** How to Make a Flash Lamp [174]

Indoor photographs are made much better with the use of a flashlight than by depending on light from windows. The lighting can be made from any direction to suit the operator. If lighting flash powder when not in a regular flash lamp the flash cannot be depended upon and in some instances is dangerous. To make a simple and inexpensive flash lamp, first secure from your druggist an empty salve box about 3 in. in diameter. While at the drug store get 3 ft. of small rubber tubing; this will cost about 15 cents. Now visit the tin shop and get a small piece of scrap tin 3 or 4 in. square; a piece of brass or steel wire, about the size of stove pipe wire, 14 in. long. These with a strip of light asbestos paper and some small iron wire, about the size of door screen wire, will complete the material list.

Carefully punch a hole through the salve box on one side near the bottom with a 10-penny nail. Cut a strip of tin 2 in. long and about 3/8 in. wide and roll this around a 8-penny nail so as to form a small tube which will just fit the hole made in the salve box. Next roll up a strip of tin 1/2 in. wide into a small cup about 3/8 in. in diameter at one end and 1/4 in. at the other.

Place the tube in the nail hole so that one end comes almost to the center of the box inside and the other end projects about 1/2 in. outside the box. Cut out a little place for the tube to enter the cup at the small end and then solder the tube and cup to the bottom of the box as shown in the illustration. The tube and cup should be well soldered on the seams to make them airtight. Bend a ring on one end of the larger piece of wire, making it 2-1/2 in. in diameter and form the remaining portion of the wire into a spiral, soldering the end in the bottom of the box near the cup. Wrap the ring at the top of the spiral piece of wire all the way



around with the strip of asbestos paper, wrapping them together over and over until the entire ring is covered. Slip the end of the rubber tube over the tin tube on the side of the box and the flash lamp is complete.

To make a flash with this lamp fill the little cup in the center with flash powder and moisten the asbestos ring with alcohol. When all is ready for the picture the alcohol is lighted and a quick blow of the breath through the rubber tube will force the flash powder upward into the flame and cause the flash.

When through with the lamp place the cover over it, pushing the asbestos ring down inside the box. Wind the rubber tubing around the box and you have a neat outfit that can be carried in the pocket.



** Photographing the New Moon [174]

To make a photograph of the moon is quite difficult and no good picture can be made without an expensive apparatus. At home and with your own hand camera you can make a good picture of the new moon by the use of a flash light on a tennis ball, the tennis ball taking the part of the moon. The ball is suspended in front of a black cloth screen, the camera focused by holding a burning match near the ball and the exposure made by burning a



small quantity of flash powder at one side and a little below the ball. The light from the flash only striking one side of the ball gives the effect of the new moon. —Photo by M. M. Hunting, Dayton, O.



** Old-Time Magic- Part II [175]



** Removing Scissors from a Cord [175]

A piece of strong cord is doubled and fastened to a pair of scissors with a slip knot, as shown in Fig. 1. After passing the ends of the cord through the thumb hole of the scissors they are tied fast to a chair, door knob or any other object that may be of sufficient size to make the ends secure. The trick is to release the scissors without cutting the cord.

Take hold of the loop end of the cord in the lower handle and drawing it first



through the upper handle and then completely over the blades of the scissors, as shown in Fig. 2. This is very simple when you know how, but puzzling when the trick is first seen.



** Coin and Card on the First Finger [175]

This is a simple trick that many can do at the first attempt, while others will fail time after time. It is a good trick to spring upon a company casually if you have practiced it beforehand. A playing card is balanced on the tip of the forefinger and a penny placed on top immediately over the finger end, as shown in the sketch. With the right hand forefinger and thumb strike the edge of the card sharply. If done properly the card will flyaway, leaving the penny poised on the finger end.



** How to Make Sealing Wax Hat Pins [175]

Select a stick of sealing wax of the desired color for the foundation of the hat pin. Hold the end of the stick over a flame until the wax is soft enough to drop; then put it on the hat-pin head. When sufficient wax has adhered to the pin, hold the lump over the flame, revolving the pin at the same time so the wax will not drop and the head will form a round ball. The head can be made in any shape desired while warm. When the desired shape has been obtained, cool thoroughly in cold water and dry carefully.

Stripes and designs may be put on the foundation by applying drops of other brilliant colored wax, and by careful manipulation the wax when warm can be made to flow around the pin head and form pretty stripes and designs. If a certain color is to be more prominent, the wax to make this color must be applied last and the pin put through the flame again. Cool in water and dry, as before, and pass once more through the flame to obtain the luster.



** Old-Time Magic-Part III [176]



** Disappearing Coin [176]

While this is purely a sleight-of-hand trick, it will take very little practice to cause the coin to disappear instantly. Take a quarter of a dollar between the thumb and finger, as shown, and by a rapid twist of the fingers whirl the coin and at the same time close the hand, and the coin will disappear up your coat sleeve. On opening the hand the coin will not be seen. Take three quarters and hold one in the palm of the left hand, place the other two, one between the thumb and finger of each hand, then give the coin in the right hand a whirl, as described, closing both hands quickly. The coin in the right hand will disappear up your sleeve, and the left hand on being unclosed will contain two quarters, while the one in the right shall have disappeared.



** Sticking a Coin Against the Wall [176]

Cut a small notch in a coin—ten cent piece or quarter will do—so a small point will project. When this is pressed firmly against a wood casing or partition the coin will stick tightly.



** A Chinese Outdoor Game [176]

The accompanying illustration shows the "grand whirl," or the Chinese students' favorite game. This game is played by five persons, four of them turning around the fifth or central figure



with their arms locked about each other and the two outside persons swinging in midair with their bodies almost horizontal.



** Home-Made Photograph of a Lightning Flash [176]

How many times has each amateur photographer tried to photograph the lightning's flash? Some good pictures have been obtained by a ceaseless effort on the part of the operator. Here is a method by which you can make a picture of a streak of lightning on a clear night in your own house. Paste two strips of black paper on a piece of glass that is 10 in. square so as to leave a clear space through the center 2-in. or more in width. Smoke this uncovered space over a candle's flame until the soot is thick enough to prevent light passing through. Take a sharp lead pencil and outline a flash of lightning upon the smoked surface, using a fine needle to make the smaller lines, and then set the glass up against the back of two boxes which are set to have a space between them of 4 or 5 in.

A lighted candle is held behind the glass so the light will shine through for focusing the camera. After darkening the room set your camera ready for the exposure and burn a small quantity of flash light powder in the same place in which the candle was held. This will make an impression upon the plate of the flash drawn on the smoked glass.



** How to Make a Static Machine [177]

Static electricity is produced by revolving glass plates upon which a number of sectors are cemented; these sectors, passing through neutralizing brushes, distribute electric charges



to collecting combs attached to discharging rods. The glass selected for the plates must be clear white glass, free from wrinkles, and of a uniform thickness. Two plates are necessary to make this machine, and the glass should be of sufficient size to cut a circular plate 16-in. in diameter. A hole must be made exactly in the center of each plate, and this should be done before cutting the circle. One of the best ways to make the hole is to drill the glass with a very hard-tempered drill, the cutting edge of which should be kept moistened with 2 parts turpentine and 1 part sweet oil while drilling. The hole is to be made 3/4 in. in diameter. The circle is then marked on each plate and cut with a glass cutter. The plates are trued up, after they are mounted, by holding a piece of emery wheel to the edges while they are turning. Water should be applied to the edges while doing the work.

The sectors are cut from tinfoil, 1-1/2 in. wide at one end, 3/4 in. at the other, and 4 in. long. A thin coat of shellac varnish is applied to both sides of the plates, and 16 sectors put on one side of each plate, as shown in Fig. 1. The divisions can be marked on the opposite side of the plate and a circle drawn as a guide to place the sectors at proper intervals.

The sectors should lie flat on the glass with all parts smoothed out so that they will not be torn from their places as the plates revolve. The shellac should be tacky when the pieces of tinfoil are put in place.

The collectors are made, as shown in Fig. 2, from about 1/4-in. copper wire with two brass balls soldered to the ends. The fork part is 6 in. long and the shank 4 in. Holes are drilled on the inside of the forks, and pins inserted and soldered. These pins, or teeth, should be long enough to be very close to the sectors and yet not scratch them when the plates are turning.

The frame of the machine is made from any kind of finished wood with dimensions shown in Fig. 3, the side pieces being 24 in. long and the standards 3 in. wide. The two pieces, C C, Fig. 3, are made from solid, close grained wood turned in the shape shown, with the face that rests against the plate 4 in. in diameter, and the outer end 1-1/2 in. in diameter, the smaller end being turned with a groove for a round belt. Before turning the pieces a hole is bored through each piece for the center, and this hole must be of such a size as to take a brass tube that has an internal diameter of 3/4 in. The turned pieces are glued to the glass plates over the center holes and on the same side on which the sectors are fastened. Several hours' time will be required for the glue to set. A fiber washer is then put between the plates and a brass tube axle placed through the hole. The plates, turned wood pieces, and brass axle turn on a stationary axle, D.

The drive wheels, EE, are made from 7/8-in. material 7 in. in diameter, and are fastened on a round axle cut from a broom handle. This wood axle is centrally bored to admit a metal rod tightly, and extends through the standards with a crank attached to one end.

Two solid glass rods, GG, Fig. 4, 1 in. in diameter and 15 in. long, are fitted in holes bored into the end pieces of the frame. Two pieces of 1-in. brass tubing and the discharging rods, RR, are soldered into two hollow brass balls 2 or 2-1/2 in. in diameter. The shanks of the collectors are fitted in these brass balls with the ends extending, to which insulating handles are attached. Brass balls are soldered to the upper ends of the discharging rods, one having a 2-in. ball and the other one 3/4 in. in diameter.

Caps made from brass are fitted tightly on the ends of the stationary shaft, D, and drilled through their diameter to admit heavy copper rods, KK, which are bent as shown. Tinsel or fine wire such as contained in flexible electric wire are soldered to the ends of these rods, and the brushes thus made must be adjusted so they will just touch the plates. The caps are fitted with screws for adjusting the brushes. These rods and brushes are called the neutralizers. A little experimenting will enable one to properly locate the position of the neutralizers for best results. —Contributed by C. Lloyd Enos, Colorado City, Colo.



** A Concrete Swimming Pool [178]



Several boys from a neighborhood in the suburbs of a large city concluded to make for themselves a swimming tank of concrete. The money was raised by various means to purchase the cement, and the work was done by themselves. The ground was selected in a secluded spot in a neighbor's back yard and a hole dug to a depth of 4 ft., 12 ft. wide and 22 ft. long. The concrete was made by mixing 1 part cement, 4 parts sand and 10 parts gravel together and the bulk moistened with water. The bottom was made the same as laying a sidewalk, and forms were only used for the inside of the surrounding wall. The tank may be hidden with shrubbery or vines planted to grow over a poultry wire fence.



** Old-Time Magic-Part IV [179]

Cutting a Thread Inside of a Glass Bottle [179]

This is a trick which can only be performed when the sun shines, but it



is a good one. Procure a clear glass bottle and stick a pin in the lower end of the cork. Attach a thread to the pin and tie a small weight to the end of the thread so it will hang inside the bottle when the cork is in place. Inform your audience that you will sever the thread and cause the weight to drop without removing the cork.

All that is required to perform the feat is to hold a magnifying glass so as to direct the sun's rays on the thread. The thread will quickly burn and the weight fall.



** Removing a Key from a Double String [179]

Tie the ends of a 5-ft. string together, making a double line on which a key is placed and the string held as shown by the dotted lines in the sketch. Turn the palms of the hands toward you and reach over with the little finger of the right hand and take hold of the inside line near the left-hand thumb.



Reverse the operation and take hold of the inside line near right-hand thumb with the little finger of the left hand. You will then have the string as it appears in the sketch. Quickly let loose of the string with a little finger on one hand and a thumb on the other and pull the string taut. The key will drop from the string.



** How to Bore a Square Hole [179]

You would not consider it possible to bore a square hole in a piece of cardboard, yet such a thing can be done. Take a cardboard or a thin piece of wood, fold and place it between two pieces of board with the fold up; the boards are then put in a vise as shown. Start the bit with the screw point in the fold, using a 1-in. bit, and bore a



hole 1/2 in. deep. When the cardboard is taken from the vise it will appear as shown at B and when unfolded, as at A.



** HOW TO MAKE COPPER TRAYS [180]

Copper trays such as are shown in the accompanying illustration are very useful as well as ornamental about the house. They can be used to keep pins and needles, pens and pencils, or cigar ashes, etc. They are easily made, require no equipment in the way of tools except what are usually found about the house, unless it would be the metal shears, and when the decorations are well designed and the metal nicely colored, they make attractive little pieces to have about.

The first thing to do in preparation for making them is to prepare the design. Simple designs work out better than fussy ones and are more likely to be within the ability of the amateur. Having determined the size of the tray, draw on paper an oblong to represent it. Inside this oblong, draw another one to represent the lines along which the metal is to be bent up to form the sides. Inside this there should be drawn still another oblong to represent the margin up to which the background is to be worked. The trays shown are 5-3/4 by 6-3/4 in., the small ash tray 4 by 4 in., the long pen and pencil tray 4-3/4 by 9-1/2 in. The second oblong was 3/4 in. inside the first on all, and the third one 1/4 in. inside the second on all.

If the decoration is to have two parts alike—symmetrical—divide the space with a line down the middle. Draw one-half the design free hand, then fold along this line and trace the second half from this one. If the lines have been drawn with soft pencil, rubbing the back of the paper with a knife handle will force enough of the lead to the second side so that the outline can be determined. Four-part symmetry will require two lines and two foldings, etc.

For the metal working there will be needed a pair of tin shears, two spikes, file, flat and round-nosed pliers, screw-driver and sheet copper of No. 23 gauge. Proceed as follows: 1. Cut off a piece of copper so that it shall have 1/2 in. extra metal on each of the four sides. 2. With a piece of carbon paper trace upon the copper lines that



shall represent the margin of the tray proper and the lines along which the upturned sides of the tray are to be bent; also trace the decorative design. 3. With a nail make a series of holes in the extra margin, about 3/4-in. apart and large enough to take in a 3/4-in. slim screw. 4. Fasten the metal to a thick board by inserting screws in these holes. 5. With a 20-penny wire nail that has the sharpness of its point filed off, stamp the background promiscuously. By holding the nail about 1/4 in. above the work and striking it with the hammer, at the same time striving to keep it at 1/4 in. above the metal, very rapid progress can be made. This stamping lowers the background and at the same time raises the design. 6. Chase or stamp along the border of the design and background, using a nail filed to chisel edge. This is to make a clean, sharp division between background and design. 7. When the stamping is completed, remove the screws and the metal from the board and cut off the extra margin with the metal shears. File the edges until they are smooth to the touch. 8. With the flat pliers "raise" one side of the tray, then the other side. 9. Raise the ends, adjusting the corners as shown in the illustration. Use the round-nosed pliers for this purpose.

Copper is frequently treated chemically to give it color. Very pretty effects may be obtained by covering the tray with turpentine, then moving it about over a flame such as a bunsen burner until the turpentine burns off. The copper will "take on" almost all the colors of a rainbow, and the effect will be most pleasing.



** Photograph of a Clown Face [181]

At first glance the accompanying photograph will appear as if the person photographed is wearing a false face or has his face painted like a clown. On close observation you will notice that the face is made on the bald head of the person sitting behind the table. The eyes, nose and mouth are cut from black paper and pasted on the bald spot. The subject's face is horizontal and resting upon his hands.



** Finger Mathematics [181] By Charles C. Bradley

All machinists use mathematics. Ask a machinist what would be the product of 9 times 8 and his ready reply would be 72, but change the figures a little and say 49 times 48 and the chances are that instead of replying at once he will have to figure it out with a pencil. By using the following method it is just as easy to tell at a glance what 99 times 99 are as 9 times 9. You will be able to multiply far beyond your most sanguine expectations.

In the first numbering, begin by holding your hands with the palms toward the body and make imaginary numbers on the thumbs and fingers as follows: Thumbs, 6; first fingers, 7; second fingers, 8; third fingers, 9, and fourth fingers, 10. Suppose you desire to multiply 8 by 9, put the eighth finger on one hand against the ninth finger of the other hand as shown.



The two joined fingers and all the fingers above them (calling the thumbs fingers) are called the upper fingers and each has a value of ten, which tens are added. All the fingers below the joined fingers are termed the lower fingers, and each of the lower fingers represents a unit value of one. The sum of the units on one hand should be multiplied by the sum of the units on the other hand. The total tens added to this last named sum will give the product desired. Thus: Referring to above picture or to your hands we find three tens on the left hand and four tens on the right, which would be 70. We also find two units on the left hand and one on the right. Two times one are two, and 70 plus 2 equals 72, or the product of 8 times 9.

Supposing 6 times 6 were the figures. Put your thumbs together; there are no fingers above, so the two thumbs represent two tens or 20; below the thumbs are four units on each hand, which would be 16, and 20 plus 16 equals 36, or the product of 6 times 6.



Supposing 10 times 7 is desired. Put the little finger of the left hand against the first finger of the right hand. At a glance you see seven tens or 70. On the right hand you have three units and on the left nothing. Three times nothing gives you nothing and 70 plus nothing is 70.

In the second numbering, or numbers above 10, renumber your fingers; thumbs, 11; first fingers, 12, etc. Let us multiply 12 by 12.

Put together the tips of the fingers labeled 12. At a glance you see four tens or 40. At this point we leave the method explained in Case 1 and ignore the units (lower fingers) altogether. We go back to the upper fingers again



and multiply the number of upper fingers used on the one hand by the number of upper fingers used on the other hand, viz., 2 times 2 equals 4. Adding 4 to 40 gives us 44. We now add 100 (because anything over 10 times 10 would make over 100) and we have 144, the product of 12 times 12.

The addition of 100 is arbitrary, but being simple it saves time and trouble. Still, if we wish, we might regard the four upper fingers in the above example as four twenties, or 80, and the six lower fingers as six tens, or 60; then returning to the upper fingers and multiplying the two on the right hand by the two on the left we would have 4; hence 80 plus 60 plus 4 equals 144; therefore the rule of adding the lump sum is much the quicker and easier method.

Above 10 times 10 the lump sum to add is 100; above 15 times 15 it is 200; above 20 times 20, 400; 25 times 25, 600, etc., etc., as high as you want to go.

In the third numbering to multiply above 15 renumber your fingers, beginning the thumbs with 16, first finger 17, and so on. Oppose the proper finger tips as before, the upper fingers representing a value of 20. Proceed as in the first numbering and add 200. Take For example 18 times 18.

At a glance we see six twenties plus 2 units on left hand times 2 units on right hand plus 200 equals 324.

In the fourth numbering the fingers are marked, thumbs, 21, first fingers 22, etc., the value of the upper fingers being 20. Proceed as in the second lumbering, adding 400 instead of 100.



Above 25 times 25 the upper fingers represent a value of 30 each and after proceeding as in the third numbering you add 600 instead of 200.

This system can be carried as high as you want to go, but you must remember that for figures ending in 1, 2, 3, 4 and 5 proceed as in the second numbering. For figures ending in 6, 7, 8, 9 and 10 the third numbering applies.

Determine the value of the upper fingers whether they represent tens, twenties, thirties, forties, or what. For example, any two figures between 45 and 55, the value of the upper fingers would be 50, which is the half-way point between the two fives. In 82 times 84 the value of the upper fingers would be 80 (the half-way point between the two fives, 75 and 85, being 80). And the lump sum to add.

Just three things to remember:

Which numbering is to follow, whether the one described in second or third numbering; the value which the upper fingers have; and, lastly, the lump sum to add, and you will be able to multiply faster and more accurately than you ever dreamed of before.



** Optical Illusions [183]

If a person observes fixedly for some time two balls hanging on the end of cords which are in rapid revolution, not rotation, about a vertical axis, the direction of revolution will seem to reverse. In some experiments two incandescent "pills" of platinum sponge, such as an used for lighting gas-burners, were hung in tiny aluminum bells from a mica vane wheel which was turned constantly and rapidly in one direction by hot air from a gas flame to keep the platinum in a glow. The inversion and reversion did not take place, as one might suppose, at the will of the observer, but was compulsory and followed regular rules. If the observer watches the rotating objects from the side, or from above or from below, the inversion takes place against his will; the condition being that the image on the retina shall be eccentric. It takes place also, however, with a change in the convergence of the optical axes, whether they are parallel to each other or more convergent. Also when the image on the retina is made less distinct by the use of a convex or concave lens, the revolution seems to reverse; further, in the case of a nearsighted person, when he removes his spectacles,



inversion results every time that the image on the retina is not sharp. But even a change in the degree of indistinctness causes inversion.

The cause of this optical illusion is the same where the wings of windmills are observed in the twilight as a silhouette. It is then not a question of which is the front or the back of the wheel, but whether one of the wings or the other comes towards the observer. The experiment is made more simple by taking a hat pin with a conspicuous head, holding it firmly in a horizontal position, and putting a cork on the point. Looking at it in semi-darkness, one seems to see sometimes the head of the pin, sometimes the point towards him, when he knows which direction is right. The inversion will be continued as soon as one observes fixedly a point at the side. Here it is a question of the perception of depth or distance; and this is the same in the case of the rotating balls; the direction of seeming revolution depends on which one of them one considers to be the front one and which the rear one.

From the foregoing the following conclusion may be reached: When, in the case of a perception remitting two appearances, one fixedly observes one of these and then permits or causes change in the sharpness of the image on the retina, the other appearance asserts itself.



** Steam Engine Made from Gas Pipe and Fittings [184]

Almost all the material used in the construction' of the parts for the small steam engine illustrated herewith was made from gas pipe and fittings. The cylinder consists of a 3-in. tee, the third opening being threaded and filled with a cast-iron plug turned to such a depth that when the interior was bored out on a lathe the bottom of the plug bored to the same radius as the other part of the tee. The outside end of the plug extended about 1/4-in. and the surface was made smooth for the valve seat. A flat slide valve was used.

The ports were not easy to make, as



they had to be drilled and chipped out. The steam chest is round, as it had to be made to fit the round tee connection. The crosshead runs in guides made from a piece of gas pipe with the sides cut out and threads cut on both ends. One end is screwed into a rim turned on the cylinder head and the other is fitted into an oblong plate. Both ends of this plate were drilled and tapped to receive 1-1/2-in. pipe.

The main frame consists of one 1-1/2in. pipe 10 in. long and one made up from two pieces of pipe and a cross to make the whole length 10 in. These pipes were then screwed into pipe flanges that served as a base. The open part of the cross was babbitted to receive the main shaft. The end of the shaft has a pillow block to take a part of the strain from the main bearing. The eccentric is constructed of washers. While this engine does not give much power, it is easily built, inexpensive, and anyone with a little mechanical ability can make one by closely following out the construction as shown in the illustration. —Contributed by W. H. Kutscher, Springfield, Ill.



** How to Make a Copper Bowl [185]

To make a copper bowl, such as is shown in the illustration, secure a piece of No. 21 gauge sheet copper of a size sufficient to make a circular disk 6-1/2 in. in diameter.

Cut the copper to the circular form and size just mentioned, and file the edge so that it will be smooth and free from sharp places. With a pencil compass put on a series of concentric rings about 1/2 in. apart. These are to aid the eye in beating the bowl to form.

The tools are simple and can be made easily. First make a round-nosed mallet of some hard wood, which should have a diameter of about 1-1/4 in, across the head. If nothing better is at hand, saw off a section of a broom handle, round one end and insert a handle into a hole bored in its middle. Next take a block of wood, about 3 by 3 by 6 in., and make in one end a hollow, about 2 in. across and 1/2 in. deep. Fasten the block solidly, as in a vise, and while holding the copper on the hollowed end of the block, beat with the mallet along the concentric rings.

Begin at the center and work along the rings—giving the copper a circular movement as the beating proceeds—out toward the rim. Continue the circular movement and work from the rim back toward the center. This operation is to be continued until the bowl has the shape desired, when the bottom is flattened by placing the bowl, bottom side up, on a flat surface and beating the raised part flat. Beating copper tends to harden it and, if continued too long without proper treatment, will cause the metal to break. To overcome this hardness, heat the copper over a bed of coals or a Bunsen burner to a good heat. This process is called annealing, as it softens the metal.

The appearance of a bowl is greatly enhanced by the addition of a border. In the illustration the border design shown was laid out in pencil, a small hole was drilled with a band drill in each space and a small-bladed metal saw inserted and the part sawed out.

To produce color effects on copper, cover the copper with turpentine and



hold over a Bunsen burner until all parts are well heated.



** Cleaning Furniture [185]

After cleaning furniture, the greasy appearance may be removed by adding some good, sharp vinegar to the furniture polish. Vinegar, which is nothing else than diluted acetic acid, is one of the best cleansers of dirty furniture.



** Melting Lead in Tissue Paper [185]

Take a buckshot, wrap it tightly in one thickness of tissue paper, and, holding the ends of the paper in the fingers of each hand, place the part that holds the shot over the flame of a match just far enough away from the flame not to burn the paper. In a few seconds unfold the paper and you will find that the shot has melted without even scorching the paper. —Contributed by W. O. Hay, Camden, S. C.



** The Principles of the Stereograph [185]

Each of our eyes sees a different picture of any object; the one sees a trifle more to the right-hand side, the other to the left, especially when the object is near to the observer. The stereoscope is the instrument which effects this result by bringing the two pictures together in the senses. The stereograph produces this result in another way than by prisms as in the stereoscope. In the first place there is



only one picture, not two mounted side by side. The stereograph consists of a piece of card, having therein two circular openings about 1-1/4 in. diameter, at a distance apart corresponding to the distance between the centers of the pupils. The openings are covered with transparent gelatine, the one for the left eye being blue, that for the right, orange. The picture is viewed at a distance of about 7 in. from the stereograph. As a result of looking at it through the stereograph, one sees a colorless black and white picture which stands out from the background. Try looking at the front cover of Popular Mechanics through these colored gelatine openings and the effect will be produced.

If one looks at the picture first with the right eye alone through the orange glass, and then with the left eye through the blue glass, one will understand the principle on which the little instrument works. Looking through the blue glass with the left eye, one sees only those portions which are red on the picture. But they seem black. The reason is that the red rays are absorbed by the blue filter. Through the orange gelatine all the white portions of the picture seem orange, because of the rays coming from them, and which contain all the colors of the spectrum; only the orange rays may pass through. The red portions of the picture are not seen, because, although they pass through the screen, they are not seen against the red ground of the picture. It is just as though they were not there. The left eye therefore sees a black picture on a red background.

In the same way the right eye sees through the orange screen only a black picture on a red background; this black image consisting only of the blue portions of the picture. Any other part of complementary colors than blue and orange, as for instance red and green, would serve the same purpose.

The principle on which the stereograph works may be demonstrated by a very simple experiment. On white paper one makes a picture or mark with a red pencil. Looking at this through a green glass it appears black on a green ground; looking at it through a red glass of exactly the same color as the picture, it, however, disappears fully.

Through the glass one will see only a regular surface of the color of the glass itself, and without any picture. Through a red glass a green picture will appear black.

So with the stereograph; each eye sees a black picture representing one of the pictures given by the stereoscope; the only difference being that in the case of the stereograph the background for each eye is colored; while both eyes together see a white background.

In the pictures the red and the green lines and dots must not coincide; neither can they be very far apart in order to produce the desired result. In order that the picture shall be "plastic," which increases the sense of depth and shows the effect of distance in the picture, they must be a very trifle apart. The arrangement of the two pictures can be so that one sees the pictures either in front of or on the back of the card on which they are printed. In order to make them appear before the card, the left eye sees through a blue screen, but the red picture which is seen by it is a black one, and lies to the right on the picture; and the right eye sees the lefthand picture. The further apart the pictures are, the further from the card will the composite image appear.

In the manufacture of a stereoscope the difficulty is in the proper arrangement of the prisms; with the stereograph, in the proper choice of colors.



** Mercury Make-and-Break Connections for Induction Coils [187]

Induction coils operating on low voltage have a make-and-break connection called the "buzzer" to increase the secondary discharge. Two types of make-and-break connection are used, the common "buzzer" operated by the magnetism of the core in the coil and the mercury break operated by a small motor. The sketch herewith shows how to make the motor-operated break. Two blocks of wood are nailed together in the shape of an L and a small motor fastened to the top of the vertical piece. The shaft of the motor is bent about 18 in. in the shape of a crank, so that in turning it will describe a circle 1/4 in. in diameter. A small connecting bar is cut from a piece of brass 1/8 in. thick, 1/4 in. wide and 1 in. long and a hole drilled in each end; one hole to fit the motor shaft and the other to slip on a No. 12 gauge wire. Two L-shaped pieces of brass are fastened to the side of the block and drilled with holes of such a size that a No. 12 gauge wire will slip through snugly. Place a NO.12 gauge wire in these holes and bend the top end at right angles.



Put the connecting brass bar on the motor shaft with washers fitted tight on each side and slip the other end over the bent end of the wire. Have the wire plenty long so it can be cut to the proper length when the parts are all in place. A small round bottle about 1/2 in. in diameter is now fitted in a hole that has been previously bored into the middle of the bottom block and close up to the vertical piece. This should only be bored about half way through the block. The wire is now cut so at the length of the stroke the end will come to about one-half the depth, or the middle of the bottle.

Fill the bottle with mercury to a point so that when the motor is running, the end of the wire will be in the mercury for about one-half of the stroke. Cover the mercury over with a little alcohol. A No. 14 gauge iron wire is bent and put into the side of the bottle with the end extending to the bottom. The other end of this wire is attached to one binding-post placed at the end of the bottom block. The other binding-post is connected to a small brass brush attached to the side of the vertical piece, which is placed with some pressure on the moving wire. The motor can be run with a current from a separate course or connected as shown on the same batteries with the coil. The proper height of the mercury can be regulated for best results. The motor must run continuous if the coil is used for writing code signals, wireless, etc. —Contributed by Haraden Pratt, San Francisco, Cal.



** How to Make a Barometer [188]

Atmospheric pressure is measured by the barometer. The weight of the air in round numbers is 15 lb. to the square inch and will support a column of water 1 in. square, 34 ft. high, or a column of mercury (density 13.6) 1 in. square, 30 in. high. The parts necessary to make a simple barometer are, a glass tube 1/8 in. internal diameter and about 34 in. long, a bottle 1 in. inside diameter and 2 in. high. Seal one end of the tube by holding it in the flame of a gas burner, which will soon soften the glass so it can be pinched together with pliers. Put a little paraffin in the bottle and melt it by holding the bottle over a small flame. When cool the paraffin should cover the bottom about 1/16 in. thick. The tube is now to be filled with mercury. This may be accomplished with a paper funnel, but before attempting to put in the mercury, place a large dish or tray beneath the tube to catch any mercury that may accidentally be spilled. Only redistilled mercury should be used, and the tube should be perfectly clean before filling. When the tube is filled to



within 1 in. of the open end place the forefinger over the hole and tilt the tube up and down so all the air will gather at the finger end. The filling is continued until the tube is full of mercury. The glass bottle containing the wax covered bottom is now placed over the end of the tube and pressed firmly to insure an airtight fit with the tube. The bottle and tube are inverted and after a few ounces of mercury are put in the bottle the tube may be raised out of the wax, but be careful not to bring its edge above the surface of the mercury.

The instrument is put aside while the base is being made, or, if you choose, have the base ready to receive the parts just described when they are completed. Cut a base from a piece of 7/8-in. pine 3 in. wide and 40 in. long. In this base cut a groove to fit the tube and the space to be occupied by the bottle is hollowed out with a chisel to a depth of 3/4 in., so the bottle rests on one-half of its diameter above the surface of the board and one-half below. The instrument is made secure to the base with brass strips tacked on as shown in the sketch. After the instrument is in place put enough mercury in the bottle so the depth of the mercury above the bottom end of the tube will be about 1/2 in.

The scale is made on a piece or cardboard 2 in. wide and 4 in. long. The 4 in. are marked off and divided into sixteenths, and the inches numbered 27 up to 31. The scale is fastened to the base with glue or tacks and in the position behind the tube as shown in the sketch. Before fastening the scale, the instrument should be compared with a standard barometer and the scale adjusted so both readings are the same. But if a standard barometer is not available, the instrument, if accurately constructed, will calibrate itself.

In general, a drop in the mercury indicates a storm and bad weather, while a rise indicates fair weather and in winter a frost. Sudden changes in the barometer are followed by like changes in weather. The slow rise of the mercury predicts fair weather, and a slow fall, the contrary. During the frosty days the drop of the mercury is followed by a thaw and a rise indicates snow.



** Home-Made Post or Swinging Light [189]

Remove the bottom from a round bottle of sufficient size to admit a wax or tallow candle. This can be done with a glass cutter or a hot ring; the size of the outside of the bottle, which is slipped quickly over the end. Procure a metal can cover, a cover from a baking powder can will do, a lid fit it on the end where the bottom was removed. The cover is punched full of holes to admit the air and a cross cut in the center with the four wings thus made by the cutting turned up to form a place to insert the candle. The metal cover is fastened to the bottle with wires as shown in the sketch. This light can be used on a post or hung from a metal support.



** A Checker Puzzle [189]

Cut a block from a board about 3 in. wide and 10 in. long. Sandpaper all the surfaces and round the edges slightly. Mark out seven 1-in. squares on the surface to be used for the top and color the squares alternately white and black. Make six men by sawing a curtain roller into pieces about 3/8 in. thick. Number the pieces 1, 2, 3, 5, 6 and 7, and place them as shown in Fig. 1. The puzzle is to make the first three change places with the last three and



move only one at a time. This may be done as follows:

Move 1-Move No. 3 to the center. Move 2-Jump No. 5 over No. 3. Move 3-Move No. 6 to No. 5's place. Move 4-Jump No, 3 over No. 6. Move 5-Jump No. 2 over No. 5. Move 6-Move No. 1 to No. 2's place. Move 7-Jump No. 5 over No. 1. Move 8-Jump No. 6 over No. 2. Move 9-Jump No. 7 over No. 3. Move 10-Move No. 3 into No. 7's place. Move ll-Jump No. 2 over No. 7. Move 12-Jump No, l over No. 6. Move 13-Move No. 6 into No. 2's place. Move 14-Jump No. 7 over No. 1. Move 15-Move No. 1 into No, 5's place.

After the 15 moves are made the men will have changed places. This can be done on a checker board, as shown in Fig. 2, using checkers for men, but be sure you so situate the men that they will occupy a row containing only 7 spaces. —Contributed by W. L. Woolson, Cape May Point, N.J.



** Gold Railroad Signals [189]

Covering railroad signals with gold leaf has taken the place of painting on some roads. Gold leaf will stand the wear of the weather for 15 or 20 years, while paint requires recovering three or four times a year.



** How to Make a Bell Tent [190]

A bell tent is easily made and is nice for lawns, as well as for a boy's camping outfit. The illustrations show a plan of a tent 14-ft. in diameter. To make such a tent, procure unbleached tent duck, which is the very best material for the purpose, says the Cleveland Plain Dealer. Make 22 sections, shaped like Fig. 3, each 10 ft. 6 in. long and 2 ft. 2 in. wide at the bottom, tapering in a straight line to a point at the top. These dimensions allow for the laid or lapped seams, which should be



double-stitched on a machine. The last seam sew only for a distance of 4 ft. from the top, leaving the rest for an opening. At the end of this seam stitch on an extra gusset piece so that it will not rip. Fold back the edges of the opening and the bottom edge of the bell-shaped cover and bind it with wide webbing, 3 in. across and having eyelets at the seams for attaching the stay ropes. Near the apex of the cover cut three triangular holes 8 in. long and 4 in. wide at the bottom and hem the edges. These are ventilators. Make the tent wall of the same kind of cloth 2 ft. 2 in. high. Bind it at the upper edge with webbing and at the bottom with canvas. Also stitch on coarse canvas 6 in. wide at the bottom, and the space between the ground and the wall when the tent is raised, fill with canvas edging. Stitch the upper edge of the wall firmly to the bell cover at the point indicated by the dotted line, Fig. 2.

For the top of the tent have the blacksmith make a hoop of 1/4-in. round galvanized iron, 6-in. diameter. Stitch the canvas at the apex around the hoop and along the sides. Make the apex into a hood and line it with stiff canvas. Have the tent pole 3 in. in diameter, made in two sections, with a socket joint and rounded at the top to fit into the apex of the tent.

In raising the tent, fasten down the wall by means of loops of stout line fastened to its lower edge and small pegs driven through them into the ground, Fig. 5. Run the stay ropes from the eyelets in the circular cover to stakes (Fig. 5) stuck in the ground. Use blocks, as in Fig. 6, on the stay ropes for holding the ends and adjusting the length of the ropes.



** Simple X-Ray Experiment [190]

The outlines of the bones of the hand may be seen by holding a piece of rice paper before the eyes and placing the spare hand about 12 in. back of the rice paper and before a bright light. The bony structure will be clearly distinguishable. —Contributed by G.J. Tress, Emsworth, Pa.



** How to Make a Candle Shade [191]

Layout the pattern for the shade on a thin piece of paper, 9 by 12 in., making the arcs of the circle with a pencil compass. As shown in the sketch, the pattern for this particular shade covers a half circle with 2-3/4 in. added. Allowance must be made for the lap and as 1/4 in. will do, a line is drawn parallel 1/4 in. from the one drawn through the center to the outside circle that terminates the design.

Nail a thin sheet of brass, about 9 in. wide by 12 in. long, to a smooth board of soft wood, then trace the design on the brass by laying a piece of carbon paper between the pattern and the brass. After transferring the design to the brass, use a small awl to punch the holes in the brass along the outlines of the figures traced. Punch holes in the brass in the spaces around the outlined figures, excepting the 1/4-in. around the outside of the pattern. When all the holes are punched, remove the brass sheet from the board and cut it along the outer lines as traced from the pattern, then bend the brass carefully so as not to crease the figures appearing in relief. When the edges are brought together by bending, fasten them with brass-headed nails or brads.

If a wood-turning lathe is at hand, the shade can be made better by turning a cone from soft wood that will fit the sheet-brass shade after it is shaped and the edges fastened together. The pattern is traced as before, but before punching the holes, cut out the brass on the outside lines, bend into shape, fasten the ends together and place on the wood cone. The holes are now punched on the outlines traced from the pattern and the open spaces made full of holes. The holes being punched after the shade is shaped, the metal will stay and hold the perfect shape of a cone much better.

The glass-beaded fringe is attached on the inside of the bottom part with small brass rivets or brads placed about 3/4 in. apart. The thin sheet brass may be procured from the local hardware



dealer and sometimes can be purchased from general merchandise stores. —Contributed by Miss Kathryn E. Corr, Chicago.



** A Putty Grinder [191]

Having a large number of windows to putty each week, I found it quite a task to prepare the putty. I facilitated the work by using an ordinary meat cutter or sausage grinder. The grinder will soften set putty and will quickly prepare cold putty. It will not, however, grind old putty or make putty from whiting and oil. —Contributed by H. G. Stevens; Dunham, Que.



** Home-Made Small Churn [192]

Many people living in a small town or in the suburbs of a city own one



cow that supplies the family table with milk and cream. Sometimes the cream will accumulate, but not in sufficient quantities to be made into butter in a large churn. A fruit jar usually takes the place of a churn and the work is exceedingly hard, the jar being shaken so the cream will beat against the ends in the process of butter-making. The accompanying sketch shows clearly how one boy rigged up a device having a driving wheel which is turned with a crank, and a driven wheel attached to an axle having a crank on the inner end. This crank is connected to a swinging cradle with a wire pitman of such a size as to slightly bend or spring at each end of the stroke. The cradle is made with a cleat fastened to each end, between which is placed the fruit jar, partially filled with cream. The jar is wedged in between the cleats and the churning effected by turning the crank. —Contributed by Geo. E. Badger, Mayger, Oregon.



** Home-Made Round Swing [192]

Gas pipe and fittings were used wherever possible in the making of the swing as shown in the photograph. The d i a g ram drawing shows the construction. A 6-in. square cedar post is set in the ground about 3 ft., allowing 2 ft. to remain above the ground and a 7/8-in. piece of shafting is driven into the top part of this post for an axle. A cast-iron ring, or, better still, a heavy wheel with four spokes of such a size as to be drilled and tapped for 1/2-in. pipe is used for the hub, or center on which the frame swings. If a wheel is selected, the rim must be removed and only the spokes and hub used. The hole in the hub must be 7/8 in. or less, so the hub can be fitted to the shafting that is driven in the post. A large washer is placed on top of the post and the hub or cast-iron ring set on the washer.

The drilled and tapped holes in the four spokes are each fitted with a 4-1/2 length of 1/2-in. pipe. These pipes are



each fitted with a tee on the end and into this tee uprights of 1/2-in. pipe in suitable lengths are screwed, and also short lengths with a tee and axle for the 6-in. wheel are fitted in the under side of the tee. The uprights at their upper ends are also fitted with tees and each joined to the center pipe with 1/2-in. pipe flattened on the inner end and fastened with bolts to a flange.

The bottom part of the cloth covering is held in place by a 1/2-in. pipe, bent to the desired circle. Four braces made from 1/2-in. pipe connect each spoke and seat to the flange on the center pipe. An extra wheel 18 in. in diameter is fitted in between two seats and used as the propelling wheel. This wheel has bicycle cranks and pedals and carries a seat or a hobby horse. The four seats are fastened to the four pipes with 1/2-in. pipe clamps.



Small miniature electric lights are fastened to the overhead braces and supplied with electric current carried through wires to the swing by an ingenious device attached to the under side of the cast-iron ring or hub of the wheel. A ring of fiber on which two brass rings are attached is fastened to the hub and connections are made to the two rings through two brushes fastened to the post with a bracket. The wires run under the surface of the ground outside and connected to the source of electricity. The wires from the brass rings run through the center pipe to the top and are connected to the lamp sockets.



** Old-Time Magic-Part V [193]



** The Disappearing Coin [193]

This is an uncommon trick, entirely home-made and yet the results are as startling as in many of the professional tricks. A small baking-powder can is employed to vanish the coin, which should be marked by one of the audience for identification. Cut a slot in the bottom on the side of the can, as shown in Fig. 1. This slot should be just large enough for the coin that is used to pass through freely, and to have its lower edge on a level with the bottom of the can.

The nest or series of boxes in which the coin is afterwards found should consist of four small sized flat pasteboard boxes square or rectangular shaped and furnished with hinged covers. The smallest need be no larger than necessary to hold the coin and each succeeding box should be just large enough to hold the next smaller one which in turn contains the others.

A strip of tin about 1 by 1-3/4 in. is bent in the shape as shown in Fig. 2 to serve as a guide for the coin through the various boxes. This guide is inserted about 1/8 in. in the smallest box between the cover and the box and three rubber bands wrapped around the box as indicated. This box is then enclosed in the next larger box, the guide being allowed to project between the box and the cover, and the necessary tension is secured by three rubber bands around the box as before. In like manner the remaining boxes are



adjusted so that finally the prepared nest of boxes appears as in Fig. 3.

The coin can easily be passed into the inner box through the tin guide, then the guide can be withdrawn which permits the respective boxes to close and the rubber bands hold each one in a closed position.

The performer comes forward with the tin can in his right hand, the bottom of the can in his palm with the slot at the right side. He removes the cover with the left hand and passes his wand around the inner part of the can which is then turned upside down to prove that it contains nothing. The marked coin is dropped into the can by some one in the audience. The cover is replaced and the can shaken so the coin will rattle within. The shaking of the can is continued until the coin has slipped through the slot into his palm. The can is then placed on the table with his left hand. Then apparently he looks for something to cover the can. This is found to be a handkerchief which was previously prepared on another table concealing the nest of boxes. The coin in the right hand is quickly slipped into the guide of the nest of boxes, which was placed in an upright position, and the guide withdrawn, and dropped on the table. The performer, while doing this, is explaining that he is looking for a suitable cover for the can, but as he cannot find one he takes the handkerchief instead. The handkerchief is spread over the can and then he brings the nest of boxes. He explains how he will transfer the coin and passes his wand from the can to the boxes. The can is then shown to be empty and the boxes given to one in the audience to be opened. They will be greatly surprised to find the marked coin within the innermost box.



** How to Keep Film Negatives [194]

There are many devices for taking care of film negatives to keep them from curling and in a place easily accessible. Herewith is illustrated a method by which anyone can make a place for the negatives produced by his or her special film camera. The device is made up similar to a post card album with places cut through each leaf to admit each corner of the negatives. The leaves are made from white paper and when the negatives are in place the pictures made on them can



easily be seen through to the white paper background. These leaves can be made up in regular book form, or tied together similar to a loose-leaf book, thus adding only such pages as the negatives on hand will require. —Contributed by H. D. Harkins, St. Louis, Mo.



** Home-Made Match Safe [194]



Cut a piece of tin in the shape and with the dimensions shown in Fig. 1. Bend the saw-toothed edges at right angles to the piece on the dotted lines. Bend the part that is marked 5-1/2 in. in a half circle. Make a circle 3-1/2 in. in diameter on another piece of tin, cut out the circle and cut the disk in two as shown in Fig. 2. These half circle pieces are soldered to the sides of the teeth of the half circle made in the long piece of tin. Remove one end from the inside box containing matches and slip the back of the match safe through between the bottom of the inside box and the open end box that forms the cover. The matches will fall into the half circle tray at the lower end of the box which will be kept full of matches until they are all used from the box. —Contributed by C. F. White, Denver, Colo.



** An Electric Post Card Projector [195]

A post card projector is an instrument for projecting on a screen in a darkened room picture post cards or any other pictures of a similar size. The lantern differs from the ordinary magic lantern in two features; first, it requires no expensive condensing lens, and second, the objects to be projected have no need of being transparent.

Two electric globes are made to cast the strongest possible light on the picture card set between them and in front of which a lens is placed to project the view on the screen, the whole being enclosed in a light-tight box. The box can be made of selected oak or mahogany. The lens to be used as a projector will determine the size of the box to some extent. The measurements given in these instructions are for a lens of about 5 in. focal length. The box should be constructed of well seasoned wood and all joints made with care so they will be light-tight.

The portion shown carrying the lens in Fig. 1 is made to slide in the main body of the lantern for focusing. A box should first be made 5-1/2 in. wide, 5-1/2 in. high and 11 in. long. A hole is cut in the back of the box 4 by 6 in. represented by the dotted line in Fig. 2. This will be 3/4 in. from the top and bottom and 2-1/2 in. from each end of the outside of the box. Two strips of wood 1/2 in. wide and 6-1/2 in. long are fastened along the top and bottom of the back. The door covering this hole in the back, and, which is also used as a carrier for the post cards, is made from a board 4-1/2 in. wide and 6-1/2 in. long. The door is hinged to the lower strip and held in position by a turn button on the upper strip. The slides for the picture cards are made from strips of tin bent as shown, and tacked to the inside surface of the door.

The runners to hold the part carrying the lens are two pieces 2-1/4 in. wide by 5 in. long and should be placed



vertically, AA, as shown in Fig. 1, 3-1/2 in. from each end. An open space 4 in. wide and 5 in. high in the center is for the part carrying the lens to slide for focusing. The part carrying the lens is a shallow box 4 by 5 in. and 2 in. deep in the center of which a hole is cut to admit the lens. If a camera lens is used, the flange should be fastened with screws to the front part of this shallow box. The sides of this box should be made quite smooth and a good, but not tight, fit into the runners. Plumbago can be rubbed on to prevent sticking and to dull any rays of light.

Two keyless receptacles for electric globes are fastened to the under side of the top in the position shown and connected with wires from the outside. Two or three holes about 1 in. in diameter should be bored in the top between and in a line with the lights. These will provide ventilation to keep the pictures from being scorched or becoming buckled from the excessive heat. The holes must be covered over on the top with a piece of metal or wood to prevent the light from showing on the ceiling. This piece should not be more than 1/2 in. high and must



be colored dead black inside to cause no reflection.

The reflectors are made of sheet tin or nickel-plated metal bent to a curve as shown, and extending the whole height of the lantern. The length of these reflectors can be determined by the angle of the lens when covering the picture. This is clearly shown by the dotted lines in Fig. 1. The reflectors must not interfere with the light between the picture and the lens, but they must be sufficiently large to prevent any direct light reaching the lens from the lamps. In operation place the post card upside down in the slides and close the door. Sliding the shallow box carrying the lens will focus the picture on the screen.



** A Handy Calendar [196]



"Thirty days hath September, April, June and November," etc., and many other rhymes and devices are used to aid the memory to decide how many days are in each month of the year. Herewith is illustrated a very simple method to determine the number of days in any month. Place the first finger of your right hand on the first knuckle of your left hand, calling that knuckle January; then drop your finger into the depression between the first and second knuckles, calling this February; then the second knuckle will be March, and so on, until you reach July on the knuckle of the little finger, then begin over again with August on the first knuckle and continue until December is reached. Each month as it falls upon a knuckle will have 31 days and those down between the knuckles 30 days with the exception of February which has only 28 days. —Contributed by Chas. C. Bradley, West Toledo, Ohio.



** The Fuming of Oak [196]

Darkened oak always has a better appearance when fumed with ammonia. This process is rather a difficult one, as it requires an airtight case, but the description herewith given may be entered into with as large a case as the builder cares to construct.

Oak articles can be treated in a case made from a tin biscuit box, or any other metal receptacle of good proportions, provided it is airtight. The oak to be fumed is arranged in the box so the fumes will entirely surround the piece; the article may be propped up with small sticks, or suspended by a string. The chief point is to see that no part of the wood is covered up and that all surfaces are exposed to the fumes. A saucer of ammonia is placed in the bottom of the box, the lid or cover closed, and all joints sealed up by pasting heavy brown paper over them. Any leakage will be detected if the nose is placed near the tin and farther application of the paper will stop the holes. A hole may be cut in the cover and a piece of glass fitted in, taking care to have all the edges closed. The process may be watched through the glass and the article removed when the oak is fumed to the desired shade. Wood stained in this manner should not be French polished or varnished, but waxed.

The process of waxing is simple: Cut some beeswax into fine shreds and place them in a small pot or jar. Pour in a little turpentine, and set aside for half a day, giving it an occasional stir. The wax must be thoroughly dissolved and then more turpentine added until the preparation has the consistency of a thick cream. This can be applied to the wood with a rag and afterward brushed up with a stiff brush.



** How to Make an Electrolytic Rectifier [197]



Many devices which will change alternating current to a direct current have been put on the market, but probably there is not one of them which suits the amateur's needs and pocketbook better than the electrolytic rectifier.

For the construction of such a rectifier four 2-qt. fruit jars are required. In each place two electrodes, one of lead and one of aluminum. The immersed surface of the aluminum should be about 15 sq. in. and the lead 24 sq. in. The immersed surface of the lead being greater than that of the aluminum, the lead will have to be crimped as shown in Fig, 1. In both Fig. 1 and 2, the lead is indicated by L and the aluminum by A.

The solution with which each jar is to be filled consists of the following:

Water 2 qt. Sodium Carbonate 2 tablespoonfuls Alum 3 tablespoonfuls

Care should be taken to leave the connections made as shown in Fig. 2. The alternating current comes in on the wires as shown, and the direct current is taken from the point indicated.

The capacity of this rectifier is from 3 to 5 amperes, which is sufficient for charging small storage batteries, running small motors and lighting small lamps. —Contributed by J. H. Crawford, Schenectady, N. Y.



** The Rolling Marble [197]

Take a marble and place it on a smooth surface, The top of a table will do. Ask someone to cross their first and second fingers and place them on the marble as shown in the illustration. Then have the person roll the marble about and at the same time close the eyes or look in another direction. The person will imagine that there are two marbles instead of one.



** A Gas Cannon [197]

If you have a small cannon with a bore of 1 or 1-1/2 in., bore out the fuse hole large enough to tap and fit in a small sized spark plug such as used on a gasoline engine. Fill the cannon with gas from a gas jet and then push a



cork in the bore close up to the spark plug. Connect one of the wires from a battery to a spark coil and then to the spark plug. Attach the other wire to the cannon near the spark plug. Turn the switch to make a spark and a loud report will follow. —Contributed by Cyril Tegner, Cleveland, O.



** Old-Time Magic-Part VI [198]



** A Handkerchief Mended after Being Cut and Torn

Two persons are requested to come forward from the audience to hold the four corners of a handkerchief. Then beg several other handkerchiefs from the audience and place them on the one held by the two persons. When several handkerchiefs have been accumulated, have some one person draw out one from the bunch and examine for any marks that will determine that this handkerchief is the one to be mended after being mutilated. He, as well as others, are to cut off pieces from this handkerchief and to finally tear it to pieces.

The pieces are then all collected and some magic spirits thrown over the torn and cut parts; tie them in a small package with a ribbon and put them under a glass, which you warm with your hands. After a few seconds' time, you remove the glass, as you have held it all the time, and take the handkerchief and unfold it; everyone will recognize the mark and be amazed not to find a cut or tear in the texture.

This trick is very simple. You have an understanding with some one in the company, who has two handkerchiefs exactly alike and has given one of them to a person behind the curtain; he throws the other, at the time of request for handkerchiefs, on the handkerchiefs held for use in the performance of the trick. You manage to keep this handkerchief where it will be picked out in preference to the others, although pretending to thoroughly mix them up. The person selected to pick out a handkerchief naturally will take the handiest one. Be sure that this is the right one.

When the handkerchief has been torn and folded, put it under the glass, on a table, near a partition or curtain. The table should be made with a hole cut through the top and a small trap door fitted snugly in the hole, so it will appear to be a part of the table top. This trap door is hinged on the under side and opens into the drawer of the table and can be operated by the person behind the curtain who will remove the torn handkerchief and replace it with the good one and then close the trap door by reaching through the drawer of the table.



** The Magic Knot [198]

This is a very amusing trick which consists of tying one knot with two ends of a handkerchief, and pulling the



ends only to untie them again. Take the two diagonal corners of a handkerchief, one in each hand and throw the main part of the handkerchief over the wrist of the left hand and tie the knot as shown in the illustration. Pull the ends quickly, allowing the loop over the left hand to slip freely, and you will have the handkerchief without any knot.



** A Good Mouse Trap [198]

When opening a tomato or other small can, cut the cover crossways from side to side making four triangular pieces in the top. Bend the four ends outward and remove the contents, wash clean and dry and then bend the four ends inward, leaving a hole about 3/4 in. in diameter in the center. Drop in a piece of bread and lay the can down upon its side and the trap is ready for use. The mouse can get in but he cannot get out. —Contributed by E. J. Crocker, Victor, Colo.



** Finishing Aluminum [198]

Rubbing the surface of an aluminum plate with a steel brush will produce a satin finish.



** How to Make a Sailing Canoe [199]

A canvas canoe is easily made and light to handle, but in making one, it must be remembered that the cloth will tear, if any snags are encountered. Therefore such a craft cannot be used in all waters, but by being careful at shores, it can be used as safely as an ordinary sailing canoe. Be sure to select the best materials and when complete cover the seams well with paint.



The materials necessary for the construction of a sailing canoe, as illustrated in the engraving, are as follows:

1 keelson, 1 in. by 8 in. by 15 ft., selected pine. 14 rib bands, 1 in. square by 16 ft., clear pine. 2 gunwales, 1 in. by 2 in. by 16 ft. 1 piece for forms and bow pieces, 1 in. by 12 in. by 10 ft. 4 outwales, 1/4 in. by 2 in. by 16 ft. 1 piece, 3 in. wide and 12 ft. long, for cockpit frame. 1 piece, 2 in. wide and 12 ft. long, for center deck braces. 11 yd. of 1-1/2-yd. wide 12-oz. ducking. 8 yd. of 1-yd. wide unbleached muslin. 50 ft. of rope. 1 mast, 9 ft. long. Paint, screws and cleats.

The keelson, Fig. 1, is 14 ft. long, 8 in. wide in the center and tapered down from a point 4 ft. from each end to 1 in. at the ends. Both ends are mortised, one 6 in. for the stern piece, and the other 12 in. for the bow. Be sure to get the bow and stern pieces directly in the middle of the keelson and at right angles with the top edge. The stern and bow pieces are cut as shown in Fig. 2 and braced with an iron band, 1/8 in. thick and 3/4 in. wide, drilled and fastened with screws.

Study the sketches showing the details well before starting to cut out the pieces. Then there will be no trouble experienced later in putting the parts together. See that all the pieces fit their places as the work proceeds and apply the canvas with care.

Two forms are made as shown in Figs. 3 and 4; the smaller is placed 3 ft. from the bow and the large one, 7 ft. 3 in. from the stern. The larger mould is used temporarily while making the boat, and is removed after the ribs are in place. The gunwales are now placed over the forms and in the notches shown, and fastened with screws, and, after cutting the ends to fit the bow and stern pieces, they are fastened with bolts put through the three pieces. The sharp edges on one side of each rib-band are removed and seven of them fastened with screws to each side of the moulds, spacing them on the large mould 4 in. apart. The ribs are made of 28 good barrel hoops



which should be well soaked in water for several hours before bending them in shape. These are put in 6 in. apart and are fastened to the rib-bands with 7/8-in. wood screws. The ribs should be put in straight and true to keep them from pulling the rib-bands out of shape. After the ribs are in place and fastened to the rib-bands, gunwales and keelson, put on the outwale strips and fasten them to the gunwales between every rib with 1-1/2-in. screws.

Before making the deck, a block for the mast to rest in must be made and fastened to the keelson. This block, Fig. 5, is a cube having sides 6 in. square and is kept from splitting by an iron band tightly fitted around the outside. The block is fastened to the keelson, 3-1/2 ft. from the bow, with bolts through countersunk holes from the under side.

There are three deck braces made as shown in Figs. 6, 7 and 8. Braces, Figs. 6 and 7, form the ends of the cockpit which is 20 in. wide. A 6-in. board is fitted into the mortises shown in these pieces; a center piece is fitted in the other mortises. The other deck braces slope down from the center piece and are placed 6 in. apart. They are 1 in. square and are mortised into the center piece and fastened to the gunwales with screws. The main deck braces are fastened to the gunwales with 4-in. corner braces and to the center piece with 2-in. corner braces. The mast hole on the deck is made as follows: Secure a piece of pine 1 in. thick, 6 in. wide and 3 ft. long. Cut this in halves and mortise for the center piece in the two halves and fasten to the gunwales. A block of pine, 4 in. thick and 12 in. long, is cut to fit under the top boards, Fig. 9, and fastened to them with bolts. With an expansive bit bore a hole 3 in. in diameter through the block. Be sure to get the block and hole directly over the block that is fastened to the keelson. Put on a coat of boiled linseed oil all over the frame before proceeding farther.

Putting on the canvas may be a difficult piece of work to do, yet if the following simple directions are followed out no trouble will be encountered. The 11-yd. length of canvas is cut in the center, doubled, and a seam made joining the two pieces together. Fill the seam with thick paint and tack it down with copper tacks along the center of the keelson. When this is well tacked commence stretching and pulling the canvas in the middle of the gunwales so as to make it as even and tight as possible and work toward each end, tacking the canvas as it is stretched to the outside of the gunwale. Seam the canvas along the stern and bow pieces as was done on the keelson. The deck is not so hard to do, but be careful to get the canvas tight and even. A seam should be made along the center piece. The trimming is wood, 1/4 in. thick and 1/2 in. wide. A strip of this is nailed along the center piece over the canvas. The outwales are nailed on over the canvas. A piece of oak, 1 in. thick 1-1/2 in. wide and 14 in. long, is fastened with screws over the canvas on the stern piece; also, a piece 1/4 in. thick, 1 in. wide and 24 in. long is well soaked in water, bent to the right shape and fastened over the canvas on the bow.

The rudder is made as shown in Fig. 10 with a movable handle. A strip 1 in. thick by 2 in. wide, is bolted to the keelson over the canvas for the outer keel. The keel, Fig. 11, is 6 in. wide at one end and 12 in. at the other, which is fastened to the outer keel with bolts having thumb nuts. The mast can be made of a young spruce tree having a diameter of 3 in. at the base with sufficient height to make it 9 ft. long. The canoe is driven by a lanteen sail and two curtain poles, each 1 in. in diameter and 10 ft. long, are used for the boom and gaff, which are held together with two pieces of iron bent as shown in Fig. 12. The sail is a triangle, 9-3/4 by 9-3/4 by 8-1/2 ft. which is held to the boom and gaff by cord lacings run through eyelets inserted in the muslin. The eyelets are of brass placed 4 in. apart in the muslin. The mast has two side and one front stay, each fitted with a turnbuckle for tightening. A pulley is placed at the top and bottom of the mast for the lift rope. The sail is held to the mast by an iron ring and the lift rope at the top of the mast. The boom rope is held in the hand and several cleats should be placed in the cockpit for convenience. A chock is placed at the bow for tying up to piers. Several coats of good paint complete the boat. —Contributed by O. E. Tronnes, Wilmette, Ill.



** A Home-Made Hand Vise [201]

A very useful little hand vise can easily be made from a hinge and a bolt carrying a wing nut. Get a fast



joint hinge about 2 in. or more long and a bolt about 1/2 in. long that will fit the holes in the hinge. Put the bolt through the middle hole of the hinge and replace the nut as shown in the drawing. With this device any small object may be firmly held by simply placing it between the sides of the hinge and tightening the nut.



** Proper Design for a Bird House [201]

This bird house was designed and built to make a home for the American martin. The house will accommodate 20 families. All the holes are arranged so they will not be open to the cold winds from the north which often kill the birds which come in the early spring. Around each opening is an extra ring of wood to make a longer passage which assists the martin inside in fighting off the English



sparrow who tries to drive him out. The holes are made oval to allow all the little ones to get their heads out for fresh air. The long overhanging eaves protect the little birds from the hot summer sun. The rooms are made up with partitions on the inside so each opening will have a room. The inside of the rooms should be stained black.



** Boomerangs and How to Make Them [202]

A boomerang is a weapon invented and used by the native Australians, who seemed to have the least intelligence of any race of mankind. The



boomerang is a curved stick of hardwood, Fig. 1, about 5/16 in. thick, 2-1/2 in. wide and 2 ft. long, flat on one side, with the ends and the other side rounding. One end of the stick is grasped in one hand with the convex edge forward and the flat side up and thrown upward. After going some distance and ascending slowly to a great height in the air with a quick rotary motion, it suddenly returns in an elliptical orbit to a spot near the starting point. If thrown down on the ground the boomerang rebounds in a straight line, pursuing a ricochet motion until the object is struck at which it was thrown.

Two other types of boomerangs are illustrated herewith and they can be made as described. The materials necessary for the T-shaped boomerang are: One piece of hard maple 5/16 in. thick, 2-1/2 in. wide, and 3 ft. long; five 1/2-in. flat-headed screws. Cut the piece of hard maple into two pieces, one 11-1/2 in. and the other 18 in. long. The corners are cut from these pieces as shown in Fig. 2, taking care to cut exactly the same amount from each corner. Bevel both sides of the pieces, making the edges very thin so they will cut the air better. Find the exact center of the long piece and make a line 1-1/4 in. on each side of the center and fasten the short length between the lines with the screws as shown in Fig. 3. The short piece should be fastened perfectly square and at right angles to the long one.

The materials necessary for the cross-shaped boomerang are one piece hard maple 5/16 in. thick, 2 in. wide and 30 in. long and five 1/2-in. flat headed screws. Cut the maple- into two 14-in. pieces and plane the edges of these pieces so the ends will be 1-1/2 in. wide, as shown in Fig. 4. Bevel these pieces the same as the ones for the T-shaped boomerang. The two pieces are fastened together as shown in Fig. 5. All of the boomerangs when completed should be given several coats of linseed oil and thoroughly dried. This will keep the wood from absorbing water and becoming heavy. The last two boomerangs are thrown in a similar way to the first one, except that one of the pieces is grasped in the hand and the throw given with a quick underhand motion. A little practice is all that is necessary for one to become skillful in throwing them. —Contributed by O. E. Tronnes, Wilmette, Ill.



** How to Make Water Wings [202]

Purchase a piece of unbleached muslin, 1 yd. square. Take this and fold it over once, forming a double piece 1-1/2 ft. wide and 3 ft. long. Make a double stitch all around the edge, leaving a small opening at one corner. Insert a piece of tape at this corner to be used for tying around the opening when the bag is blown up. The bag is then turned inside out, soaked with water and blown up. An occasional wetting all over will prevent it from leaking. As these wings are very large they will prevent the swimmer from sinking. —Contributed by W. C. Bliss, St. Louis, Mo.



** How to Make an Ammeter [203]

The outside case of this instrument is made of wood taken from old cigar boxes with the exception of the back. If carefully and neatly made, the finished instrument will be very satisfactory. The measurements here given need not be strictly followed out, but can be governed by circumstances. The case should first be made and varnished and while this is drying, the mechanical parts can be put together.



The back is a board 3/8 in. thick, 6-1/2 in. wide and 6-3/4 in. long. The outer edges of this board are chamfered. The other parts of the case are made from the cigar box wood which should be well sandpapered to remove the labels. The sides are 3-1/4 in. wide and 5 in. long; the top and bottom, 3-1/4 in. wide and 4-1/2 in. long. Glue a three cornered piece, A, Fig. 1, at each end on the surface that is to be the inside of the top and bottom pieces. After the glue, is set, fasten the sides to the pieces with glue, and take care that the pieces are all square. When the glue is set, this square box is well sandpapered, then centered, and fastened to the back with small screws turned into each three-cornered piece.

The front, which is a piece 5-1/4 in. wide and 6-1/2 in. long, has a circular opening cut near the top through which the graduated scale may be seen. This front is centered and fastened the same as the back, and the four outside edges, as well as the edges around the opening, are rounded. The whole case can now be cleaned and stained with a light mahogany stain and varnished. Cut another piece of board, B, Figs. 2 and 3, to just fit inside the case and rest on the ends of the three-cornered pieces, A, and glue to this board two smaller pieces, C, 3 in. square, with the grain of the wood in alternate directions to prevent warping. All of these pieces are made of the cigar box wood. Another piece, D, 3/8 in. thick and 3 in. square, is placed on the other pieces and a U-shaped opening 1-3/4 in. wide and 2-1/2 in. high sawed out from all of the pieces as shown. The piece D is attached to the pieces C with four 1/2-in. pieces 2-5/8 in. long.

A magnet is made from a soft piece of iron, E, about 3/8 in. thick, 1-1/4 in. wide and 2-3/4 in. long. Solder across each end of the iron a piece of brass wire, F, and make a turn in each end of the wires, forming an eye for a screw. These wires are about 2-1/2 in. long. Wind three layers of about No. 14 double cotton-covered copper wire on the soft iron and leave about 5 or 6 in. of each end unwound for connections.

The pointer is made as shown in Fig. 5 from 1/16-in. brass wire filed to make a point at both ends for a spindle. About 1/2 in. from each end of this wire are soldered two smaller brass wires which in turn are soldered to a strip of light tin 1/4 in. wide and 2-5/8 in. long. The lower edge of this tin should be about 1/2 in. from the spindle. The pointer is soldered to the spindle 1/4 in. from one end. All of these parts should be brass with the exception of the strip of tin. Another strip of tin, the same size as the first, is soldered to two brass wires as shown in Fig. 4. These wires should be about 1 in. long.

The spindle of the pointer swings freely between two bars of brass, G, 1/16 in. thick, 1/4 in. wide and 2-1/2 in. long. A small hole is countersunk in one of the bars to receive one end of the spindle and a hole 1/8 in. in diameter is drilled in the other and a thumb nut taken from the binding-post of an old battery soldered over the hole so the screw will pass through when turned into the nut. The end of the screw is countersunk to receive the other end of the spindle. A lock nut is necessary to fasten the screw when proper adjustment is secured. A hole is drilled in both ends of the bars for screws to fasten them in place. The bar with the adjusting screw is fastened on the back so it can be readily adjusted through the hole H, bored in the back. The pointer is bent so it will pass through the U-shaped cut-out and up back of the board B. A brass pin is driven in the board B to hold the pointer from dropping down too far to the left. Place the tin, Fig. 4, so it will just clear the tin, Fig. 5, and fasten in place. The magnet is next placed with the ends of the coil to the back and the top just clearing the tin strips. Two binding screws are fitted to the bottom of the back and connected to the extending wires from the coil.

The instrument is now ready for calibrating. This is done by connecting it in series with another standard ammeter which has the scale marked in known quantities. In this series is also connected a variable resistance and a battery or some other source of current supply. The resistance is now adjusted to show .5 ampere on the standard ammeter and the position of the pointer marked on the scale. Change your resistance to all points and make the numbers until the entire scale is complete.

When the current flows through the coil, the two tinned strips of metal are magnetized, and being magnetized by the same lines of force they are both of the same polarity. Like poles repel each other, and as the part Fig. 4 is not movable, the part carrying the pointer moves away. The stronger the current, the greater the magnetism of the metal strips, and the farther apart they will be forced, showing a greater defection of the pointer. —Contributed by George Heimroth, Richmond Hill, L. I.



** How to Make an Equatorial [204] Condensed from article contributed by J. R. Chapman, F.R.A.S. Austwick Hall. W. Yorkshire. England

This star finder can easily be made by anyone who can use a few tools as the parts are all wood and the only lathe work necessary is the turned shoulder on the polar axis and this could be dressed and sandpapered true enough for the purpose. The base is a board 5 in. wide and 9 in. long which is fitted with an ordinary wood screw in each corner for leveling. Two side pieces cut with an angle equal to the colatitude of the place are nailed to the base and on top of them is fastened another board on which is marked the hour circle as shown. The end of the polar axis B, that has the end turned with a shoulder, is fitted in a hole bored in the center of the hour circle. The polar axis B is secured to the board with a wooden collar and a pin underneath. The upper end of the polar axis is fitted with a 1/4-in. board, C, 5-1/2 in. in diameter. A thin compass card divided into degrees is fitted on the edge of this disk for the declination circle.

The hour circle A is half of a similar card with the hour marks divided into 20 minutes. An index pointer is fastened to the base of the polar axis. A pointer 12 in. long is fastened with a small bolt to the center of the declination circle. A small opening is made in the pointer into which an ordinary needle is inserted. This needle is adjusted to the degree to set the pointer in declination and when set, the pointer is clamped with the bolt at the center. A brass tube having a 1/4-in. hole is fastened to the pointer.

The first thing to do is to get a true N and S meridian mark. This can be approximately obtained by a good compass, and allowance made for the magnetic declination at your own place. Secure a slab of stone or some other solid flat surface, level this and have it firmly fixed facing due south with a line drawn through the center and put the equatorial on the surface with XII on the south end of the line. Then set the pointer D to the declination of the object, say Venus at the date of observation. You now want to know if this planet is east or west of your meridian at the time of observation. The following formula will show how this may be found. To find a celestial object by equatorial: Find the planet Venus May 21, 1881, at 9 hr. 10 min. A. M. Subtract right ascension of planet from the time shown by the clock, thus:

hour minute second 9 hr. 10 min. shows mean siderial. 1 0 0 Add 12 hrs 12 —- —- —- 13

Right ascension of Venus 2 10 —- —- —- Set hour circle to before meridian 10 50 0 Again————————— At 1 hr. 30 min. mean clock shows 5 20 0 Right ascension of Venus 2 10 0 —- —- —- Set hour circle to 3 10 0

Books may be found in libraries that will give the right ascension and declination of most of the heavenly bodies.

The foregoing tables assume that you have a clock rated to siderial time,



but this is not absolutely necessary. If you can obtain the planet's declination on the day of observation and ascertain when it is due south, all you have to do is to set the pointer D by the needle point and note whether Venus has passed your meridian or not and set your hour index. There will be no difficulty in picking up Venus even in bright sunlight when the plant is visible to the naked eye.



** Electric Light Turned On and Off from Different Places [205]

How nice it would be to have an electric light at the turn in a stairway, or at the top that could be turned on before starting up the stair and on reaching the top turned out, and vice



versa when coming down. The wiring diagram as shown in the illustration will make this a pleasant reality. This wiring may be applied in numerous like instances. The electric globe may be located at any desired place and the two point switches are connected in series with the source of current as shown in the sketch. The light may be turned on or off at either one of the switches. —Contributed by Robert W. Hall, New Haven, Conn.



** How to Make a Bunsen Cell [206]

This kind of a cell produces a high e.m.f. owing to the low internal resistance. Procure a glass jar such as used for a gravity battery, or, if one of these cannot be had, get a glazed vessel of similar construction. Take a piece of sheet zinc large enough so that when it is rolled up in the shape of a cylinder it will clear the edge of the jar by about 1/2 in. Solder a wire or binding-post to the edge of the cylinder for a connection.



Secure a small unglazed vessel to fit inside of the zinc, or such a receptacle as used in a sal ammoniac cell, and fill it with a strong solution of nitric acid. Fill the outer jar with a solution of 16 parts water and 5 parts sulphuric acid. The connections are made from the zinc and carbon.



** Optical Illusion [206]

Can you tell which of these three figures is the tallest? Make a guess, and then verify its correctness by measurement.



** One Way to Cook Fish [206]

One of the best and easiest ways of cooking fish while out camping is told by a correspondent of Forest and Stream. A fire is built the size for the amount of food to be cooked and the wood allowed to burn down to a glowing mass of coals and ashes. Wash and season your fish well and then wrap them up in clean, fresh grass, leaves or bark. Then, after scraping away the greater part of the coals, put the fish among the ashes, cover up with the same, and heap the glowing coals on top. The fish cooks quickly—15 or 20 minutes—according to their size.

If you eat fish or game cooked after this fashion you will agree that it cannot be beaten by any method known to camp culinary savants. Clay also answers the purpose of protecting. the fish or game from the fire if no other material is at hand, and for anything that requires more time for cooking it makes the best covering. Wet paper will answer, especially for cooking fish.



** Hardening Copper [206]

A successful method of hardening copper is to add 1 lb. of alum and 4 oz. arsenic to every 20 lb. of melted copper and stir for 10 minutes.



** Packing Cut from Felt Hats [206]

Felt from an old hat makes good packing for automobile water-circulating pumps. Strips should be cut to fit snugly in the stuffing box. When the follower is screwed down, it will expand the felt and make a watertight joint.



** Homemade Gasoline Engine [206]

The material used in the construction of the gasoline engine, as shown in the accompanying picture, was pieces found in a scrap pile that usually occupies a fence corner on almost every farm. The cylinder consists of



an old pump cylinder, 3/8 in. thick, 1-3/4 in. inside diameter and about 5 in. long. This was fastened between some wooden blocks which were bolted on the tool carriage of a lathe and then bored out to a diameter of about 2 in. The boring bar, Fig. 1, consisted of an old shaft with a hole bored through the center and a tool inserted and held for each cut by a setscrew. A wood mandrel with a metal shaft to turn in the centers of a lathe was made to fit the bored-out cylinder. The cylinder was then placed on the mandrel, fastened with a pin, and threaded on both ends. Flanges were next made from couplings discarded from an old horsepower tumbling rod, to fit on the threaded ends of the cylinder casting. When these flanges were tightly screwed on the casting and faced off smooth the whole presented the appearance of a large spool.

The back cylinder head was made from a piece of cast iron, about 1/2 in. thick, turned to the same diameter as the flanges, and with a small projection to fit snugly inside the cylinder bore. Two holes were then drilled in this head and tapped for 3/4-in. pipe. Two pieces of 3/4 -in. pipe were fitted to these holes so that, when they were turned in, a small part of the end of each pipe projected on the inside of the cylinder head. These pieces of pipe serve as valve cages and are reamed out on the inside ends to form a valve seat. The outlet for the exhaust and the inlet for the gas and air are through holes drilled in the side of each pipe respectively and tapped for 1/2-in. pipe. Two heads were then made to fit over the outer ends of the valve cages. These heads looked similar to a thread spool with one flange cut off, the remaining flange fitting on the



end of the valve cage and the center extending down inside to make a long guide for the valve stems. These heads are held in place by a wrought-iron plate and two bolts, one of which is plainly shown in the picture. This plate also supports the rocker arms, Fig. 2, and the guides for the rods that operate the valves. Both valves are mechanically operated by one cam attached to a shaft running one turn to two of the crankshaft. The gears to run this shaft were cut from solid pieces on a small home-made gear-cutting attachment for the lathe as shown in Fig. 3. The gear on the crankshaft has 20 teeth meshing into a 40-tooth gear on the cam shaft.

The main part of the frame consists of a piece of 1/2-in. square iron, 30 in. long, bent in the shape of a U, and on the outside of this piece is riveted a bent piece of sheet metal 1/8 in. thick and 3 in. wide. The U-shaped iron is placed near one edge of the sheet metal. Two pieces of 2-1/2-in. angle iron are riveted vertically on the ends of the U-shaped iron and a plate riveted on them to close the open end and to form a face on which to attach the cylinder with bolts or cap screws. A hole was cut through the angle irons and plate the same size as the bore of the cylinder so the piston could be taken out without removing the cylinder. A 1-in. angle iron was riveted to one side of the finished frame to make a support for the crankshaft bearing. The rough frame, Fig. 4, was then finished on an emery wheel. This long frame had to be made to accommodate the crosshead which was necessary for such a short cylinder.

The piston and rod were screwed together and turned in one operation on a lathe. The three rings were made from an old cast-iron pulley. The cap screws were made from steel pump rods. A piece of this rod was centered in a lathe and turned so as to shape six or more screws, Fig. 5, then removed and the first one threaded and cut off, then the second and so on until all of them were made into screws. The rod was held in a vise for this last operation. Studs were made by threading both ends of a proper length rod. Make-and-break ignition is used on the engine; however, a jump spark would be much better. The flywheel and mixing valve were purchased from a house dealing in these parts. The water jacket on the cylinder is a sheet of copper formed and soldered in place, and brass bands put on to co v e r the soldered joints. —Contributed by Peter Johnson, Clermont, Iowa.