the stuff until the box is about half full. Then put a number of strips of wood running both ways across the top of the material. These should be cut so that they fit tightly inside the box. <A sheet of glass and a close Wy fitting stopper ¥ for the can com- plete the minia- ture hothouse. The model hot- house is worked in this way. Turn the box up on its side and then fill the can with boiling water. Put in the stopper and let the box down again. The plants to be grown are then placed on the strips of wood. The sand or sawdust should be kept in a moist state. It will be found that the can will continue to radiate sufficient heat for at least twenty-four hours. Thus the only thing needful is to empty and re-fill the can once a day. It is not much trouble to take out the plants and return them again to their place. —S. LEONARD BASTIN. ~

The hothouse is heated by a can of hot water covered with sand How Boiler Cracks Can Be Checked HEN circumferential or longi- tudinal cracks develop in the , shell of a boiler, the usual method is to | apply a patch giving the proper factor of safety and consider the job finished. It has been found in some cases that @ ¢ . © 6 ¢ \e © o & wt 6 o& © @ 6 6 6 © © Before you put a patch over the crack in the boiler shell, drill small holes at the end of the crack to prevent it from extending

' ' : 4 ZS ~

the expansion and contraction of the shell causes the crack to keep develop- ing. In order to overcome this, a small hole about *¢ in. or 7/16 in. diameter should be drilled at each end of the crack. The circumferential surface tends to overcome the development of the crack to a greater Jength. It serves the same purpose as a fillet placed in the corner of machine parts to prevent cracks from developing. Popular Science Monthly

Electricians’ Knife and Tweezers We can meet dealers’ demands at once and offer attractive quantity prices Write for description MATHIAS KLEIN & SONS, Mfrs. CANAL STA. 3, CHICAGO

BE YOUR — BOSS. MAKE | MORE MONEY With little capital, you can establish a business in your own home town and make $10 to $80 per day with Anderson's Steam Vulcanizers. Better work, less cost and bigger pro’ There are Anderson schools in states, one is near you, Better schooling plus finest equipment makes Anderson tizeclogiats successful, We teach you the famous An- derson method of ye gs and the operation of derson Super-Heated Steam Vuleanizer ond Retreader. Takes 5 to 10 days in schoo! and costs . If at any time zer, we refund your $85 and Pay you $5 per day for each of the 10 schoo! days, because we sell the work you do, We will tell you now to make money. Write today. ANDERSON STEAM VULCANIZER CO. 101 Williams Bldg. Indianapolis, Ind.

Dtivered toyou Free, ‘or 30 daystrial on approval. Your choice of 44 Styles, colors and sizes of famous Ranger Bicycles, Factory- ; to-Rider lets you bay at wholesale MR prices, fonths 3toPs direct from maker. Pay ‘<‘s you enjoy 12Mon . fe Ranger of once. | “yo boys and girls easily B/N save the monthly payments. The Ranger my a 4 mrcyete than you can buy ee at ee a 4 , 4 orn s. ~ eels, $ an ires oqulpment at half sar «pre barony SEND NO MONEY. Simply write for our big, illus- trated free Ranger catalog with e Mead 22. Sempapy kal $4 or $5 wit sty A Standard, Guaranteed

BIESEEE Ds With Every Modern Writing Convenience as Write Today For Illustrated Circular Explaining Try-Before-You-Buy Plan SMITH TYPEWRITER SALES Co. (Harry A. Smith) 306 —218 No, Wells St.,Chicago, Il. BUCHSTEIN’S FIBRE LIMB soothing to your stump strong, cool, neat, light. Easy payments.

7 Braces for all Guaranteed 5 Years t-te Send for Catalog Today. ies P. BUCHSTEIN CO., 113 6th St., S., MINNEAPOLIS, MINN. Z——=. Build This Phonograph Y ourseli TREMENDOUS SAVING IN COST Easy foscinotin work, with our SIMPLIFIED PLANS. Tarsich” blue ints, s,

strument at e-quarter ther AGENTS MAKE MONEY ate, 9 pone ight

these lngirements., Wri ull details and our F FFER. elven MODERN ‘PHONOGRAPH SUPPLY co. 532 Springer Su 313 So. Clinton St.

Ma hicaco, WL.

Tee

A pril, Cc U pipe log; plun out ¢ I ha and snov iph com biey the thro rag funn over

place’ of t dow! hanc the expe pipe Ge F ir to re orde proe cyar curil boili nate dow it wi nate pree first W mor Eva tion add degr a pr this be | resp fine was} awa) HAU:

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————— ~ | i s inches. Send for printed mat- | a | ter. We also manufacture TEN 1 4 other sizes, hand operated to | eo bend from 1-8 to 6 inches 2 ina <=) American Pipe Bending SF Machine Co.

51 Pearl Street, BOSTON, Mass.. U. S. A. Manufact urers

LEARN AUTOS AND TRACTORS Wonderful opportunities constant- ly offered trained men; we train you thoroughly tostart your own business or make good money as motor expert, driver, shop fore- man, etc. 5000 graduates making good. Catalog Free. Cleveland Automobile School, 1821 E. 24th St., Cleveland, Ohio.

= AS%ent J We want one exclusive repre- sentative in each locality to use y and sell the new Mellinger Extra-Ply, Sy hand made tires. Guaraatee Bond for 44, 8000 Miles. (No seconds). Shipped _pre- Vy) aid on approval. Sample sections furnished. Donot uy until you getour Special Direct tang Bo rite MELLINGER TIRE & RUBBER ° BS 1004 Oak St., Kansas City, Mo.

How to Run a Lathe An 80 page book For 10¢ Postpaid Coin or Stamps

” 1 South Bend Lathe ,

South Bend Lathes For the Machine and Repair Shop Reduced Prices 9” x 3’ Lathe - - - 11” x 4’ Lathe - - 1S x= 5 Lathe - -< 15” x 6’ Lathe - - price $220.00 price $285.00 price $380.00 price $470.00 16” x 8’ Lathe - - = price $565.00 South Bend Lathes are made in eight sizes, 9 in. to 24 in. swing inclusive. In length, from 2 % ft. to 16ft, Send for FREE CATALOG South Bend Lathe Works, 433 E. Madison St. Established 1906 South Bend, Ind.

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Popular Science Monthly Apri | Expanding Lap Diminishes’ ~ | : ps i A Guaranteed Purchase Shop Costs : =I! THE next time you visit your hardware HE renewal of cast-iron laps in a l a machine-shop will be required far opin merchant for : , /piny _ less often when an expanding type is proc Wrought Steel Hardware used. The type shown in the illustra- abou C t — tion will save at least three fourths of brass or Carpenters fools the number required. In making them Wen you will be assured of a satisfactory pur- in.O chase if you mention the name STANLEY. PIN ing, | ADJUSTING NUT \ 4 Get ready to replace the old screen hardware with MANDREL new. Don’t hesitate about building the new OR garage: build it and swing the doorson STANLEY | | y/ pulle all Bearing Garage Hinges. SAW SLOTS in. p All of the products illustrated bear the guarantee | ya y To of a three-guarter century reputation of depend- | NX macl able manufacture. | sheet Our advertising department will send a i} | | by separate catalog of each, or one of both } i} lay lines, of our products; ask for No. 7D. \\; | acro' i | exac’ THE STANLEY WORKS i) each Main offices and plant: ASSEMBLY A SAW SLOTS F rn NEW BRITAIN, CONN. —— mys : . NewYork Chicago San Francisco Expanding laps of this type are an i | *cnennee Branch offices: Los Angeles Seatele Atlanta economy in all metal-working shops show because they do not wear out quickly on es Tesertee Si the only additional expense is caused hole. —— by the longitudinal cuts for expansion. side marowaRre The parts involved in this type are and. _ the same in number as in anv cast-iron 74 3 | lap—the arbor or mandrel, the nut for Ben¢ securing, and the body of the lap. Sold In the details shown, a tapering in eg mandrel is used. This is fitted into a Ci : corresponding tapering hole in the 18 ir body of the lap. With the lengthwise s and | cuts made in the lap and alternately Sold - ~ aie sawed from opposite ends, considerable tube expansion is obtained by screwing the : angle | nut up as is required to compensate for wear. A small drive-fit dowel-pin ! Th holds the lap body from turning on the ey Appeal to | mandrel when the adjusting nut is Your Better Judgment | turned down.-—G. A. LUERS. I | —that is the reason that the shov mechanical world unanimously How to Find the Angle of a spec agrees that good workmen and a ce Brown & Sharpe Machinists’ Tapered Key drille Tools are always in demand. | ANY times it becomes necessary of he These tools need no introduction, : | to make a new key to take the alon; for machinists have known them for place of one that has become worn or TI over eighty years. If you haven't : ees our catalog 28, why, send for it. | defective through use. 4 scre\ It should be in every kit. The If the key, as frequently is the case, drille ny pt 4 As is intended for a tapered keyway, it holes liable reference book. qui ¥ juire May we send a copy? Ct on Brown & Sharpe Mfg. Co. Ok a a OO i Providence, R. I. & Cj nN K . ~ the vy locat hole hole, | hweeD Ty The hinged gage will enable you to ae ti measure the angle of a tapered key erly | with accuracy and speed tight ,. or el: "i |= | becomes necessary to ascertain the If , -— ! . . . | angle of its taper. This can easily be be dy | done by using a template gage in the clam | manner shown in the illustration; the jig 2 | gage is inserted in the keyway and the three | angle of the taper is ascertained by the ¢ | taking the smallest and largest meas- eleva : ‘ | urements.—J. R. MINTER. Fi 110 Ponular Science Month),

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t — o> 1 =] 3 April, 1921 Make a Water-Driven Machine to Develop Photographs By H. A. Beachboard F you want to make an efficient and economical machine for devel- oping and washing photographs, first procure a quantity of sheet brass ibout 1/16 in. thick, 13 in. of \4-in. brass rod, also 18 ft 6 in. of Yin. brass rod, 6in. 4- in. O.D. brass tub- ing, 12in. 34-in.O. dotted lines 14 in. from edges. Solder this in the tank as shown in Fig. 1. The 8-in. arm covering the water-wheel is to be soldered tight later on, See that all seams are water tight. Paint the interior with D. brass tubing, one 4-in. grooved pulley, and one 2- acid-proof varnish _—s and put away to in. pulley. To construct the machine take a hi J p222222-9 dry. i Now lay out twocircular pieces 6 in. in diameter , bk-st e sheet of brass2314 | ie by 41 in. and lay out two lines across the brass FIG.4 Water-power drives this developing and washing machine and causes the film spool to rotate in the developer or and two 14 in. in diameter. Drill a Yy-in. hole through the cen- exactly 9 in. from each end, also two lines lengthwise 9 in. from each edge. Cut out with tinner’s snips the 8 in. by 9 in. piece of meta] at each corner, as shown at A, Fig. 2. This leaves in. on each side of end piece for soldering. Six in. from each end drill a 34-in. hole. Drill two 9/32 in. holes in each side piece, two at points 4 in. from end, and 31% in. from top, also two at points 714 in. from end and 1!4¢ in. from top. Bend on dotted lines and _ solder. Solder in a 34-in. brass tube 4 in. long in each end. Cut a piece of the metal 6°¢ in. by 18 in., as in B, Fig. 2. In the center and 314 in. from end, drill a *4-in. hole. Solder a’ 2-in. length of %4-in. brass tube in this hole. Bend to a right angle on the heavy line and on the washing water ter of each. The two large disks may be cut out like Fig. 3 A, leaving a rim 1 in. wide. Lay out a circle 13% in. in diameter on the large disks. On these lines solder 42 brass rods 14 by 55 in. 1 in. apart. Cut four pieces of metal 5% in. by 6 in., bend in center to an angle of 45 degrees. These are soldered in place between the two 6-in. disks, care being taken to get the edges spaced equidis- tant around the circumference, form- ing 8 pockets in the water-wheel. Place the wheels in the tank, using the two 14-in. by 6\%-in. rods as shafts to which the wheels are soldered. See that 34 in. of each shaft extends in front through the bearings to which the two pulleys are attached. Drill a 144-in. hole and solder in the 15-in. tube in the exact center 2 in. from the edge. Then solder the cover on the tank. Figure 1 shows a cover over the film reel. This is not neces- sary. Connect the two pulleys F and G. For developing, fasten the film to the reel E with pins. Close the outlets L and C with rubber stoppers and pour in enough developer to fill the tank A to a depth of 3 in. Connect the intake 7 with the water-faucet by the rubber tube J. See that the outlet K is open, then turn on the water. For fixing, the procedure is the same. In washing, close the outlet K, open L and C, and the-water serves the double purpose of driving the motor and washing the films. i Sy! Soe ; ] BRASS ROD / BRASS ROD 19) ot A ty b—__ 54 -! FIG. 2 FIG 5 Details of construction and dimensions for a developing and washing machine Suggestions of Simple Jigs for Special Work HOUGH not intended for preci- sion or repetition work, the jigs shown in the illustrations are useful for special work where a number of holes a certain distance apart have to be drilled. In Fig. 1, for instance, a series of holes equally spaced are to be drilled along the edge of a plate. The jig consists of two plates screwed together with two holes drilled; locating bushings or plain holes may be used according to re- quirements. A locating pin is made to fit snugly into the holes. To use the jig, it is clamped against the work and the first hole drilled; the locating pin inserted and the second hole drilled; the jig moved along one hole, the pin inserted again, and so on. Two alining screws are shown, which at times might be of assistance in prop- erly lining up the jig. They should fit tightly into the holes tapped for them or else be provided with locknuts. If a very large number of holes is to be drilled along the edge of the plate, a clamp might be provided to hold the jig against the work after the first three holes are drilled, as suggested by the dotted lines of the plan view and elevation of Fig. 1. Figure 2 shows the same type of jig Popular Science Monthly By H. H. Parker gq LOCATING / PIN 7 _ : ee ee | SIG PLATE é ————— WORK | @ e Ss ct —— Ga. di--~----! eae m4 pet, a ie aR. SCREW SUGGCSTION FOR CLAMP Special jigs are extremely useful for certain work, like drilling equidistant holes along straight or curved edges. This jig is for straight-edge work LOCATION ‘ — SCRATCHES » © JIG BLADE- + . cae WORK FIG. 3 FIG. 4 FIG.2. For spacing drill holes along the edge of a disk, the form of jig shown is used 111 applied to a curved edge; here the two alining screws are necessary. Figure 3 illustrates a pivoted jig for drilling holes around the edge of a disk, the points being first spaced off as accurately as possible with the divid- ers. The scratch marks are not at the locations of the actual holes as drilled, but serve to locate the jig, which is provided with a_ knife-edge angle- plate screwed to one edge as shown. This knife edge is brought carefully to the intersecting scratches, the jig clamped, the hole drilled, and then the jig is moved along to the next set of scratch marks and the process re- peated. This will generally result in a more accurate job than drilling out a series of center punch marks, for it is very difficult to drill exactly into the center of a small punch mark, but if the jig is set exactly at the mark and there is no play between the drill and the hole in the jig, or in the pivot hole, the hole must go through in pretty nearly the correct location. The writer, who has had consider- able shop experience, has found these jigs extremely useful in a variety of operations and strongly recommends their use.

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Popular Science Monthly A Grinding Attachment for a Small Lathe F the many small attachments that I have contrived for my lathe perhaps there is none that has given me more satisfaction than a grinding- head I made, to fit the slide-rest of my lathe. It consists of a piece of hexagonal brass rod about 1 in. in diameter and 2in. long. This was drilled for 14 in. clear through.» A cone was bored on each end, recessed | in. from the ends, at an included angle of 90 degrees or 45 degrees from center line. I used a center drill and countersink combined and drilled both ends of the hexagonal brass rod in the lathe. Then the 14-in. hole was drilled clear through. About midway in the rod a recess about 14 in. deep and \% in. wide was bored to form an oil-chamber. The ends (outside surface) were turned down until a perfect cylinder was formed. I then procured some 11,-in. steel rod and made 2 cones, each with a sleeve to fit over the cylindrical! ends of the hexagonal rod. These cones must be made very carefully. Next I pro- cured six steel rods 14 in. in diameter. Both ends were threaded and 2 in. of unthreaded portion left as a bearing. One cone was threaded on and a hole bored through it for a pin to lock it to the shaft. The pin must be placed sufficiently far from the end, so as to leave space for 2 lead washers, a flange lg in. thick, made of iron, the same diameter as the cone, and a lock-nut or preferably 2 lock-nuts. It was necessary to mount the bear- ing on the slide-rest and find its height, so that the center of the shaft coin- cided with the center of the lathe. Next I made a piece of metal strap so shaped that, when it was fastened to By Arthman Capron the top of the slide-rest by means of the T-slot, the bearing was in aline- ment with the centers. It is best to make this strap the same width as the bearing, minus the width of the flanges on the cones. The bearing can then be fastened to the strap by screws. A hole was drilled and tapped for a grease-cup, to reach the oil-chamber from above the’strap. The other cone was then fastened on by tapping, to fit } LL CONNECT WITH FLEXIBLE SHAFT FLANGE. FS: TO SLIDE REST The grinding attachment is fastened to the slide-rest of the lathe and is driven by a flexible shaft the shaft and a lock-nut was screwed home. The end of the shafting was then cut until only !% in. protruded from the lock-nut. The next problem was the flexible shaft to drive this attachment. I made a small brass ferule, threaded inter- nally the same as the shaft, and got some closely coiled door-springs (such as are used to keep screen-doors shut). One end was tinned !4 in., sweated into the end of the ferule and the center filled with a piece of round lamp- wick soaked in a mixture of oil and graphite. This was attached to another piece until the proper length was obtained to attach to the source of power. Then some flexible metal gas-tubing was obtained, long enough to go over the whole flexible shaft. Clamps were fixed at the ends, one for the bearing and the other for the source of power. This was filled with oil and graphite and the shaft was then threaded through. The end of flexible shaft was sweated to a piece of brass rod and a tube to fit over this rod was fastened to the end of the gas tubing. This kept the grease from leaking out and gave a good ap- pearance to the job. The shaft should run at quite a high speed, at least 1500 r. p.m. In my case it is driven by my induction motor, through an extension on the shaft, the lathe being operated through a reduction gear. The proper speed for the lathe would depend on the size of the article being surfaced. In any case, the grinder should run in the opposite direction to the lathe, and the work in the lathe should revolve rather slowly. It will be noticed that the tendency of the oil in the bearing to fly off against the work has been overcome by making a sleeve on the cone to work outside the bearing. In my case it gives entire satisfac- tion, especially on such jobs as shaft- ings or cylinders, pistons, ete. Witha medium carborundum wheel at a high speed, a polished surface is obtained directly from the first cut and the work can be guaranteed accurate, but great care must be used in feeding the wheel against the work, as there is no spring in a grinding-tool. Designing on Asphalt-Covered Glass A old idea expressed in a new way is incorporated in the accom- panying pictures. In its essential de- tails it consists of an asphalt-covered glass plate and a photograph. Any glass plate of convenient size can be taken and, after thoroughly cleaning to remove all dirt and dust, Amateurs are here shown a new way for giving expression to their artistic ability for decorative work one side is carefully covered with a rather thick layer of asphaltum. To do this successfully, hold the plate in the left hand with thumb and fore- finger, pour a sma!! quantity of liquid asphaltum on the plate and gently dip it from side to side. Continue to add asphaltum until the entire plate is evenly covered. Now lay it on a level surface. If some asphaltum runs over the edges, leave it until dry, when it can easily be scratched off. When the asphaltum is dry, draw a design on it with white ink; scrollwork or fancy floral designs are very effective. With a needle scratch the outline of the design on the glass, then, with a sharp knife, remove all of the asphaltum between the lines. Now place tinfoil over the design and glue it to the asphaltum. The more the tinfoil is crinkled before it is glued, the greater will be its effective- ness. Place the photograph in the space provided, and cover the entire 112 back, 7. e., the asphaltum side, with thin cardboard or stiff paper, and frame if desired. Instead of using crinkled tinfoil to fill in the designs, colored paper or celluloid may be used. Attractive photograph-frames and card - trays may be made in this manner. Crinkled tinfoil forms an attractive background for the scrolls on the asphalt-covered glass RE

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til |! Popular Science Monthly he instrument chosen y the greatest artists Cau these great a records for the Victor‘ ALDA BESANZONI BORI BRASLAU CALVE CARUSO CLEMENT CULP DeGOGORZA DeLUCA DESTINN EAMES FARRAR GALLI-CURCIi , GARRISON GIGLI GLUCK HARROLD HOMER JOHNSON JOURNET MARTINELLI i McCORMACK HH MELBA Hi MURPHY Ail RUFFO A SCHUMANN-HEINK Alt SCOTTI ALVIN SEMBRICH ANY TETRAZZINI WW} WERRENRATH | WHITEHILL H WITHERSPOON AH ZANELLI NAH ZEROLA | Violin ELMAN HEIFETZ KREISLER KUBELIK ZIMBALIST HH Piano AM ‘ ‘ CORTOT i The most cherished possession of the great PADEREWSKI | RACHMANINOFF singers and instrumentalists is their art, and their Violoncello KINDLER keenest desire is that under all circumstances they Orchestra . — caat PI 1 shall be heard at their best. It is in appreciation of ONZALEY T ° e 2 . Mh VICTOR HERBERT'S this fact that the greatest artists of this generation ae TOSCANINI AND LASCALA PHILA. SYMPHONY have become Victor artists, and their unqualified ALSO RECORDS BY THE pares DARtuate Meniane, Sameer endorsement of the Victrola is the most conclusive AND WILLIAMS a) evidence of its artistic superiority. so ERTETEES Tee LS | )) Ee aN There are Victrolas in great variety of styles from ee $25 to $1500. Victor dealers everywhere. Victor Talking Machine Co. Camden, New Jersey "HIS MASTERS VOICE” 4 This trademark and the trademarked word“ Victrola” identify all our products. Look under the lid! Look on the label! & VICTOR TALKING MACHINE CO Camden, N. J. REG. U.S. PAT. OFF. NW4I NE OSS NB Ao Eta RENONG LP we 078 —“ eS PSP DST DSS SEE

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If you must wait awhile before building all anew—why not “LOVELIFY” the PRESENT HOME by ADDING A CYPRESS TRELLIS—& AN ARBOR—& A NOOK? “Puttering Around” on Such Things Will Make This “The Happiest Summer Yet.” You can do it yourself. and WE CAN HELP by sending you at once that great big VOLUME 28 with full Working Plans of 19 Psa DESIGNS — complete Specifications and an Extra Supplement on ‘‘What Values & When” You will enjoy the 27 PICTURES and 2 valuable charts, and will not forget to specify and insist on CYPRESS (ofcourse) —not to please us, but because it is ‘* The Wood Eternal’’ and saves you the bother of repair bills. Here are 3 of the 19— all special designs by well-known architects —not one can be | bought—but all are | yours free with our compliments in Volume 28. The 3 articles and 2 planting charts on Vines are alone worth 50 times or more the stamp it costs to get this book. Out-of-Door Days Now—Also ask for Vol. 35. Cypress Sleeping Porches, &c—7 Designs The Cypress “Pergola-Garage” This Pergola-Garage is AN ADDED SUPPLEMENT to the 9th big reprint of VOLUME 28 of that home- lovers’ guide, counselor and impartial friend, the famous Cypress Pocket Library. It’s FREE. Will you write? When planning a Pergola, Mansion, Bungalow or sleeping porch, remember, ‘With CYPRESS you BUILD BUT ONCE.” Let our “ALL-ROUND HELPS DEPARTMENT” help YOU MORE. Our entire resources are at your service with Reliable Counsel. SOUTHERN CYPRESS MANUFACTURERS’ ASSOCIATION 1249 Perdido Building, New Orleans, La. or 1249 Heard National Bank Bldg., Jacksonville, Fla. INSIST ON TRADE-MARKED CYPRESS AT YOUR LOCAL LUMBER z 2 DEALER’S IF HE HASN'T IT, LET US KNOW IMMEDIATELY: Tee Mann Ree US Par Orree —CYPRESS “THE WOOD ETERNAL COMPLETE SPECIFICATIONS and Full WORKING PLANS FREE for this cozy, artistic and practical little CYPRESS “BUNGALOW B” if you send your name on a card TODAY to SOUTHERN CYPRESS MFRS.’ ASSN. 1249 Perdido Building, New Orleans, La. or 1249 Heard National Bank Bldg., Jacksonville, Fla. Popular Science Monthly Popular Science Monthly MAY, 1921 Volume 98-No.5 | sc llecacebeaiaatae Important to Readers Owing to the paper short- age, the number of printed copies of POPULAR SCIENCE MONTHLY is limited. To insure getting your maga- zine regularly, you should place a standing order with your newsdealer, or send us your yearly subscription of $3.00. CONTENTS AERONAUTICS Stunting as a Profession Airplane Wings that Fold To Photograph a Movie Battle Airplane Engine Cooled a New Way This Airplane Runs on Rails. . . FOR THE FARMER Caging the Corn to Foil Rats Digging Trenches Eight Feet a Minute Making a Mail-Box Out of a Barrel . Ree With This Plow a Horse Is Not Necessary. . Cement Wallows for Pigs : Gather Corn by Machine This Egg-Turner Is Simple Carriers that Preserve Fruit HOUSEKEEPING MADE EASY To Hear the Baby Cry One Stove Heats Four Rooms.. INDUSTRIAL PROGRESS The Tractor in the Factory Ear Books for the Blind Water Starts Radio Alarm Revolutionizing the Glass-Blowing Industry... Protecting a New Road It’s All in One Piece Pumping Sand for the Engine Peach-Stones as a Substitute for Coal Learning to Crate and Box in School The Machine Rotates and Plates Tipping the Whole Freight-Car Keeping the Grinding- Wheels Wet Glue Made of Blood MEDICINE AND SURGERY Hiccoughs—the Cause and Cure............. Broken Limbs Exercised in Bed Curing the “Bad Eye’’ Habit (Continued on page 4) ee ee eeeeees ee eee eeee Weer A ND BOOTIES. 6 coc ceed cccecivces DT nieey A OIE ROE so n.0:9 6 00.50 ba 5000's os 21 3B 39 58 39 42 46 46 47 65 65 36 42 Copyright, 1921, by the Modern Publishing Company POPULAR SCIENCE MONTHLY is issued monthly. Yearly subscription in the United States, $3.00, Canada, $3.50. Foreign, $4.00. Single copy, 25 cents, Advertising rates on application. Forms close the twentieth of the second month preceding date of publication. Entered as second-class matter Dec. 28, 1915, at the Post Office at New York under the act of March 3, 1879. Entered as second-class mate ter at the Post Office Department, Canada. The contents of this magazine are copyrighted and must not be reprinted without permission. H. J. Fisher, President; R. C. Wilson, Vice-President; O. B. Capen, Secretary and Treasurer. Modern Publishing Company New York City 225 West Thirty-ninth St. \ stor Ang see 1 grou they and alrp safe K was ovel glov face whe ng T that rew whe stre tion pho | aip abo Seal tha the