The Boy Mechanic Volume I 700 Things For Boys To Do (part 2)

A room from which all light may be excluded and a window through which the light can enter without obstruction from trees or nearby buildings, with a shelf to hold the camera and a table with an upright drawing-board attached, complete the arrangement. The back is taken out of the camera and fitted close against the back of the shelf, which must be provided with a hole the same size and shape as the opening in the back of the camera. The negative used to make the enlarged print is placed in the shelf at A, Fig. 1. The rays of the clear, unobstructed light strike the mirror, B, and reflect through the negative, A, through the lens of the camera and on the board, as shown in Fig. 2. The window must be darkened all around the shelf.

After placing the negative and focusing the lens for a clear image on the board, the shutter is set and a bromide paper is placed on the board. The paper is exposed, developed and fixed by the directions that are enclosed in the package of bromide papers.

Positioning A Hanging Lamp

Don't pull a lamp hung by flexible cord to one side with a wire and then fasten to a gas pipe. I have seen a wire become red hot in this manner. If the lamp hung by a cord must be pulled over, use a string.

A Curious Compressed Air Phenomenon

Push a pin through an ordinary business card and place the card against one end of a spool with the pin inside the bore, as shown in the sketch. Then blow through the spool, and it will be found that the card will not be blown away, but will remain suspended without any visible support. This phenomenon is explained by the fact that the air radiates from the center at a velocity which is nearly constant, thereby producing a partial vacuum between the spool and the card. Can the reader devise a practical application of this contrivance?

Simple Switch for Reversing a Current

Take two strips of copper or brass and fasten them together by means of gutta-percha (Fig. 1); also provide them with a handle. Saw out a rectangular block about one and one-half times as long as the brass strips and fasten to it at each end two forked pieces of copper or brass, as in Fig. 2. Fasten on the switch lever, as at A and B, Fig. 2, so that it can rotate about these points. Connect the wires as shown in Fig. 3. To reverse, throw the lever from one end of the block to the other.

Contributed by R. L. Thomas, San Marcos, Tex.

Novel Mousetrap

A piece of an old bicycle tire and a glass fruit jar are the only materials required for making this trap. Push one end of the tire into the hole, making sure that there is a space left at the end so that the mice can get in. Then bend the other end down into a fruit jar or other glass jar. Bait may be placed in the jar if desired, although this is not necessary.

Contributed by Geo. G. McVicker, North Bend, Neb.

Polishing Nickel

A brilliant polish may be given to tarnished nickel by immersing in alcohol and 2 per cent of sulphuric acid from 5 to 15 seconds. Take out, wash in running water, rinse in alcohol, and rub dry with linen cloth.

Homemade Arc Light

By rewinding an electric-bell magnet with No. 16 wire and connecting it in series with two electric-light carbons, as shown in the sketch, a small arc will be formed between the carbon points when the current is applied. In the sketch, A is the electric-bell magnet; B, the armature; C C, carbon sockets; D, carbons, and E E, binding posts. When connected with 10 or 12 dry batteries this lamp gives a fairly good light.

Contributed by Morris L. Levy, San Antonio, Tex.

Lighting an Incandescent Lamp with an Induction Coil

An incandescent lamp of low candlepower may be illuminated by connecting to an induction coil in the manner shown in the sketch. One wire is connected to the metal cap of the lamp and the other wire is fastened to the glass tip. If the apparatus is then placed in the dark and the current turned on, a peculiar phosphorescent glow will fill the whole interior of the lamp. The induction coil used for this purpose should give a spark about 1/2 in. long or more.

Contributed by Joseph B. Bell, Brooklyn.

How to Make a Jump-Spark Coil

The induction coil is probably the most popular piece of apparatus in the electrical laboratory, and particularly is it popular because of its use in experimental wireless telegraphy. Ten years ago wireless telegraphy was a dream of scientists; today it is the plaything of school-boys and thousands of grown-up boys as well.

Divested of nearly all technical phrases, an induction coil may be briefly described as a step-up transformer of small capacity. It comprises a core consisting of a cylindrical bundle of soft-iron wires cut to proper length. By means of two or more layers of No. 14 or No. 16 magnet wire, wound evenly about this core, the bundle becomes magnetized when the wire terminals are connected to a source of electricity.

Should we now slip over this electromagnet a paper tube upon which has been wound with regularity a great and continuous length of No. 36 magnet wire, it will be found that the lines of force emanating from the energized core penetrate the new coil-winding almost as though it were but a part of the surrounding air itself, and when the battery current is broken rapidly a second electrical current is said to be induced into the second coil or secondary.

All or any of the parts of an induction coil may be purchased ready-made, and the first thing to do is to decide which of the parts the amateur mechanic can make and which would be better to buy ready-made. If the builder has had no experience in coil-winding it would probably pay to purchase the secondary coil ready-wound, as the operation of winding a mile or more of fine wire is very difficult and tedious, and the results are often unsatisfactory. In ordering the secondary it is always necessary to specify the length of spark desired.

The following method of completing a 1-in. coil illustrates the general details of the work. The same methods and circuits apply to small and larger coils. The ready-made secondary is in solid cylindrical form, about 6 in. long and 2-5/8 in. diameter, with a hole through the winding 1-1/4 in. in diameter, as shown in Fig. 1. The secondary will stand considerable handling without fear of injury, and need not be set into a case until the primary is completed. The primary is made of fine annealed No. 24 iron wire cut 7 in. or 8 in. in length, as the maker prefers, and bundled to a diameter of 7/8 in. The wires may be straightened by rolling two or three at a time between two pieces of hard wood. If the amateur has difficulty in procuring this wire, the entire core may be purchased ready-made.

After the core wires are bundled, the core is wrapped with one or two layers of manila paper. The straighter the wire the more iron will enter into the construction of the core, which is desirable. Beginning half an inch from one end, No. 16 cotton-covered magnet wire is wound from one end to the other evenly and then returned, making two layers, and the terminals tied down to the core with twine. Core and primary are then immersed in boiling paraffine wax to which a small quantity of resin and beeswax has been added. This same wax may be used later in sealing the completed coil into a box. Over this primary is now wrapped one layer of okonite tape, or same thickness of heavily shellacked muslin. This completed primary will now allow of slipping into the hole in the secondary.

Should the secondary have been purchased without a case, a wooden box of mahogany or oak is made, large enough to contain the secondary and with an inch to spare all around, with room also for a small condenser; but if it is not convenient to do this work, a box like that shown in Fig. 2 may be purchased at a small cost. A 7/8-in. hole is bored in the center of one end, through which the primary core projects 1/8 in. This core is to be used to attract magnetically the iron head of a vibrating interrupter, which is an important factor of the coil. This interrupter is shaped as in Fig. 4, and is fastened to the box in such a way that the vibrator hammer plays in front of the core and also that soldered connections may be made inside the box with the screws used in affixing the vibrator parts to the box. The condenser is made of four strips of thin paper, 2 yd. long and 5 in. wide, and a sufficient quantity of tinfoil. When cut and laid in one continuous length, each piece of tin-foil must overlap the adjoining piece a half inch, so as to form a continuous electrical circuit. In shaping the condenser, one piece of the paper is laid down, then the strip of tin-foil, then two strips of paper and another layer of foil, and finally the fourth strip of paper. This makes a condenser which may be folded, beginning at one end and bending about 6 in. at a time. The condenser is next wrapped securely with bands of paper or tape, and boiled in pure paraffine wax for one hour, after which it is pressed under considerable weight until firm and hard. One of the sheets of tin-foil is to form one pole of the condenser, and the other sheet, which is insulated from the first, forms the other pole or terminal. (This condenser material is purchasable in long strips, ready for assembling.)

The wiring diagram, Fig. 3, shows how the connections are made. This method of connecting is suitable for all coils up to 1-1/2 in. spark, but for larger coil better results will be obtained by using an independent type of interrupter, in which a separate magnet is used to interrupt the circuit. Besides the magnetic vibrators there are several other types, such as the mercury dash-pot and rotary-commutator types, but these will become better known to the amateur as he proceeds in his work and becomes more experienced in coil operation.

Combined Door Bell and Electric Alarm

This device consists of a battery and bell connection to an alarm clock which also acts as a door bell, the whole being mounted on a board 18 in. long and 12 in. wide.

Referring to the sketch accompanying this article, the letters indicate as follows: A, bell; B, battery ; C, switch; D, V-shaped copper strip; E, copper lever with 1-in. flange turned on one side, whole length, 4 in.; F, spring to throw lever E down in V-shaped piece to make connection; G, lever to hold out E when device is used as a door bell; lines H, go, one from bell, A, and one from battery, B, to the door; I, shelf for clock.

See that the ring in the alarm key of the clock works easily, so that when it is square across the clock it will drop down. Fasten a piece of copper about 1 in. long to key, then wind the alarm just enough so that the key stands straight up and down. Place the clock on the shelf and the key under the flange of lever E. Pull lever G down out of the way and close the lever on the switch. The alarm key will turn and drop down, letting lever E drop into the V-shaped piece D and make connection.

For the door-bell connection close lever on switch C, and put G up so that D and E do not come in contact. If anyone is ill and you do not want the bell to ring, open switch C.

The wiring for this device may all be on the back of the board. The switch and levers are fastened with small screw bolts, which allows wiring at the back. Saw two spools in half and fasten the halves to the four corners of the board at the back, and the apparatus may be put up where one likes.

To Build a Small Brass Furnace

Bend a piece of stout sheet iron 23 in. by 12 in. round so that the inside diameter is 7 in., and then rivet the seam. Fit in a round piece of sheet iron for the bottom. Make a hole about the size of a shilling in the side, 2 in. from the bottom. This is for blowing.

Line the furnace, bottom and sides with fire-clay to a depth of 1/2 in. Use charcoal to burn and an ordinary bellows for blowing, says the Model Engineer, London. The best blast is obtained by holding the nozzle of the bellows about an inch from the hole, instead of close to it.

Avoid Paper Lamp Shades

Don't wrap paper around a lamp for a shade. You might go away and forget it and a fire might be started from the heat. Use a glass or metal shade. That is what they are for.

Why Gravity Batteries Fail to Work

Many amateur electricians and some professionals have had considerable trouble with gravity batteries. They follow directions carefully and then fail to get good results. The usual trouble is not with the battery itself, but with the circuit. A gravity battery is suitable only for a circuit which is normally closed. It is therefore undesirable for electric bells, induction coils and all other open-circuit apparatus. The circuit should also have a high resistance. This makes it impractical for running fan motors, as the motor would have to be wound with fine wire and it would then require a large number of batteries to give a sufficiently high voltage.

To set up a gravity battery: Use about 3-1/2 lb. of blue stone, or enough to cover the copper element 1 in. Pour in water sufficient to cover the zinc 1/2 in. Short-circuit for three hours, and the battery is ready for use. If desired for use immediately, do not short-circuit, but add 5 or 6 oz. of zinc sulphate.

Keep the dividing line between the blue and white liquids about 1/2 in. below the bottom of the zinc. If too low, siphon off some of the white liquid and add the same amount of water, but do not agitate or mix the two solutions. This type of battery will give about 0.9 of a volt, and should be used on a circuit of about 100 milli-amperes.

A Skidoo-Skidee Trick

In a recent issue of Popular Mechanics an article on "The Turning Card Puzzle" was described and illustrated. Outside of the scientific side involved, herein I describe a much better trick. About the time when the expression "skidoo" first began to be used I Invented the following trick and called it "Skidoo" and "Skidee," which created much merriment. Unless the trick is thoroughly understood, for some it will turn one way, for others the opposite way, while for others it will not revolve at all. One person whom I now recall became red in the face by shouting skidoo and skidee at it, but the thing would not move at all, and he finally from vexation threw the trick into the fire and a new one had to be made. Very few can make it turn both ways at will, and therein is the trick.

Take a piece of hardwood 3/8 in. square and about 9 in. long. On one of the edges cut a series of notches as indicated in Fig. 1. Then slightly taper the end marked B until it is nicely rounded as shown in Fig. 2. Next make an arm of a two-arm windmill such as boys make. Make a hole through the center of this one arm. Enlarge the hole slightly, enough to allow a common pin to hold the arm to the end B and not interfere with the revolving arm. Two or three of these arms may have to be made before one is secured that is of the exact proportions to catch the vibrations right.

To operate the trick, grip the stick firmly in one hand, and with the forward and backward motion of the other allow the first finger to slide along the top edge, the second finger along the side, and the thumb nail will then vibrate along the notches, thus making the arm revolve in one direction. To make the arm revolve in the opposite dlrection—keep the hand moving all the time, so the observer will not detect the change which the hand makes—allow the first finger to slide along the top, as in the other movement, the thumb and second finger changing places: e.g., In the first movement you scratch the notches with the thumb nail while the hand is going from the body, and in the second movement you scratch the notches with the nail of the second finger when the hand is coming toward the body, thus producing two different vibrations. In order to make it work perfectly (?) you must or course say "skidoo" when you begin the first movement, and then, no matter how fast the little arm is revolving when changed to the second movement you must say "skidee" and the arm will immediately stop and begin revolving in the opposite direction. By using the magic words the little arm will obey your commands instantly and your audience will be mystified. If any of your audience presume to dispute, or think they can do the same let them try it. You will no doubt be accused of blowing or drawing in your breath, and many other things in order to make the arm operate. At least it is amusing. Try it and see.

Contributed by Charles Clement Bradley, Toledo, Ohio.

Effects of Radium

Radium acts upon the chemical constituents of glass, porcelain and paper, imparting to them a violet tinge; changes white phosphorus to yellow, oxygen to ozone, affects photograph plates and produces many other curious chemical changes.

Naval Speed Record

On its official trial trip the British torpedo boat destroyer "Mohawk" attained the record speed of a little over 39 miles an hour.

How to Enlarge from Life in the Camera

Usually the amateur photographer gets to a point in his work where the miscellaneous taking of everything in sight is somewhat unsatisfying: There are many special fields he may enter, and one of them is photomicrography. It is usually understood that this branch of photography means an expensive apparatus. If the worker is not after too high a magnification, however, there is a very simple and effective means of making photomicrographs which requires no additional apparatus that cannot be easily and quickly constructed at home.

Reproduced with this article is a photograph of dandelion seeds—a magnification of nine diameters or eighty-one times. The apparatus which produced this photograph consisted of a camera of fairly long draw, a means for holding it vertical, a short-focus lens, and, if possible, but not essential, a means for focusing that lens in a minute manner. On top of the tripod is the folding arrangement, which is easily constructed at home with two hinged boards, an old tripod screw, an old bed plate from a camera for the screw to fit in, and two sliding brass pieces with sets crews that may be purchased from any hardware store under the name of desk sliding braces. To the front board is attached a box, carrying the lens and the bed of the sliding object carrier, which can be moved forward and back by the rack and pinion, that also can be obtained from hardware stores. If the bed for the object carrier be attached to the bed of the camera instead of to the front board, the object carrier need have no independent movement of its own, focusing being done by the front and back focus of the camera; but this is less satisfactory, particularly when accurate dimensions are to be determined, says the Photographic Times. This outfit need not be confined to seeds alone, but small flowers, earth, chemicals, insects, and the thousand and one little things of daily life—all make beautiful subjects for enlarged photographs. These cannot be made by taking an ordinary photograph and enlarging through a lantern. When a gelatine dry plate is magnified nine diameters, the grains of silver in the negative will be magnified also and produce a result that will not stand close examination. Photographs made by photomicrography can be examined like any other photographs and show no more texture than will any print.

Steel Pen Used in Draftsman's Ink Bottle Cork

A steel pen makes an ideal substitute for a quill in the stopper of the draftsman's ink bottle. The advantage of this substitute is that there is always one handy to replace a broken or lost pen, while it is not so with the quill.

Contributed by George C. Madison, Boston, Mass.

How to Make a Pilot Balloon By E. Goddard Jorgensen

Unusual interest is being displayed in ballooning, and as it is fast becoming the favorite sport many persons would like to know how to construct a miniature balloon for making experiments. The following table will give the size, as well as the capacity and lifting power of pilot balloons:

Diameter. Cap. in Cu. Ft. Lifting Power.

5 ft. 65 4 lb.

6 ft. 113 7 lb.

7 ft. 179 11 lb.

8 ft. 268 17 lb.

9 ft. 381 24 lb.

10 ft 523 33 lb.

11 ft. 697 44 lb.

12 ft. 905 57 lb.

The material must be cut in suitable shaped gores or segments. In this article we shall confine ourselves to a 10-ft. balloon. If the balloon is 10 ft. in diameter, then the circumference will be approximately 3-1/7 times the diameter, or 31 ft. 5 in. We now take one-half this length to make the length of the gore, which is 15 ft. 7-1/2 in. Get a piece of paper 15 ft. 7-1/2 in. long and 3 ft. wide from which to cut a pattern, Fig. 1. A line, AB, is drawn lengthwise and exactly in the middle of the paper, and a line, CD, is drawn at right angles to AB and in the middle of the paper lengthways. The intersecting point of AB and CD is used for a center to ascribe a circle whose diameter is the same as the width of the paper, or 3 ft. Divide one-quarter of the circle into 10 equal parts and also divide one-half of the line AB in 10 equal parts. Perpendicular lines are drawn parallel with the line CD intersecting the division points made on the one-half line AB. Horizontal and parallel lines with AB are drawn intersecting the division points made on the one-quarter circle and intersecting the perpendicular line drawn parallel with CD. A line is now drawn from B to E and from E to F, and so on, until all the intersecting lines are touched and the point C is reached. This will form the proper curve to cut the pattern. The paper is now folded on the line AB and then on the line CD, keeping the marked part on the outside. The pattern is now cut, cutting all four quarters at the same time, on the curved line from B to C. When the paper is unfolded you will have a pattern as shown in Fig. 2. This pattern is used to mark the cloth, and after marked is cut the same shape and size.

The cloth segments are sewed together, using a fine needle and No. 70 thread, making a double seam as shown in Fig. 3. When all seams are completed you will have a bag the shape shown in Fig. 4. A small portion of one end or a seam must be left open for inflating. A small tube made from the cloth and sewed into one end will make a better place for inflating and to tie up tightly.

It is now necessary to varnish the bag in order to make it retain the gas. Procure 1 gal. of the very best heavy body, boiled linseed oil and immerse the bag in it. The surplus oil is squeezed out by running the bag through an ordinary clothes wringer several times. The bag is now placed in the sun for a thorough drying. Put the remaining oil in a kettle with 1/8 lb. of beeswax and boil well together. This solution is afterward diluted with turpentine so it will work well. When the bag is dry apply this mixture by rubbing it on the bag with a piece of flannel. Repeat this operation four times, being sure of a thorough drying in the sun each time. For indoor coating and drying use a small amount of plumbic oxide. This will dry rapidly in the shade and will not make the oil hard.

Fill the bag with air by using a pair of bellows and leave it over night. This test will show if the bag is airtight. If it is not tight then the bag needs another rubbing. The next operation is to fill the bag with gas.

Hydrogen gas is made from iron and sulphuric acid. The amounts necessary for a 10-ft. balloon are 125 lb. of iron borings and 125 lb. of sulphuric acid. 1 lb. of iron, 1 lb. of sulphuric acid and 4 lb. of water will make 4 cu. ft. of gas in one hour. Secure two empty barrels of about 52 gal. capacity and connect them, as shown in Fig. 5, with 3/4-in. pipe. In the barrel, A, place the iron borings and fill one-half full of clear water. Fill the other barrel, B, with water 2 in. above the level of the water in barrel A. This is to give a water pressure head against foaming when the generator is in action. About 15 lb. of lime should be well mixed with the water in the barrel B. All joints must be sealed with plaster of Paris. Pour in one-half of the acid into the barrel, A, with the iron borings. The barrels are kept tight while the generation is going on with the exception of the outlet, C, to the bag. When the action is stopped in the generator barrel, A, let the solution run out and fill again as before with water and acid on the iron borings. The outlet, C, should be always connected with the bag while the generator is in action. The 3/4-in. pipe extending down into the cooling tank, B, should not enter into the water over 8 in. When filled with gas the balloon is ready for a flight at the will of the operator.

How to Clean a Clock

It is very simple to clean a clock, which may sound rather absurd. For an amateur it is not always necessary to take the clock to pieces. With a little care and patience and using some benzine, a clean white rag, a sable brush and some oil a clock can be cleaned and put into first-class running order. The benzine should be clean and free from oil. You can test benzine by putting a little on the back of the hand; if it is good it will dry off, leaving the hand quite clean, but if any grease remains on the hand, it is not fit to use.

The oil should be of the very best that can be procured. Vegetable oils should never be used. Clock oil can be procured from your druggist or jeweler. All loose dirt should be removed from the works by blowing with bellows, or a fan, or dusting with a dry brush; in the latter case great care should be exercised not to injure any of the parts. Dip the brush in the benzine and clean the spindles and spindle holes, and the teeth of the escapement wheel. After washing a part, wipe the brush on the rag and rinse in the benzine; this should be repeated frequently, until no more dirt is seen.

When the clock has dried, oil the spindle holes carefully; this may be done with a toothpick or a sliver of woodcut to a fine point. Oil the tooth of the escapement wheel slightly, using a fine brush.

How to Make Blueprint Lantern Slides

Lantern slides of a blue tone that is a pleasing variety from the usual black may be made from spoiled or old plates which have not been developed, by fixing, washing well and then dipping five minutes in the following solution:

Solution A.

Green Iron ammonium citrate 150 gr.

Water 1 oz.

Solution B.

Potassium ferrocyanide 50 gr.

Water 1 oz.

Prepare the solutions separately and mix equal parts for use, at the time of employment. Dry the plates in the dark, and keep in the dark until used. Printing is done in the sun, and a vigorous negative must be used, says the Moving Picture World. Exposure, 20 to 30 minutes. Wash 10 minutes in running water and dry. Brown or purple tones may be had by sensitizing with the following solution instead of the above:

Distilled water 1 oz.

Sliver nitrate 50 gr.

Tartaric or citric acid 1/2 oz.

Bathe the plates 5 minutes, keeping the fingers out of the solution, to avoid blackened skin. Dry in the dark. Print to bronzing under a strong negative; fix in hypo, toning first if desired.

A Substitute for a Ray Filter

Not many amateur photographers possess a ray filter. A good substitute is to use the orange glass from the ruby lamp. This can be held in position in front of the lens with a rubber band. A longer exposure will be necessary, but good cloud effects can be procured in this manner.

Electric Lamp Experiments

Incandescent electric lamps can be made to glow so that they may be seen in a dark room by rubbing the globe on clothing or with a paper, leather or tinfoil and immediately holding near a 1/2-in. Ruhmkorff coil which is in action but not sparking. The miniature 16 cp., 20 and 22-volt lamps will show quite brilliantly, but the 110-volt globes will not glow. When experimenting with these globes everything should be dry. A cold, dry atmosphere will give best results.

How to Make a Simple Wireless Telegraph By Arthur E. Joerin

An efficient wireless-telegraph receiving apparatus for distances up to 1,000 ft. may be constructed in the following manner: Attach a watchcase telephone receiver to a dry cell, or battery, of any make. The negative pole, or zinc, of the cell is connected to a ground wire. This is done by attaching to a gas or water pipe. The positive pole, or carbon, of the cell is connected to the aerial line. This aerial collector can be made in various ways, either by using a screen wire or numerous wires made in an open coil and hung in the air. File a V-shaped groove in the upper end of the carbon of the cell. Attach a small bent copper wire in the binding post that is attached to the zinc of the cell. In the bend of this wire and the V-shaped groove filed into the carbon, lay a needle. This will complete the receiving station. Use a spark coil in connection with a telegraph key for the sending station, making a ground with one wire, and have the other connected with another aerial line.

By connecting the telephone receiver to the cell and at the same time having a short circuit a receiving station is made. As the telephone offers a high resistance, part of the current will try to take the shorter high resistance through the needle. If the waves strike across the needle, the resistance is less, and thus less current travels through the telephone receiver. If the wave ceases, the resistance between the needle and the carbon is increased, and as less current will flow the short way, it is compelled to take the longer metallic way through the windings of the receiver, which will cause the clickings that can be heard.

To Preserve Putty

Putty, when left exposed to the air, will soon become dry and useless. I have kept putty in good condition for more than a year by placing it in a glass jar and keeping it entirely covered with water.

How to Make a Small Storage Battery

The cell of a storage battery consists of two plates, a positive and a negative, made of lead and placed in a dilute solution of sulphuric acid. Large batteries made of large cells have a great number of plates, both positive and negative, of which all positive plates are connected to one terminal and the negative plates to the other terminal. The storage cell, as described below, is the right size to be charged by a few gravity cells and is easily made.

Secure a piece of 1-3/4-in. lead pipe, 5 in. long, and cut both ends smooth and square with the pipe. Solder a circular disk of lead to one end, forming a cup of the pipe. As this cup must hold the sulphuric acid it must be perfectly liquid-tight.

It is also necessary to get another lead pipe of the same length but only 3/4 in. in diameter. In this pipe should be bored as many 1/8 in. holes as possible, except for about 1 in. on each end. One end of this tube is hammered together as shown at A in the sketch to make a pocket to hold the paste. This, of course, does not need to be watertight.

A box of wood is made to hold the larger tube or cup. This box can be square, and the corners left open around the cup can be filled with sawdust. A support is now made from a block of wood to hold the tube, B, in place and to keep it from touching the cup C. This support or block, D, is cut circular with the same diameter as the lead cup C. The lower portion of the block is cut away so it will just fit inside of the cup to form a stopper. The center of this block is now bored to make a hole the same size as the smaller lead pipe. Place the lead pipe in the hole and immerse it in smoking hot paraffine wax, and leave it until the wood has become thoroughly saturated with the hot wax. Use care to keep the wax from running on the lead at any place other than the end within the wood block. Two binding-posts should be attached, one to the positive, or tube B, and the other to the negative, or tube C, by soldering the joint.

A paste for the positive plate is made from 1 part sulphuric acid and 1 part water with a sufficient amount of red lead added to make of thick dry consistency. When mixing the acid and water, be sure to add the acid to the water and not the water to the acid. Also remember that sulphuric acid will destroy anything that it comes in contact with and will make a painful burn if it touches the hands. Stir the mixture with a stick and when a good dry paste is formed, put it into the smaller tube and ram it down until the tube is almost filled. The paste that may have come through the holes is scraped off and the tube set aside to dry. The large tube or cup is filled with a diluted solution of sulphuric acid. This solution should be about one-twelfth acid. The cell is now complete and ready for storing the current. The cell may be charged with three gravity cells. These are connected in series and the positive terminal binding-post on the storage cell is connected to the wire leading from the copper plate in the gravity cell. The other plate is connected to the zinc. The first charge should be run into the cell for about one week and all subsequent charges should only take from 10 to 12 hours.

Fitting a Plug in Different Shaped Holes

A certain king offered to give the prince his liberty if he could whittle a plug that would fit four different shaped holes, namely: a square hole, a round one, an oblong one and a triangular one, says the Pathfinder. A broomstick was used to make the plug and it was whittled in the shape shown in Fig. 1. The holes in the different places as shown in Fig. 2, were fitted by this one plug.

How to Make a Lightning Arrester

Secure a piece of wood about 3-1/2 in. square that will furnish a nice finish and round the corners and make a small rounding edge as shown in the sketch. From a piece of brass 1/16 in. thick cut two pieces alike, A and B, and match them together, leaving about 1/16 in. between their upper edges and fasten them to the wood with binding-posts. The third piece of brass, C, is fitted between the pieces A and B allowing a space of 1/16-in. all around the edge. One binding-post and a small screw will hold the piece of brass, C, in place on the wood. The connections are made from the line wires to the two upper binding-posts and parallel from the lower binding-posts to the instrument. The third binding-post on C is connected to the ground wire. Any heavy charge from lightning will jump the saw teeth part of the brass and is grounded without doing harm to the instruments used.

Contributed by Edwin Walker, Chicago, Ill.

A Home-Made Punt

A flat bottom boat is easy to make and is one of the safest boats, as it is not readily overturned. It has the advantage of being rowed from either end, and has plenty of good seating capacity.

This punt, as shown in Fig. 1, is built 15 ft. long, about 20 in. deep and 4 ft. wide. The ends are cut sloping for about 20 in. back and under. The sides are each made up from boards held together with battens on the inside of the boat near the ends and in the middle. One wide board should be used for the bottom piece. Two pins are driven in the top board of each side to serve as oarlocks.

The bottom is covered with matched boards not over 5 in. wide. These pieces are placed together as closely as possible, using white lead between the joints and nailing them to the edges of the side boards and to a keel strip that runs the length of the punt, as shown in Fig. 2. Before nailing the boards place lamp wicking between them and the edges of the side boards. Only galvanized nails should be used. In order to make the punt perfectly watertight it is best to use the driest lumber obtainable. At one end of the punt a skag and a rudder can be attached as shown in Fig. 3.

Photographers' Printing Frame Stand

When using developing papers it is always bothersome to build up books or small boxes to make a place to set the printing frame in front of the light. Details for making a small stand that is adjustable to any desired height are shown in the sketch. In Fig. 1 is shown the construction of the sliding holder. A piece of 1/4-in. gas pipe, A, is cut 1 in. long and fitted with a thumbscrew, B. The piece of pipe is soldered to the middle on the back side of a piece of metal that is about 4 by 4-1/2 in. with its lower edge turned up to form a small shelf as shown at C. The main part of the stand is made by inserting a 5/16-in. rod tightly into a block of hard maple wood that is 1 in. thick and 3-1/2 in. square (Fig 2). The pipe that is soldered to the metal support will slide up and down the rod and the thumbscrew can be set to hold it at the desired point.

Heat and Expansion

Take an electric light bulb from which the air has not been exhausted and immerse it in water and then break off the point. As there is a vacuum in the bulb it will quickly fill with water. Shake the bulb gently until a part of the water is out and then screw the bulb into a socket with the point always downward. Apply the current and the heated air inside will soon expand and force the water out with great rapidity. Sometimes this experiment can be done several times by using the same bulb.

Contributed by Curtiss Hill, Tacoma, Wash.

Photographing a Streak of Lightning

The accompanying illustration is a remarkable photograph of a streak of lightning. Many interesting pictures of this kind can be made during a storm at night. The camera is set in a place where it will not get wet and left standing with the shutter open and the plate ready for the exposure. Should a lightning streak appear within the range of the lens it will be made on the plate, which can be developed in the usual manner. It will require some attention to that part of the sky within the range of the lens so as to not make a double exposure by letting a second flash enter the open lens.

Contributed by Charles H. Wagner.

Borax may be used as a solvent for shellac gum.

How to Make a Small Single-Phase Induction Motor By C. H. Bell

The following notes on a small single-phase induction motor, without auxiliary phase, which the writer has made, may be of interest to some of our readers, says the Model Engineer. The problem to be solved was the construction of a motor large enough to drive a sewing machine or very light lathe, to be supplied with 110-volt alternating current from a lighting circuit, and to consume, if possible, no more current than a 16-cp. lamp. In designing, it had to be borne in mind that, with the exception of insulated wire, no special materials could be obtained.

The principle of an induction motor is quite different from that of the commutator motor. The winding of the armature, or "rotor," has no connection with the outside circuit, but the current is induced in it by the action of the alternating current supplied to the winding of the field-magnet, or "stator." Neither commutator nor slip rings are required, and all sparking is avoided. Unfortunately, this little machine is not self-starting, but a slight pull on the belt just as the current is turned on is all that is needed, and the motor rapidly gathers speed provided no load is put on until it is in step with the alternations of the supply. It then runs at constant speed whether given much or little current, but stops if overloaded for more than a few seconds.

The stator has four poles and is built up of pieces of sheet iron used for stove pipes, which runs about 35 sheets to the inch. All the pieces are alike and cut on the lines with the dimensions as shown in Fig. 1, with the dotted line, C, to be filed out after they are placed together. Each layer of four is placed with the pointed ends of the pieces alternately to the right and left so as to break joints as shown in Fig. 2. The laminations were carefully built up on a board into which heavy wires had been driven to keep them in place until all were in position and the whole could be clamped down. In the middle of the pieces 1/4-in. holes, B, were then drilled and 1/4-in. bolts put in and tightened up, large holes being cut through the wood to enable this to be done. The armature tunnel was then carefully filed out and all taken apart again so that the rough edges could be scraped off and the laminations given a thin coat of shellac varnish on one side. After assembling a second time, the bolts were coated with shellac and put into place for good. Holes 5-32 in. in diameter were drilled in the corners, A, and filled with rivets, also varnished before they were put in. When put together they should make a piece 2 in. thick.

This peculiar construction was adopted because proper stampings were not available, and as every bit of sheet iron had to be cut with a small pair of tinners' snips, it was important to have a very simple outline for the pieces. They are not particularly accurate as it is, and when some of them got out of their proper order while being varnished, an awkward job occurred in the magnet which was never entirely corrected. No doubt some energy is lost through the large number of joints, all representing breaks in the magnetic circuit, but as the laminations are tightly held together and the circuit is about as compact as it could possibly be, probably the loss is not as great as it would appear at first sight.

The rotor is made of laminations cut from sheet iron, as shown in Fig. 3, which were varnished lightly on one side and clamped on the shaft between two nuts in the usual way. A very slight cut was taken in the lathe afterwards to true the circumference. The shaft was turned from 1/2-in. wrought iron, no steel being obtainable, and is shown with dimensions in Fig. 4. The bearings were cast of babbitt metal, as shown in Fig. 5, in a wooden mold and bored to size with a twist drill in the lathe. They are fitted with ordinary wick lubricators. Figures 6 and 7 are sections showing the general arrangement of the machine.

The stator is wound full with No. 22 double cotton-covered copper wire, about 2-1/2 lb. being used, and the connections are such as to produce alternate poles—that is, the end of the first coil is joined to the end of the second the beginning of the second to the beginning of the third, and the end of the third to the end of the fourth, while the beginnings of the first and fourth coils connect to the supply.

The rotor is wound with No. 24 double cotton-covered copper wire, each limb being filled with about 200 turns, and all wound in the same direction. The four commencing ends are connected together on one side of the rotor and the four finishing ends are soldered together on the other. All winding spaces are carefully covered with two layers of cambric soaked in shellac, and as each layer of wire was wound, it was well saturated with varnish before the next was put on.

This type of motor has drawbacks, as before stated, but if regular stampings are used for the laminations, it would be very simple to build, having no commutator or brushes, and would not easily get out of order. No starting resistance is needed, and as the motor runs at constant speed, depending upon the number of alterations of the supply, a regulating resistance is not needed.

Carbolic Acid Burns

The pain of carbolic acid burns can be relieved promptly by washing with alcohol, if applied immediately. If too late for alcohol to be of use, brush with water containing saturated solution of picric acid.

How to Make a Paper Book Cover

Book covers become soiled in handling and especially school books. Various methods are applied for making a temporary cover that will protect the book cover. A paper cover can be quickly made by using a piece of paper larger than both covers on the book when they are open. Fold the paper on the long dotted line, as shown in Fig. 1. When the folds are made the paper should then be just as wide as the book cover is high. The ends are then folded on the short dotted lines, which will make it appear as shown in Fig. 2. The paper thus folded is placed on the book cover as shown in Fig. 3.

Contributed by C. E. McKinney, Jr., Newark, N. J.

How to Make Lantern Slides

The Camera as It is Arranged in Front of the Window for Reducing the Size of a Picture, and the Method of Binding the Slides

The popularity of lantern slides, and especially of colored ones, as a means of illustrating songs, has caused so large a demand for this class of work that almost any amateur may take up slide making at a good profit. The lantern slide is a glass plate, coated with slow and extremely fine-grained emulsion. The size is 3-1/4 by 4 in. A lantern slide is merely a print on a glass plate instead of on paper. Lantern slides can be made in two different ways. One is by contact, exactly the same as a print is made on paper, and the other by reduction in the camera. In making slides by contact, select the negative and place it in the printing frame and put the lantern plate upon it, film to film. Clamp down the back and expose just as in making a print. A good method of exposing is to hold a lighted match about 3 in. from the frame for three or more seconds according to the density.

Development is carried on in the same manner as with a negative. The image should appear in. about a minute, and development should be over in three or four minutes. If the exposure has been correct, the high lights will stay white throughout the development and will come out as clear glass after fixing. It is best to use the developers recommended by the manufacturer of the plates used, the formulas being found in each package of plates. It is best, also, to use a plain fixing bath, which must be fresh and kept as cool as possible in hot weather.

The lantern-slide film that is new on the market can be handled in the same manner as the glass-plate slide, except that the binding is different. The results are the same and the slides are not so bulky to handle. Being unbreakable, they are much used by travelers. The manner of binding them for use in a lantern is described on the circular enclosed with the film.

When the negative is larger than the lantern-slide plate, and it is desirable to reduce the entire view upon the slide, a little extra work will be necessary. Select a room with one window, if possible, and fit a light-proof frame into it to keep out all light with the exception of a hole in which to place the negative, as shown in Fig. 1. Unless this hole is on a line with the sky it will be necessary to place a sheet of white cardboard at an angle of 45 deg. on the outside of the frame to reflect the light through the negative as shown in Fig. 2. Make or secure an inside kit to place in the plate holder of your camera to hold the lantern slide plate as shown in Fig. 3. Draw lines with a pencil, outlining on the ground glass of the camera the size of the lantern slide plate, and in the place where the plate will be in the plate holder when placed in position in the camera. This will enable you to focus to the proper size. Place the camera in front of the hole in the frame, place the negative in the hole and focus the camera for the lantern slide size. Expose with a medium stop for about 20 seconds and treat the plate the same as with the contact exposure.

When dry the lantern slide plate may be tinted any color by means of liquid colors. These can be purchased from any photo material store. In coloring the slide plate it is only necessary to moisten the gelatine film from time to time with a piece of cloth dampened in water. The colors may then be spread evenly with a soft brush, which should be kept in motion to prevent spots. The slide is put together by placing a mat made of black paper, as shown in Fig. 4, on the gelatine side of the lantern slide, A, Fig. 5, and then a plain glass, B, over the mat, C, and the three bound together with passe-partout tape, D. Contrasty negatives make the best slides, but the lantern slide plate should be made without any attempt to gain density.

How To Make A Porch Swing Chair

The material needed for making this porch swing chair are two pieces of round wood 2-1/2 in. in diameter and 20 in. long, and two pieces 1-1/4 in. in diameter and 40 in. long. These longer pieces can be made square, but for appearance it is best to have them round or square with the corners rounded. A piece of canvas, or other stout cloth, 16 in. wide and 50 in. long, is to be used for the seat. The two short pieces of wood are used for the ends of the chair and two 1-in. holes are bored in each end of them 1-1/2 in. from the ends, and between the holes and the ends grooves are cut around them to make a place to fasten ropes, as shown at B, Fig. 1. The two longer pieces are used for the sides and a tenon is cut on each end of them to fit in the 1-in. holes bored in the end pieces, as shown at A, Fig. 1. The canvas is now tacked on the end pieces and the pieces given one turn before placing the mortising together.

The chair is now hung up to the porch ceiling with ropes attached to a large screw eye or hook. The end of the chair to be used for the lower part is held about 16 in. from the floor with ropes direct from the grooves in the end pieces to the hook. The upper end is supported by using a rope in the form of a loop or bail, as shown in Fig. 2. The middle of the loop or bail should be about 15 in. from the end piece of the chair. Another rope is attached to the loop and through the hook and to a slide as shown. This will allow for adjustment to make the device into a chair or a hammock.

Contributed by Earl R. Hastings, Corinth, Vt.

How to Find the Blind Spot in the Eye

Make a small black circular dot 1/2 in. in diameter on a piece of cardboard and about 3 in. from the center of this dot draw a star. Hold the cardboard so that the star will be directly in front of one eye, while the dot will be in front of the other. If the star is in front of the left eye, close the right eye and look steadily at the star while you move the cardboard until the point is reached where the dot disappears. This will prove the presence of a blind spot in a person's eye. The other eye can be given the same experiment by turning the cardboard end for end. The blind spot does not indicate diseased eyes, but it simply marks the point where the optic nerve enters the eyeball, which point is not provided with the necessary visual end organs of the sight, known as rods and cones.

Beeswax Substitute

A wax from the rafie palm of Madagascar is being used as a substitute for beeswax.

Home-Made Water Wheel Does Family Washing

The accompanying sketch illustrates a very ingenious device which does the family washing, as well as to operate other household machines. A disk 1 in. in thickness and 10 in. in diameter was cut from a piece of rough board, and on its circumference were nailed a number of cup-shaped pieces cut from old tin cans. A hole was then bored through the center of the disk and an old piece of iron rod was driven through to form a shaft. Two holes were then bored opposite each other through the sides of a wooden box in which the disk was placed, allowing the shaft to project through the holes. A small grooved wooden pulley was driven tightly on one of the projecting ends of the shaft. The top of the box was then tightly closed and a hole, large enough to admit the nozzle of a garden hose, was bored so that the jet of water would flow upon the tin buckets that were nailed to the circumference of the wheel or disk. Another hole was bored in the bottom of the box large enough to allow the waste water to run away freely. A belt, made from an ordinary sash cord, was run from the small pulley on the waterwheel to a large pulley, as shown in Fig. 1. A pitman was attached to the large pulley, which operates the washing machine by its reciprocating motion, and the length of the stroke is adjusted by moving the position of the hinge joint on the arm of the washing machine, as shown in Fig. 2. The pressure at the nozzle is about 20 lb. per square inch, and is sufficient to drive the waterwheel under all ordinary circumstances.

Contributed by P. J. O'Gara, Auburn, Cal,

An Optical Illusion

When looking at the accompanying sketch you will say that the letters are alternately inclined to the right and left. They are not so and can be proved by measuring the distance of the top and bottom of any vertical strokes from the edge of the entire block. They will be found to be exactly the same distance. Or take any of the horizontal strokes of the four letters and see how far their extremities are from the top and bottom of the entire block. It will be found that a line joining the extremities of the strokes are strictly parallel to the top or bottom and that they are not on a slant at all. It is the slant of the numerous short lines that go to make up the letter as a whole that deceives the eye.

Home-Made Micrometer

It often becomes necessary to find the thickness of material so thin, or inconvenient to measure, that a rule or other measuring device will not serve the purpose. A simple, fairly accurate, and easily made apparatus of the micrometer form may be constructed as shown by the accompanying sketch. Secure a common iron or brass bolt about 1/4-in. in diameter and about 2-1/2 in. long, with as fine a thread as possible, and the thread cut to within a short distance of the head of the bolt. The head of the bolts should have a slot cut for the use of a screwdriver. Clamp together two blocks of wood with square corners which are about 1 in. wide, 3/4 in. thick and 2-1/2 in. long and fasten them together with small pieces nailed across the ends. The width of the blocks will then be about 2 in. Bore a 1/4-in. hole through the center of the blocks in the 2 in. direction. Remove the clamp and set the nut into one of the blocks, so that the hole will be continuous with the hole in the wood. Cut out a piece from the block combination, leaving it shaped like a bench, and glue the bottoms of the legs to a piece of thin board about 2-1/2 in. square for a support.

Solder one end of a stiff wire that is about 2 in. long to the head of the bolt at right angles to the shaft, and fix a disc of heavy pasteboard with a radius equal to the length of the wire, and with its circumference graduated into equal spaces, to serve in measuring revolutions of the end of the wire, to the top of the bench. Put the bolt in the hole, screwing it through the nut, and the construction is complete. The base is improved for the measuring work by fastening a small piece of wood on the board between the legs of the bench. A small piece of metal is glued on this piece of wood at the point where the bolt meets it.

Find the number of threads of the screw to the inch by placing the bolt on a measuring rule, and counting the threads in an inch of its length. The bolt in making one revolution will descend a distance equal to the distance between the threads.

The device is used by placing the object whose thickness is to be measured on the base under the bolt, and screwing the bolt down until its end just touches the object, then removing the object, and screwing the bolt down until its end just touches the base, carefully noting while doing so the distance that the end of the wire moves over the scale. The part of a rotation of the bolt, or the number of rotations with any additional parts of a rotation added, divided by the number of threads to the inch, will be the thickness of the object. Quite accurate measurements may be made with this instrument, says the Scientific American, and in the absence of the expensive micrometer, it serves a very useful purpose.

Another Electric Lamp Experiment

Break a portion of the end off from a 16-cp. globe that has been thrown away as useless. Shake the globe until all the filament is broken away, leaving only the ends of the platinum wire exposed. Screw the globe into a socket that sets upright and fill it with salt water. Make one connection to the socket from the positive wire of a 110 volt circuit and the other to a ground. When the current is turned on small stars will be seen in the globe, which show up fine at night.

Contributed by Lindsay McMillan, Santa Maria, Oal.

Removing Ink Stains

Two or three applications of milk which are wiped up with a dry cloth will remove india ink spots on carpets.

Feat of Balancing on Chairs

Among the numerous physical exercises is the feat of balancing on the two rear legs of a chair while one foot rests on the front part of the seat and the other on the back of the chair. This may appear to be a hard thing to do, yet with a little practice it may be accomplished. This exercise is one of many practiced by the boys of a boys' home for an annual display given by them. A dozen of the boys will mount chairs at the same time and keep them in balance at the word of a commanding officer.

How to Make a Merry-Go-Round Swing

A 6 by 6-in. piece of wood 12 ft. long is used for the center pole. Bore a 3/4-in. hole in each end to a depth of 6 in. Place a 3/4-in. bolt in each hole, the bolt being long enough to protrude 2 in. beyond the end of the wood. Short pieces of wood are nailed on the center pole about 2 ft. from the end that is to be used for the bottom. This should form a hub on which to place the inner ends of the extending spokes that hold the platform. The spokes are made from twelve pieces of 2 by 4-in. material 12 ft. long.

Usually a wheel can be found in a scrap pile suitable to place on the pin that is in the top end of the center pole. The wheel should be open or have spokes. This wheel is used to attach wires for guying. The bottom pin in the center pole is placed in a hole that is bored into a block of wood about 12-in. square and 3 or 4 in. thick. A piece of sheet metal should be drilled and placed on the pin between the block and end of the pole to make a smooth bearing. The center pole is now placed in position and guyed with six wires that are about 35 ft. long. Stakes are driven into the ground and the wires fastened to them and to the wheel at the top end of the pole. Care should be taken when attaching the wires to get the center pole to stand perpendicular. Twelve hooks should be placed at equal distances around the center pole about 1 ft. from the top end. Wires are fastened to these hooks and to the twelve 2 by 4-in. pieces used for the spokes. The wires should be tied around each spoke about 2 ft. from the ends. Space the spokes with equal divisions and cover the outer 2 ft. of the ends with boards, as shown in the plan sketch on the right hand end of the drawing. The boards may be nailed or bolted. If bolted and the wires made in a loop at the hooks, the swing can easily be taken apart and changed from one place to another.

Contributed by A. O. Graham, Fort Worth, Tex.

Home-Made Arc Lamp

The frame of the lamp is made from bar metal 3/4 in. wide and 1/8 in. thick, bent and welded to make a continuous loop in the shape as shown at G in the sketch. This frame should be about 10-1/2 in. long with the upper or wider part 4 in. long, and the lower part 6-1/2 in. long. The width should be about 5-1/4 in. at the top and 4 in. at the bottom. A cross bar, L, made of the same material, is fitted into the off-set in the frame and riveted. Holes are drilled through the frame and brass bushings, H and J, are fitted for bearings to receive the adjusting brass rod, B, which should be 1/4 in. in diameter. A brass curtain rod can be used for the rod B, and on its lower end a socket, P, is soldered.

A piece of brass 2 in. long, 1/2 in. wide and 1/8 in. thick is used for the armature, A, to be operated by the magnet coil, C. The coil, C, is made in the usual manner by wrapping No. 14 cotton-covered magnet wire on a wooden spool that has a soft iron core. The spool is about 2-1/2 in. long. The armature, A, is drilled, making a hole just a little larger than the rod, B, and is adjusted in place by two set screws, D and E. A soft piece of iron, F, is fastened to the opposite end of the armature with a screw, which should be placed directly under the end of the coil's core. This end of the armature may be kept from swinging around by placing it between a U-shaped piece of brass fastened to the cross piece L. At the bottom end of the frame, and directly centering the holes H and J, a hole is drilled to receive a hard rubber bushing, R, for insulating the brass ferrule, S, that holds the lower carbon.

One connection is made from the main to the upper binding-post, which is in turn connected to one terminal of the coil, C, the other coil terminal being attached to the frame. The other main connection is made to the lower binding-post, which is also connected to the brass ferrule, S, by soldering. The two binding-posts are insulated from the frame the same as the ferrule S. When using on a 110-volt circuit there must be some resistance in connection, which may be had by using German silver wire, or a water rheostat heretofore described.

Contributed by Arthur D. Bradley. Randolph, Mass.

Irrigation

The Mexican government has appropriated $25,000,000 for irrigation work.

How to Hang Your Hat on a Lead Pencil

Take a smooth hexagon lead pencil, one without either rubber or metal end, and place it against a door or window casing; then with a firm, heavy pressure slide the pencil some 3 or 4 in. and it will stay as if glued to the casing. You may now hang your hat on the end of the pencil.

When you slide the pencil along the casing, do it without any apparent effort, and it will appear to your audience as though you had hypnotized it. This is a very neat trick if performed right. Figure 1 shows the pencil on the casing and Fig. 2 the hat hanging on it.

Tying a Knot for Footballs

One of the most prominent English football clubs kept the tying of this knot on the rubber hose of their football a secret and never allowed all of its members to know how it was tied. This tie can be used on grain sacks, and in numerous other like instances. Make one loop in the cord and then another exactly the same way, as shown in Fig. 1, placing the end of the cord under the first loop, then pulling at each end of the cord as in Fig. 2.

A.E.J.

Stove Polish

Stove polish consists of 2 parts graphite, 4 parts copperas and 2 parts bone black, mixed with water to form a paste.

How to Give an Electric Shock While Shaking Hands

There is nothing quite so startling as to receive an electric shock unexpectedly and such a shock may be given to a friend while shaking hands upon meeting. The shock produced is not harmful and the apparatus can be carried in the pocket. It consists of a small induction coil that can be constructed at home.

The core of the coil, A, Fig. 1, is constructed in the usual manner, of small soft-iron wire to make a bundle about 3/16 in. in diameter and 2 in. long. The coil ends are made from cardboard, about 1 in. in diameter, with a 3/16-in. hole in the center. The hole should be cut as shown in Fig. 2, so as to have four small pieces that can be bent out, leaving the projections as shown. After wrapping three or four turns of paper around the bundle of wires the cardboard ends are put on with the projections inside, so the coils of wire will hold them in place. About 70 turns of No. 24 gauge double covered magnet wire is first placed on the core, for the primary, and then 1,500 turns of No. 32 or 34 gauge double-covered wire is wrapped on top of the primary, for the secondary. Sufficient length of wire must be left outside at each end of both windings to make connections. The vibrator B, Fig. 1, and the support C are made from thin spring steel, about 1/8 in. wide, bent as shown and securely fastened to the cardboard end of the coil. The armature is made from a soft piece of iron, about 3/16 in. in diameter and 1/16 in. thick, which is soldered to the end of the vibrator directly opposite the end of the core. A small screw is fitted in the end of the support, C, for adjustment, which should be tipped with platinum and also a small piece of platinum placed where the screw will touch the vibrator, B.

One of the primary wires is connected to the screw support. The vibrator, is connected to a flash lamp battery, D. The other primary wire is connected to a switch, S, which in turn is connected to the other terminal of the battery. The switch, S, may be made from a 3/8-in. cork with the wires put through about 3/16 in. apart and allow them to project about 1/2 in. The plate E is cut about 1/2 in. square from a piece of copper and is fastened to the heel of one shoe and connected with a wire from the secondary coil which must be concealed inside of the trouser leg. The other secondary wire is connected through the coat sleeve to a finger ring, F. The vibrator screw must be properly adjusted. When the vibrator is not working the armature should be about 1/16 in. from the core and directly opposite.

The coil when complete will be about 2-1/2 in. long and 1 in. in diameter. The coil can be placed in an old box that has been used for talcum powder or shaving stick. The space around the coil in the box can be filled with paper to keep it tight.

The coil and battery are carried in the pockets and the cork button put in the outside coat pocket, where it can be pressed without attracting attention.

Experiment with Heat

Place a small piece of paper, lighted, in an ordinary water glass. While the paper is burning turn the glass over and set into a saucer previously filled with water. The water will rapidly rise in the glass, as shown in the sketch.

How to Attach a Combination Trunk Lock

A small combination lock for chests can be purchased for a small sum of money and attached to a trunk cover after first removing the old lock as shown in Fig. 1. It is necessary to add 1/2-in. to the thickness of the trunk lid or cover. This may be done by placing a brass plate 1/8-in. thick on the outside and a board 3/8-in. thick on the inside. The lock, brass plate, board and trunk cover are all securely riveted together. The support for the dial is soldered to the brass plate.

The hasp, if that be the name for the double toothed arrangement that catches into the lock, was to be secured by only three brass screws, which seemed to be insufficient, says a correspondent of the Metal Worker; therefore a piece of heavy tin was formed over the front of the trunk, which is only 3/8-in. board, the hasp tinned and soldered to the back of the now U-shaped tin, and the tin placed over the board and all fastened in position. The tin is 4 in. wide, 16 in. long and when placed over the board, it laps down about 8 in. between the boards, and the same distance inside of the new board, as shown by the heavy line in the cross section, Fig. 1. Wrought nails are used which pass twice through the tin and both boards, and then well clinched. The three screws were then put in the hasp.

The knob on the dial extends out too far, which may be filed off and two holes substituted, as shown, with which to operate the dial. An old key is filed down in the shape shown in Fig. 2 to fit the two holes. As the dial is convex it will need protection to prevent injury by rough handling. A leather shield may be used for this purpose, which is cut with two holes, one for the key and the other to permit the operator to observe the numbers on the dial. The shield answers a further purpose of preventing any bystander from noting the numbers on the dial.

An Electric Illusion Box

The accompanying engravings show a most interesting form of electrically operated illusion consisting of a box divided diagonally and each division alternately lighted with an electric lamp. By means of an automatic thermostat arranged in the lamp circuit causing the lamps to light successively, an aquarium apparently without fish one moment is in the next instant swarming with live gold fish; an empty vase viewed through the opening in the box suddenly is filled with flowers, or an empty cigar box is seen and immediately is filled with cigars.

These electric magic boxes as shown are made of metal and oxidized copper finished, but for ordinary use they can be made of wood in the same shape and size. The upper magic boxes as are shown in the engraving are about 12 in. square and 8-1/2 in. high for parlor use and the lower boxes are 18 in. square and 10-1/2 in. high for use in window displays. There is a partition arranged diagonally in the box as shown in the plan view, which completely divides the box into two parts. One-half the partition is fitted with a plain, clear glass as shown. The partition and interior of the box are rendered non-reflecting by painting with a dull, not shiny, black color. When making of wood, a door must be provided on the side or rear to make changes of exhibits. If the box is made large enough, or in the larger size mentioned, openings may be made in the bottom for this purpose, and also used in case of performing the magic trick of allowing two persons to place their heads in the box and change from one to the other. The electric globes are inserted as shown at LL through the top of the box, one in each division. When the rear part is illuminated, any article arranged within that part will be visible to the spectator looking into the box through the front opening, but when the front part is illuminated, and the back left dark, any article placed therein will be reflected in the glass, which takes the same position to the observer as the one in the rear. Thus a plain aquarium is set in the rear part and one with swimming fish placed in the front, and with the proper illumination one is changed, as it appears, into the other. When using as a window display, place the goods in one part and the price in the other. Many other changes can be made at the will of the operator.

Electric lamps may be controlled by various means to produce different effects. Lamps may be connected in parallel and each turned on or off by means of a hand-operated switch or the button on the lamp socket, or if desired a hand-operated adjustable resistance may be included in the circuit of each lamp for gradually causing the object to fade away or reappear slowly.

Instead of changing the current operated by hand, this may be done automatically by connecting the lamps in parallel on the lighting circuit and each connected in series with a thermostatic switch plug provided with a heating coil which operates to automatically open and close the circuit through the respective lamp.

When there is no electric current available, matches or candles may be used and inserted through the holes H, as shown in the sketch, alternately.

Replace Dry Putty

Painting over putty that has not become dry will cause scaling or cracking around the edges of the putty.

Photo Print Washing Tank

The accompanying sketch shows a simple form of a print washing tank that tips from side to side by the weight of the water. For prints 4 by 5 and 5 by 7-in. a tank 2 ft. long and 1 ft. wide will be about the right size. This tank is then divided with a partition placed exactly in the center. This partition should extend 3 or 4 in. above the top of the tank. The partition may also extend below the tank about 1-1/2 in., or a piece of this width put on the bottom, as shown at A in the sketch. A row of holes about 1/2 in. in diameter is bored through each end of the tank, as shown at B. These holes will allow the water to spill out while the opposite side is filling. The tank may be made from 1/2-in. material and when completed as shown, lined with oil cloth to make it watertight. The tank is placed with the partition directly under a water tap and the flow of water will cause it to tip from time to time, keeping the prints constantly moving about in the water.

Home-Made Soldering Clamps

Take a cotter pin and bend it over a small rod to bring the points together, as shown in the sketch. This will make a spring clamp that is opened to slip over the articles to be clamped together by inserting a scratch awl or scriber between the legs at the bowed portion. To make a more positive clamp before bending the legs to a bow, slip a short coil of wire over the pin, passing it down to the ring end. Wire 1/32 in. in diameter wound over a wire slightly larger in diameter than that of the cotter will do. In soldering, smoke the legs well to avoid solder adhering to them. The clamp is tightened by pushing up the coil ring toward the bow of the legs and then twisting it like a nut, the coil being wound right-handed, so that it will have a screw effect.

A Telephone Experiment

If the small apparatus, as shown in the accompanying sketch, is attached to the under side of an ordinary dining table, it will, if connected to a telephone circuit, set the table in vibration, so that any number of people who put their ears flat upon the table will hear the voice of a person speaking from a distance, apparently coming out of the table, says the Model Engineer.

A small piece of wood, A, Fig. 1, is cut about 5 in. square, to the center of which is attached a small piece of soft iron wire, such as used for cores of induction coils, about 4 in. long and bent in the form of a hook at the lower end, as shown at B. This wire is attached to the block of wood, A, as shown in Fig. 2. The end of the wire is soldered to a small brass plate which is set in the block so it will be level or flush with the top of the block and then fastened with two screws. The block A is fastened to the under side of the table with two screws. A small coil, C, is made by winding No. 24 silk or cotton covered wire around a small tube, either a piece of glass, a short straw or a quill. The coil is made tapering as shown without using wood ends. This coil is slipped over the wire B previous to soldering it to the small brass plate. The ends of the coil are connected to two binding-posts which are fastened to the block A. A small lead weight weighing 2 or 3 oz. is hung on the hook made in the lower end of the wire B.

When all connections are made, as shown in Fig. 1, and the block fastened to the under side of the table, the apparatus is ready for use, and has only to be connected to an ordinary telephone transmitter and batteries as shown. The apparatus will work to a certain extent even if the weight is removed, though not so clear.

Wax Wood Screws

Some workmen use tallow on lag or wood screws. Try beeswax for this purpose. It is much cleaner to use and is just as good if not better.

How to Make an Induction Coil

A small shocking coil, suitable for medical purposes, may be constructed of materials found in nearly every amateur mechanic's collection of odds and ends. The core, A, Fig. 1, is a piece of round soft iron rod about 1/4 in. in diameter and about 4 in. long. A strip of stiff paper about 3/4 in. wide is covered with glue and wrapped around one end of the core, as shown at B, until the diameter is about 3/8 in. The portion of the core remaining uncovered is then wrapped with a piece of paper about 4 in. wide. No glue is used on this piece, as it is removed later to form the space, C, after the paper shell, D, has been wound upon it. This paper shell is made of stiff paper and glue the same as B and is made about 3/64 in. thick. Two pieces of hardwood, EE, 1-3/4 in. square and about 5/16 in. thick, are drilled in the center and glued on the ends of the paper shell as shown.

The primary winding consists of 4 or 5 layers of No. 18 or 20 single cotton-covered magnet wire, the ends of which may be passed through small holes in the wooden ends. If a drill small enough is not available, the holes may be made with a hot knitting needle or a piece of wire heated to redness. After the primary coil is wound it should be thoroughly insulated before winding the secondary. This may be done by wrapping with 4 or 5 thicknesses of paper.

The secondary coil should be wound with single covered wire, preferably silk-covered, although cotton will do. The more turns there are on the secondary the higher the voltage will be, so the wire used must be fine. Number 32 to 36 will give good results, the latter giving more voltage but less amperage. Each layer of the secondary winding should be insulated from the others by a piece of thin paraffined paper wrapped over each layer as it is finished. It is well not to wind to the extreme ends of the paper insulations, but to leave a space of about 1/8-in. at each end of the winding to prevent the wires of one layer slipping over the ends of the paraffin paper and coming in contact with the layer beneath, thus causing a short circuit. The secondary winding should have at least a dozen layers and should be carefully wound to prevent short circuiting.

In order to reduce the strength of the current a piece of brass tubing, F, is pushed into the space, C, surrounding the core, or if no brass tubing of the required size is on hand, roll a paper tube, cover with 4 or 5 thicknesses of tinfoil and then wrap with more paper, using glue to hold the tinfoil in place and to keep the tube from unwinding. When the tube is pushed all the way in, the current produced will be almost unnoticeable, but when it is withdrawn the current will be so strong that a person cannot let go the handles until the coil is shut off. After the secondary coil is wound it should be covered with stiff paper, and the whole coil, including the wood ends, should then be enameled black.

It is then ready to be mounted on a wooden base as shown in Fig. 2. The secondary terminals are connected to the binding-posts, AA, which may be fastened on the base if desired. One wire from the primary is connected with the binding-post, B, and the other is connected with the armature, D, which may be taken from an old electric bell. The contact screw, E, also from an electric bell, is connected to the binding-post, C. The contact spring, F, should be bent against and soldered to the armature in order to make the vibrations more rapid.

If a false bottom is used on the base, all the wiring may be concealed, which adds greatly to the appearance and if desired a small switch may be added. The handles, which may be old bicycle pumps or electric light carbons, are connected to the binding-posts, AA, by means of wires about 3 or 4 ft. long. This coil when operating with the tube pulled all the way out and connected to a single dry cell will give a current stronger than most persons can stand.

Home-Made Toaster

Each outside frame of the toaster is made from one piece of wire 30 in. long. These are bent in a perfect square making each side 7-in. long. This will allow 1 in. on each end for tying by twisting the ends together. The first two wires inside and on each side of each frame are 8 in. long. Eight wires will be required for this purpose and as they are 8 in. long 1/2 in. is allowed on each end for a bend around the outside frame, as shown in the sketch. The two middle wires are extensions of the handles. Each of these wires are made from a piece about 26 in. long and bent in the shape of a U. The ends of the wire are bent around the frame in the same manner as the other wires. This will leave the handle laying across the other side of the frame. The frame is fastened to the handle on this side by giving the handle one turn around the frame. The inside edges of the frame are now tied together with a small ring of wire which is loose enough to allow each half to swing freely.

C. D. M.

Home-Made Shocking Machine

An ordinary electric bell may be connected up in such a way as to produce the same results as an expensive shocking machine. The connections are made from the batteries to the bell in the usual manner. Two other wires are then connected, one to the binding-post of the bell that is not insulated from the frame and the other to the adjusting screw on the make and break contact of the bell as shown in the sketch. The other ends of the wires are connected each to a common table knife. This will give quite a good shock and a much larger one can be had by placing one knife in a basin of water and while holding the other knife in one hand, dipping the fingers of the other hand in the water.

Contributed by D. Foster Hall.

Mahogany Wood Putty

Mix venetian red with quite thick arabic muscilage, making it into a putty, and press this well into the cracks of mahogany before finishing. The putty should be colored to suit the finish of the wood, says the Master Painter, by adding such dry color to the gum as will give the best result.

How to Make a Thermoelectric Battery By Arthur E. Joerin

A novel way of producing an electric current by means of hot and cold water, heat from a match or alcohol lamp, is obtained from a device constructed as shown in the sketch. Take two hardwood boards, marble, or slate plates, about 8 or 10 in. long, place them together, as in Fig. 1, and mark and drill about 500 holes. These two pieces should be separated about 8 in. and fastened with boards across the ends, as shown in Fig. 2.

Take soft copper wire, not smaller than No. 18 gauge, and cut in lengths to pass through the holes in the two boards, leaving sufficient end to make a tie. It will require about 70 ft. of wire to fill one-half the number of holes. Also, cut the same number of lengths from the same gauge galvanized-iron wire to fill the remaining holes. The wires are put through the holes in the boards alternately, that is: begin with copper, the next hole with iron, the next copper, the next iron, and so on, twisting the ends together as shown in Fig. 3. The connections, when complete, should be copper for the first and iron for the last wire.

When the whole apparatus is thus strung, the connections, which must be twisted, can be soldered. Connect one copper wire to the bell and the other terminal, which must be an iron wire, to the other post of the bell. The apparatus is then short-circuited, yet there is no current in the instrument until a lighted match, or, better still, the flame of an alcohol lamp is placed at one end only.

Best results are obtained by putting ice or cold water on one side and a flame on the other. The experimenter may also place the whole apparatus under sink faucets with the hot water turned on at one terminal and the cold water at the other. The greater the difference of temperature in the two terminals, the more current will be obtained.

Very interesting experiments may thus be performed, and these may lead to the solving of the great thermoelectric problem.

How to Make a Hygrometer

Mount a wire on a board which is used for a base and should be 3/8 by 4 by 8 in., as shown in the sketch. A piece of catgut—a string used on a violin will do—is suspended from the bent end of the wire. A hand or pointer is cut from a piece of tin and secured to the catgut string about 1/2 in. from the base. A small piece of wood and some glue will fasten the pointer to the string. The scale is marked on a piece of cardboard, which is fastened to the base and protected with a piece of glass.

Contributed by J. Thos. Rhamstine.

Softening Leather in Gloves and Boots

The leather in high-top boots and gauntlet gloves may be softened and made waterproof by the use of plain mutton tallow. Apply hot and rub in well with the fingers.

How to Make a Mission Library Table

This Picture Is from a Photograph of the Mission Table Described

The mission library table, the drawings for which are here given, has been found well proportioned and of pleasing appearance. It can be made of any of the several furniture woods in common use, such as selected, quarter-sawed white oak which will be found exceptionally pleasing in the effect produced.

If a planing mill is at hand the stock can be ordered in such a way as to avoid the hard work of planing and sandpapering. Of course if mill-planed stock cannot be had, the following dimensions must be enlarged slightly to allow for "squaring up the rough."

For the top, order 1 piece 1-1/8 in. thick, 34 in. wide and 46 in. long. Have it S-4-S (surface on four sides) and "squared" to length. Also, specify that it be sandpapered on the top surface, the edges and ends.

For the shelf, order 1 piece 7/8 in. thick, 22 in. wide and 42 in. long, with the four sides surfaced, squared and sandpapered the same as for the top. For the side rails, order 2 pieces 7/8 in. thick, 6 in. wide and 37 in. long, S-4-S and sanded on one side. For the end rails, 2 pieces 7/8 in. thick, 6 in. wide and 25 in. long. Other specifications as for the side rails.

For the stretchers, into which the shelf tenons enter, 2 pieces 1-1/8 in. thick, 3-3/4 in. wide and 25 in. long, surfaced and sanded on four sides. For the slats, 10 pieces 5/88 in. thick, 1-1/2 in. wide and 17 in. long, surfaced and sanded on four sides. For the keys, 4 pieces 3/4 in. thick, 1-1/4 in. wide and 2-7/8 in. long, S-4-S. This width is a little wide; it will allow the key to be shaped as desired.

The drawings obviate any necessity for going into detail in the description. Fig. 1 gives an assembly drawing showing the relation of the parts. Fig. 2 gives the detail of an end. The tenons for the side rails are laid off and the mortises placed in the post as are those on the end. Care must, be taken, however, not to cut any mortises on the post, below, as was done in cutting the stretcher mortises on the ends of the table. A good plan is to set the posts upright in the positions they are to occupy relative to one another and mark with pencil the approximate positions of the mortises. The legs can then be laid flat and the mortises accurately marked out with a fair degree of assurance that they will not be cut where they are not wanted and that the legs shall "pair" properly when effort is made to assemble the parts of the table.

The table ends should be glued up first and the glue allowed to harden, after which the tenons of the shelf may be inserted and the side rails placed.

There is a reason for the shape, size and location of each tenon or mortise. For illustration, the shape of the tenon on the top rails permits the surface of the rail to extend almost flush with the surface of the post at the same time permitting the mortise in the post to be kept away from that surface. Again, the shape of the ends of the slats is such that, though they may vary slightly in length, the fitting of the joints will not be affected. Care must be taken in cutting the mortises to keep their sides clean and sharp and to size.

In making the mortises for the keyed tenons, the length of mortise must be slightly in excess of the width of the tenon—about 1/8-in. of play to each side of each tenon. With a shelf of the width specified for this table, if such allowance is not made so that the tenons may move sideways, the shrinkage would split the shelf.

In cutting across the ends of the shelf, between the tenons, leave a hole in the waste so that the turning saw or compass saw can be inserted. Saw within one-sixteenth of the line, after which this margin may be removed with chisel and mallet.

In Fig. 3 is shown two views of the keyed tenon and the key. The mortise for the key is to be placed in the middle of the tenon. It will be noted that this mortise is laid out 1-1/16 in. from the shoulder of the tenon while the stretcher is 1-1/8 in. thick. This is to insure the key's pulling the shelf tightly against the side of the stretcher.

Keys may be made in a variety of shapes. The one shown is simple and structurally good. Whatever shape is used, the important thing to keep in mind is that the size of the key and the slant of its forward surface where it passes through the tenon must be kept the same as the mortise made for it in the tenon.

The top is to be fastened to the rails by means either of wooden buttons, Fig. 4, or small angle irons.

There are a bewildering number of mission finishes upon the market. A very satisfactory one is obtained by applying a coat of brown Flemish water stain, diluted by the addition of water in the proportion of 2 parts water to 1 part stain. When this has dried, sand with number 00 paper, being careful not to "cut through." Next, apply a coat of dark brown filler; the directions for doing this will be found upon the can in which the filler is bought. One coat usually suffices. However, if an especially smooth surface is desired a second coat may be applied in a similar manner.

After the filler has hardened, a very thin coat of shellac is to be put on. When this has dried, it should be sanded lightly and then one or two coats of wax should be properly applied and polished. Directions for waxing are upon the cans in which the wax is bought. A beautiful dull gloss so much sought by finishers of modern furniture will be the result of carefully following these directions.

A Hanger for Trousers

Secure two clothes pins of the metal spring kind for the clamps of the hanger. The pins are fastened one to each end of a looped galvanized wire. This wire should be about 6 in. long after a coil is bent in the center as shown in the sketch. The diameter of the wire should be about 1/8 in.

How to Make an Adjustable Negative Washer

The sketch herewith shows a washing box for negatives made from an ordinary wooden box. As can be seen, the grooved partition, A, is removable, and as several places are provided for its insertion, the tank can be made to accommodate anyone of several sizes of plates, says Camera Craft. The other stationary partition, B, which does not reach quite to the bottom of the tank, is placed immediately next to the end of the tank, leaving a channel between the two for the inflow of the wash water. A narrow, thin strip, C, is fastened to the bottom of the tank to keep the plates slightly raised, at the same time allowing a clearer flow of the water from the bottom upwards to the discharge.

The water enters the narrow partition at the end, flows under the partitions B and A, then upward between and parallel to the surface of the plates, escaping at the opposite end over the top of the tank end, in which the upper part has been cut away for that purpose. The depth of this cut, in the upper part of the tank end, should allow the overflow to be a trifle higher than the width of the largest size plate for which the tank is fitted. Partition B being stationary, can be nailed in position permanently, allowing the bottom edge to clear the bottom of the tank the desired distance. Partition A being movable should have attached to its bottom edge a couple of nails, D, or better still, wooden pegs, which will keep it also above the bottom of the tank at the desired height.

A coat of paraffin paint should be applied, and, just before it sets perfectly hard, any rough spots trimmed down with a knife or chisel and a second lighter coat applied. If the wood is very dry and porous a preliminary coat of the paint should be applied and allowed to soak into the pores. It is also well to apply a coat of the paint to the joints at the corners and around the edge of the bottom before nailing together.

Turn-Down Shelf for a Small Space

The average amateur photographer does not have very much space in which to do his work. The kitchen is the room used ordinarily for finishing the photographs. In many instances there will not be space enough for any extra tables, and so a temporary place is prepared from boxes or a chair on which to place the trays and chemicals. Should there be space enough on one of the walls a shelf can be made to hang down out of the way when not in use. A shelf constructed on this order may be of any length to suit the space or of such a length for the purpose intended. A heavy piece of wood, about 1-1/2 in. thick, and 4 to 6 in. wide, is first fastened to the wall at the proper height with nails, or, much better, large screws.

The shelf is cut and planed smooth from a board 12-in. wide and about 1-in. thick. This board is fastened to the piece on the wall with two hinges as shown in Fig. 1. A small cleat is nailed to the outer and under edge of the board and in the middle as shown. This is used to place a support under the outer edge of the shelf. The support, A, Fig. 2, should be long enough to extend diagonally to the floor or top of the baseboard from the inner edge of the cleat when the shelf is up in its proper place.

L. L.

Home-Made Electric Battery Massage

A simple and cheap electric massage device can be made by using three or four cells of dry battery connected to two ordinary silver tablespoons, as shown in the sketch. The handles of the spoons should be insulated or the operator can wear either kid or rubber gloves.

How to Make Tint Lantern Slides

Purchase some lantern slide plates and fix them in hypo without exposing, in the usual manner, same as you would an exposed plate, says the Moving Picture World. This leaves a thin, perfectly transparent emulsion film on the glass, which will readily take color. Mix a rather weak solution of clear aniline dye of the desired color and dip the plate in it, wiping the plate side clean. If not dark enough, dip again and again until desired tint is attained, letting it dry between each dipping. A very light blue tint slide will brighten a yellow film considerably, but the tint must be very light, just a bare tint.

A Bicycle Catamaran

The accompanying photographs show a bicycle boat made to carry two persons. This boat is constructed by using two galvanized iron tubes 18 ft. long and 12 in. in diameter, tapered at the front end down to cast-iron points, and the rear end shaped to attach rudders. These tubes are placed 26 in. apart, giving the boat an extreme width of 50 in.

The cylinders support a platform and on the rear end of this platform is constructed a paddle wheel 52 in. in diameter with 16 spokes. On the end of each spoke is fastened a galvanized sheet metal blade 6 in. wide and 8 in. long. A large guard placed over the paddle wheel forms a seat for one person and a chair in front on the platform provides a place for a second person.

The person in front helps to propel the boat with hand levers which are connected with rods to sprocket wheels on each side of the platform. The occupant of the rear seat contributes his part of the power with his feet on pedals of the shaft that carries the sprocket wheels. This shaft and sprocket wheels drive the paddle wheel by side chains of the bicycle kind. The boat is steered from the rear seat by ropes attached to double rudders. This boat will run at considerable speed and is very steady in rough water as it goes directly through large waves instead of going over them.

Contributed by Ernest Schoedsack, Council Bluffs, Iowa.

How to Make a Lead Pencil Rheostat

Take an ordinary lead pencil and cut seven notches at equal intervals on the pencil down to and around the lead, leaving it bare. A seven-point switch is constructed on a board of suitable size making the points by using screws that will go through the board. A small piece of tin or brass will do for a switch and is fastened as shown. The connections are made on the back side of the board as shown by the dotted lines. This will reduce 40 to 50 volts down to 5 or 10 volts for short lengths of time.

Contributed by Roy Newby, San Jose, Cal.

Homemade Shoe Rack

The accompanying sketch explains how a boy can make his own shoe rack that can be placed on the wall in the clothes closet. Figure 1 shows the construction of the bottom to permit the dirt to fall through. Two boards, 9 in. wide and about 3 ft. long, with six partitions between, as shown, will make pockets about 6 in. long. The width of the pockets at the bottom is 2 in. and at the top 5 in.

Contributed by Guy H. Harvey, Mill Valley, Cal.

How to Waterproof Canvas

The method used by the British navy yards for waterproofing and painting canvas so it will not become stiff and cracked is as follows: One ounce of yellow soap and 1/2 pt. of hot water are mixed with every 7 lb. of paint to be used. The mixture is applied to the canvas with a brush. This is allowed to dry for two days and then a coat of the same paint, without the soap, is laid on. When this last coat is dry the canvas may be painted any color desired. After three days of drying the canvas may be folded up without sticking together, and is, of course, waterproof. Canvas waterproofed in this manner makes an excellent covering for portable canoes and canvas boats. The color mixture for the soap and second application is made from 1 lb. of lampblack and 6 lb. of yellow ocher, both in oil; the finish coat may be any color desired. When no paint is to be used on the canvas it may be waterproofed with a mixture made from soft soap dissolved in hot water, and a solution of iron sulphate added. Iron sulphate, or ferrous sulphate, is the green vitriol. The vitriol combines with the potash of the soap, and the iron oxide is precipitated with the fatty acid as insoluble iron soap. This precipitate is then washed, dried and mixed with linseed oil.

Building a House in a Tree Top

The accompanying photograph shows a small house built in a tree top 20 ft. from the ground. The house is 5 ft. wide, 5 ft. 1 in. long, and 6 ft. 6 in. high. A small platform, 2 ft. wide, is built on the front. Three windows are provided, one for each side, and a door in front. The entrance is made through a trap door in the floor of the house. This house was constructed by a boy 14 years old and made for the purpose of watching over a melon patch.

Contributed by Mack Wilson, Columbus, O.

How to Make a Lamp Stand and Shade

A library light stand of pleasing design and easy construction is made as follows: Square up a piece of white oak so that it shall have a width and thickness of 1-3/4 in. with a length of 13 in. Square up two pieces of the same kind of material to the same width and thickness, but with a length of 12 in. each. Square up two pieces to a width and length of 3 in. each with a thickness of 1-1/8 in.

If a planing mill is near, time and patience will be saved by ordering one piece 1-3/4 in. square and 40 in. long, two pieces 1-1/8 in. thick and 3 in. square, all planed and sandpapered on all surfaces. The long piece can then be cut at home to the lengths specified above.

The 13-in. piece is for the upright and should have a 1/2-in. hole bored the full length through the center. If the bit is not long enough to reach entirely through, bore from each end, then use a red-hot iron to finish. This hole is for the electric wire or gas pipe if gas is used.

The two pieces for the base are alike except the groove of one is cut from the top and of the other from the under side, as shown. Shape the under sides first. This can best be done by placing the two pieces in a vise, under sides together, and boring two holes with a 1-in. bit. The center of each hole will be 2-1/2 in. from either end and in the crack between the pieces. The pieces can then be taken out, lines gauged on each side of each, and the wood between the holes removed with turning saw and scraper steel.

The width of the grooves must be determined by laying one piece upon the other; a trysquare should be used to square the lines across the pieces, however, gauge for depth, gauging both pieces from their top surfaces. Chisel out the grooves and round off the corners as shown in the sketch, using a 3/4-in. radius.

These parts may be put together and fastened to the upright by means of two long screws from the under side, placed to either side of the 1/2-in. hole. This hole must be continued through the pieces forming the base.

The braces are easiest made by taking the two pieces which were planed to 1-1/8 in. thick and 3 in. square and drawing a diagonal on each. Find the middle of this diagonal by drawing the central portion of the other diagonal; at this point place the spur of the bit and bore a 1-in. hole in each block.

Saw the two blocks apart, sawing along a diagonal of each. Plane the surfaces on the saw cut smooth and sandpaper the curve made by the bit. Fasten the braces in place by means of roundhead blued screws.

To make a shade such as is shown in the illustration is rather difficult. The shade is made of wood glued up and has art glass fitted in rabbets cut on the inner edges. Such shades can be purchased ready to attach. The sketch shows one method of attaching. Four small pieces of strap iron are bent to the shape shown and fastened to the four sides of the upright. Electric globes—two, three or four may be attached as shown.

The kind of wood finish for the stand will depend upon the finish on the wooden shade, if shade is purchased. Brown Flemish is obtained by first staining the wood with Flemish water stain diluted by the addition of two parts water to one part stain. When this is dry, sandpaper the "whiskers" which were raised by the water and fill with a medium dark filler. Directions will be found on the filler cans. When the filler has hardened, apply two coats of wax.

The metal shade as shown in the sketch is a "layout" for a copper or brass shade of a size suitable for this particular lamp. Such shades are frequently made from one piece of sheet metal and designs are pierced in them as suggested in the "layout." This piercing is done by driving the point of a nail through the metal from the under side before the parts are soldered or riveted together. If the parts are to be riveted, enough additional metal must be left on the last panel to allow for a lap. No lap is needed when joints are soldered.

A better way, and one which will permit the use of heavier metal, is to cut each side of the shade separately and fasten them together by riveting a piece of metal over each joint. The shape of this piece can be made so as to accentuate the rivet heads and thus give a pleasing effect.

For art-glass the metal panels are cut out, the glass is inserted from the under side and held in place by small clips soldered to the frame of the shade. Pleasing effects are obtained by using one kind of metal, as brass, and reinforcing and riveting with another metal, such as copper.

Illuminating a Watch Dial at Night

This picture shows a watch holder, with a device to receive an ordinary electric pocket lamp and battery. The battery is set in a bracket under which a reflector extends downward to throw the light on the dial of the watch and to protect the eyes from the direct light. The entire stand and bracket are made from sheet metal. The base is formed to make a tray to hold pins and collar buttons. It is not necessary to seek in the darkness for a push button or switch, as in ordinary devices, but a light pressure with the palm of the hand will make the lamp glow.

Home-Made Photographic Copying Stand

The difficulties of bad lighting on small articles can be entirely avoided by the use of a suitable support for the camera, the object and the background. For illustrations it is often an advantage to show an object with a perfectly plain background and no deep shadows. When using the stand as illustrated this is a very simple matter. Figure 1 shows the side, and Fig. 2 the front view of this stand. The stand is very easily constructed from pipe and pipe fittings. The main pipe of the stand will need to be of proper length to suit the focus of your camera. This can be determined by finding the length from the lens to the object after the bellows are extended to their full length. The arms holding the glass, as shown in the sketch, should be set at a point about the middle of the main tube. The cross that holds the middle arms should be 3/4 in. one way and 1/2 in. the other. This will allow for adjustment of the glass table. A small set screw provided in the back of this cross will hold the table in any position desired. The pipes and other connections are all 1/2-in. and the lengths of the pipes are made suitable for the size of the camera. When a small object is to be photographed it is placed upon the glass table and the background fastened to the board. In this manner small objects can be photographed without any deep shadow on one side. The bottom cross and ells should be corked so as to prevent any slipping and damage to the floor.

Home-Made Pocket Lamp

A simple and safe pocket lamp that will last for about 6 months without extra expense can be made at home for a few cents.

Have your druggist take a strong vial of clear glass, or a pill bottle with screw or cork top and put into it a piece of phosphorus about the size of a pea and fill the bottle one-third full of pure olive oil that has been heated for 15 minutes—but not boiled. Cork tightly and the result will be a luminous light in the upper portion of the bottle. If the light becomes dim, uncork and recork again. The lamp will retain its brilliancy for about 6 months. This makes a perfectly safe lamp to carry. These lamps are used by watchmen of powder magazines. Care should be exercised in handling the phosphorus, as it is very poisonous.

How to Make a Tangent Galvanometer

Secure a piece of wood 1/2 in. thick and cut out a ring with an outside diameter of 10-1/2 in. and an inside diameter of 9 in. and glue to each side two other rings 1/4 in. thick with the same inside diameter as the first ring and 11 in. outside diameter, thus forming a 1/4-in. channel in the circumference of the ring. If a lathe is at hand this ring can be made from a solid piece and the channel turned out. Cut another circular piece 11 in. in diameter for a base. Make a hole in the center of this piece 1 in. wide and 6-5/16 in. long, into which the ring first made should fit so that its inner surface is just even with the upper surface of the baseboard. The ring is held upright in the hole by a small strip screwed to the base as shown. All screws and brads that are used must be of brass. The cutting of these circular pieces is not so difficult if a band saw driven by power is used. They can be cut by means of a key-hole saw if a band saw is not accessible.

Before mounting the ring on the base, the groove should be wound with 8 turns of No. 16 double cotton-covered magnet wire. The two ends may be tied together with a string to hold them temporarily.

Fasten two strips of wood 1/4-in. thick 5/8-in. wide and 11 in. long across the sides of the ring with their upper edges passing exactly through the center of the ring. An ordinary pocket compass, about 1-1/4 in. in diameter, is fitted in these strips so that the center of the needle or pointer will be exactly in the center of the ring and its zero point mark at the half-way point between the two strips. Put the ring in place on the base, as shown in the sketch, and connect the two ends of the wire to two binding-posts that are previously attached to the base. Coat the entire surface with brown shellac. Any deviation from the dimensions will cause errors in the results obtained by its use.

Remove all pieces of iron or steel and especially magnets in the near vicinity of the instrument when in use. Place the galvanometer on a level table and turn it until the needle, pointing north and south, and swinging freely, lies exactly in the plane of the coil, as shown in the cut. The needle then will point to zero if the directions have been followed closely. Connect one cell of battery to the instrument and allow the current to flow through the coils. The needle of the compass will be deflected to one side or the other, and will finally come to rest at a certain angle-let us say 45 deg. The dimensions of the instrument are such that when the deflection is 45 deg. the current flowing through the coils upon the ring is 1/2 ampere. The ampere is the unit chosen to designate the strength of the electric current. For other angles the value of the current may be found from the following table:

Angles
Degrees Current
Amperes

10 .088

20 .182

30 .289

40 .420

45 .500

50 .600

55 .715

60 .865

70 1.375

As the magnetic force that acts upon a magnet needle varies in different places the values given for the current will not be true in all parts of the country. The table gives correct values for the immediate vicinity of Chicago and that part of the United States lying east of Chicago, and north of the Ohio river. The results given should be multiplied by 1.3 for places south of the Ohio river and east of the Mississippi.

Home-Made X-Ray Instrument

Two cylinders, AA, are mounted on a base, B, and mirrors, CC, are fitted at an angle of 45 deg. into these cylinders. Corresponding mirrors, EE, are put in the base parallel with those in those cylinders. An opening extends downward from D of each cylinder so that light entering at one end of the cylinder is reflected down at right angles by the first mirror to the second, from the second to the third, from the third to the fourth which reflects the light to the eye. Thus the light never passes through the cylinders and the observer does not see through, but around any object inserted at X between the cylinders.

How to Make a a Non-Polarizing Battery

Bichromate batteries are very expensive to maintain and dry cells do not furnish enough amperage for some kinds of experimental work. A cell of a battery that will run 10 hours with an output of over 1 ampere can be made as follows: Secure a jar about 4 in. in diameter and 8 in. high and place in the bottom of this jar the lower half of a tin baking powder can, to which a wire has been soldered for connections. Place in the can a mixture of 2 oz. black oxide of copper, 1 oz. black oxide of manganese and some iron filings.

Purchase a small crowfoot zinc and hang it about 1 in. above the half can. Prepare a 10 per cent solution of caustic soda and fill the jar within 1 in. of the top. Place on top the solution a thin layer of kerosene or paraffin. The cell will only cost about 50 cents to make and 25 cents for each renewal. When renewing, always remove the oil with a siphon.

Contributed by Robert Canfield, University Park, Colo.

A Home-Made Barometer

Take 1/4 oz. of pulverized camphor, 62 gr. of pulverized nitrate of potassium, 31 gr. nitrate of ammonia and dissolve in 2 oz. alcohol. Put the solution in a long, slender bottle, closed at the top with a piece of bladder' containing a pinhole to admit air, says Metal Worker. When rain is coming the solid particles will tend gradually to mount, little crystals forming in the liquid, which otherwise remains clear; if high winds are approaching the liquid will become as if fermenting, while a film of solid particles forms on the surface; during fair weather the liquid will remain clear and the solid particles will rest at the bottom.

Lock Lubricant

A door lock may be lubricated by using some lead scraped from the lead in a pencil and put in the lock. This may be done by putting the scrapings on a piece of paper and blowing them into the lock through the keyhole.

Rust Proofing Bolts

Where bolts are subject to rust, the threads should be painted with pure white lead; then they will not rust fast.

Painting Yellow Pine

When painting yellow pine exposed to the weather add a little pine tar with the priming coat.

Revolving a Wheel with Boat Sails

A novel windmill or revolving wheel can be made by placing a light wheel so it will turn freely on the end of a post, and placing four small sailing boats at equal points on the rim of the wheel. It makes no difference which way the wind blows, the wheel will revolve in one direction. In Fig. 1 the direction of the wind is shown by the arrows, and how the sails catch the wind and cause the wheel to revolve. Figure 2 shows how the wheel will appear when complete. This device makes an attractive advertising sign.

A Floating Electromagnet

A piece of iron placed in a coil of wire carrying a current of electricity becomes an electromagnet. If such a coil and iron core be made small enough they can be attached to a cork and the cork, floating on a solution, will allow the magnet to point north and south. The sketch shows how to make such an instrument. A coil of insulated wire is wrapped around a small iron core, leaving a few inches of each end free for connections. The insulation is removed from these ends and they are run through a piece of cork. Attach to the wires, on the under side of the cork, a piece of zinc to one end and a piece of copper to the other. The cork is then floated on a solution of acid, with the zinc and copper hanging in the solution. If zinc and copper are used, the solution is made from water and blue vitriol. If zinc and carbon are used, the solution is made from sal ammoniac and water.

The float will move about on the solution until the magnet iron will point north and south. If two of them are floating on the same solution, they will move about and finally arrange themselves end to end with the coils and magnet cores pointing north and south.

Contributed by C. Lloyd Enos.

A Fish Bait

A very effective fish bait is made by inclosing a live minnow in a short section of glass tube, which is filled with water and both ends closed with corks. This is used in place of the spoon.

Homemade Air Thermometer

The illustration shows the complete thermometer. The water in the glass tube is caused to rise and fall by the expansion and contraction of the air in the tin box.

A paper-fastener box, about 1-1/4 in. deep and 2 in. in diameter will serve very well for the box A. Solder in the side of the box 1-in. piece of 1/4-in. brass tubing, B, and then solder on the cover, C, so that the only escape for the air is through the brass tube. Secure a piece of 1/4-in. glass tubing—not shorter than 18 in.—and bend it as shown at D in the sketch. Hold the part of the tube to be bent in the broad side of a gas jet, and in a minute or two the tube will bend with its own weight. Any angle can be given glass tubing in this way. Connect the glass tube to B with a short piece of rubber hose, E. If the hose is not a tight fit, bind with a short piece of fine copper wire. The standard, F, is made from a piece of No. 10 wire about 10 in. long. To this standard solder the supporting wire, G—No. 14 wire will do. On one side bend the wire around the tube B, and on the other around the glass tube, D.

The base, H, can be made of oak, stained and varnished. The bottom of the box, A, is covered with lampblack so as to readily absorb all heat that strikes the surface. The black should not be put on until just before you paint the supports, cover and rim of the box with gold or silver paint. Hold the bottom of the box to be blackened over a little burning cotton saturated with turpentine.

The scale on the glass can be etched with hydrofluoric acid, or made with a little black paint. The water can be put in with a medicine dropper. This instrument will measure the amount of heat given by a candle some 20 or 30 ft. away.

Contributed by J. Thos. Rhamstine.

Home-Made Battery Voltmeter

Secure a piece of brass tube 3 in. long that has about 1/4-in. hole. Put ends, A, 1-1/4 in. square and cut from heavy cardboard on this tube. Make a hole in the center of each cardboard just large enough to allow the brass tube to fit tight. Put on two or three layers of stout paper around the brass tube and between the cardboard ends. Wind evenly about 2 oz. of No. 26 cotton covered magnet wire on the paper between the ends and leave about 2 in. of wire on each end extending from the coil. Use a board 1/2-in. thick, 3 in. wide and 6 in. long for the base and fasten the coil to it, as shown in Fig. 1. Bore holes for binding-posts, B, one on each side of the board, and connect the two wires from the coil to them. At the other end of the board and in the center drive a wire nail and attach a small spring, C, to it. The spring should be about 1 in. long. Take a small piece of soft iron, D, 1/2-in. long and just large enough to slip freely through the brass tube and solder a piece of copper wire to it; the other end of the copper wire being hooked to the spring, C. The copper wire must be just long enough to allow the piece of iron, D, to hang part way in the end of the coil and still hold the spring in place. A circular piece of cardboard, E, is slipped over the spring to where the spring joins the wire. This cardboard is to serve as the pointer. A piece of paper 1-1/2 in. wide and 2-1/2 in. long is glued to the board so that it will be directly under the cardboard pointer and fit snugly up against the top of the coil.

The paper can be calibrated by connecting one cell of battery to the binding-posts. The iron plunger, D, is drawn into the tube and consequently the pointer, E, is drawn nearer to the coil. Make a mark directly under the place where the pointer comes to rest. At the place mark the number of volts the cell reads when connected with a voltmeter. Do the same with two or three cells and mark down the result on the scale. By dividing off the space between these marks you may be able to obtain a surprisingly correct reading when connected with the battery cells to be tested.

Contributed by Edward M. Teasdale, Cuba, N. Y.

How to Make a Folding Canvas Cot

All the material required to make the cot as shown in Fig. 1 consists of wood 1-1/2 in. square of which two pieces are 6 ft. long; two pieces 2 ft. 3 in. long; two pieces 2-1/2 ft. long; four pieces 1-1/2 ft. long; four hinges; some sheet metal and 2-1/4 yd. of 8-oz. canvas.

Make a rectangle of the two long pieces and the two 2-ft. 3-in. pieces of wood as shown in Fig. 2, nailing well the corners together and reinforcing with a strip of sheet metal as shown in Fig. 3. The four pieces 1-1/2 ft. long are used for the legs, and two of them are nailed to one of the pieces 2-1/2 ft. long, making a support as shown in Fig. 5.

Make two of these—one for each end. The hinges are attached as shown in Fig. 5 and the whole support is fastened just under the end pieces of the frame by hinges. Four pieces of sheet metal are cut as shown in Fig. 4 and fastened to the body of the frame with their lower ends hooking over pins driven in each leg at the proper place. The canvas is stretched as tight as possible over the two long side pieces and fastened on the outside edge of each piece with large headed tacks. The legs will fold up as shown by the dotted line and the cot can be stored in a small space.

Contributed by R. J. Smith, Milwaukee, Wis.

How to Make a Small Geissler Tube

At first this would seem to be a difficult piece of work, yet a good and beautiful Geissler tube can be made at home in the following manner:

Procure a glass tube about 3-1/2 ft. long having a hole through its center about 1/8 or 1/4 in. in diameter, about 1 in. of No. 30 platinum wire and enough mercury to fill the tube and a small bowl. About 1-1/2 lb. of mercury will be sufficient. The first thing to do is to seal 1/2 in. of platinum wire in one end of the tube. This is done by holding the end of the tube with the right hand and taking hold of the tube with the left hand about 4 in. from the right hand. Hold the tube in a flame of a bunsen burner in such manner that the flame will strike the tube midway between the hands, as shown in Fig. 1, and keep turning the tube so as to get an even heat. When the glass becomes soft, remove the tube from the flame and quickly draw it out into a fine thread. Break this thread off about 1/8 in. from the long part of the tube and the end will appear as shown in Fig. 2. Take 1/2 in. of the platinum wire and slip it through the fine hole made by breaking the glass thread so that one-half of the wire will be inside of the long tube. If the end of the tube is now placed in the flame of the burner, the glass will adhere to the platinum wire and the wire will thus be sealed in the tube. The finished end will appear as shown in Fig. 3. This tube as described will be 8 in. long, although nearly any size could be made in the same way.

Measure 8 in. from the sealed end and place the tube at that point in the flame, holding in the left hand. At the same time take the piece of glass that was broken off at the end in the first operation and hold it in the flame with the right hand. When both the tube and piece of glass are soft, touch the soft part of the tube with the end of the glass and draw the tube out into a point like that shown in Fig. 4. Break off the piece of glass, thus leaving a small aperture in the long tube. Seal the remaining 1/2 in. of platinum in this aperture in the same manner as before being careful not to heat the tube too suddenly. The tube is now ready for filling and the upper part will appear as shown in Fig. 5.

The air is expelled from the tube by filling with mercury. This may be done by making a paper funnel and pouring the mercury slowly into the tube through the funnel. When the tube is filled to within 1/2 in. of the funnel remove the funnel and tap the side of the tube gently in order to remove any small air bubbles that may be clinging to the sides of the tube. The air bubbles will rise and come to the top. The tube now must be filled completely, expelling all the air. Place a finger over the end of the tube to keep the mercury in and invert the tube and set the end in the bowl of mercury. The mercury in the tube will sink until the level will be at about 30 in., leaving 8 in. of vacuum at the top. The next operation is to seal the tube at the half-way point between the lower platinum wire and the mercury level.

As the lower end of the tube must be kept at all times in the bowl of mercury until the tube is sealed, an assistant will be necessary for this last operation. Have the assistant hold the tube in the mercury at a slight angle, using care to always keep the lower end in the mercury, while you hold the burner in the left hand and allow the flame to strike the tube at the stated point. The part of the tube above this point will gradually bend over of its own weight as the glass softens. When it reaches the angle of about 60 deg., Fig. 6, take hold of the tube with the right hand still keeping the flame on the tube, and gradually draw the softened portion out until it separates from the main tube.

The tube is now finished and when the platinum wires are attached to the terminals of a spark coil a beautiful blue light will appear in the tube with a dark space at the negative end or cathode.

Contributed by David A. Keys, Toronto, Can.

Loosening Rusted Nuts

Nuts that are rusted fast can often be loosened by giving a hard turn in the tightening direction.

Cleaning Greasy Stoves

Greasy stoves may be cleaned with a strong solution of lye or soda.

How to Make a Take-Down Background Frame

Many amateur photographers who desire to do portrait work at home have left the subject alone for the want of a suitable background. A frame such as is used by the professional is entirely out of the question in most homes, says a correspondent of Camera Craft. The frame as shown in the sketch was devised and its chief advantage lies in the fact that when not in use it can be compactly tied together and stored away in a closet.

Almost any wood may be used in constructing this frame, but yellow pine is the best, as it is easily obtained and at the same time very well suited for such work. All pieces are to be dressed on all sides.

Two upright pieces are cut from 3/4 in. material 2 in. wide and 5 ft. 9 in. long and two blocks are fastened on the ends of each that are to be used for the bottom, as shown in Fig. 1. These blocks are each 2 by 6-in. and 1/4 in. thick. The base is made from a piece 3/4 in. thick, 3 in. wide and 5 ft. 4 in. long. A crosspiece 3/4-in. thick, 3 in. wide and 12 in. long, cut in the shape shown in Fig. 2, is screwed on each end of the base with 3-in. wood screws, as shown in Fig. 3. Four blocks 1/4 in. thick, 1 in. wide and 3 in. long are nailed to the sides of the base piece parallel with and at a distance of 2 in. from the end of same. This forms a slot, Fig. 4, to receive the pieces nailed to the ends of the uprights. To secure a rigid frame it is essential that this, joint be accurately put together.

Procure a piece of thick tin or brass and make two pieces like the pattern shown in Fig. 5, with each projection 3-in. long. The width of the crosspiece is 1 in. and the single projection 3/4 in. These are bent and nailed, one on each end of a piece of wood that is 1/4 in. thick, 1 in. wide and 5 ft. long, as in Fig. 6. These will form two pockets that will fit over the tops of the uprights. The frame is put together as shown in Fig. 7. Any background that will hang straight without need of being stretched can be hung on this frame.

Home-Made Kite Reel

This kite reel is constructed from two old pulleys and a few pipe fittings. The large pulley is about 14 in. in diameter, on the face of which are riveted flat strips of iron with extending arms. These arms are reinforced by riveting smaller pieces from one to the other, which connects all arms together on both sides of the wheel. Mounted on the shaft with the pulleys is a guide for the kite wire or string. The photograph shows that this guide permits of being moved entirely over the top of the reel. The smaller pulley is attached to the shaft and used as a brake. The brake is used only when running out the wire or string, first removing the crank.

Attaching Runners to a Bicycle for Winter Use

Instead of storing away your bicycle for the winter, attach runners and use it on the ice. The runners can be made from 1/4-in. by 1-in. iron and fastened to the bicycle frame as shown in the sketch. The tire is removed from the rim of the rear wheel and large screws turned into the rim, leaving the greater part of the screw extending. Cut off the heads of the screws and file them to a point. The rear runners should be set so the rim of the wheel will be about 1/2 in. above the runner level.

Contributed by C. R. Welsh, Manhattan, Kan.

A Paper That Makes Green Prints

A coating for ordinary paper that is said to give green prints is made with a two per cent solution of gelatine, says Photography, and sensitized with the following solution:

Potassium Bichromate 15 gr.

Magnesium Sulphate 15 gr.

Water 1 oz.

This mixture is spread over the paper in the usual way and the paper dried in the dark. Printing is carried rather far. The print is washed, then surface dried or blotted off on a pad and laid film upwards on a sheet of glass, and the following developer is applied with a wad of cotton wool wrung out:

Pyrocatechin 5 gr.

Water 1 oz.

The picture assumes a rich green color when developed, and is then washed for five or ten minutes and dried quickly by heat.

Copies Made from Wax Molds by Electro-Deposition

Fine copies of wax impressions can be made in the following manner: Procure an ordinary tumbler and fill it with a strong solution of sulphate of copper, which is made by dissolving two cents' worth of blue vitriol in 1/2 pt. of water. After this is done make a porous cell by rolling a piece of brown paper around a stick and fastening the edge with sealing wax; also, fix a bottom to the cell in the same way. Make a solution of one part of oil of vitriol [sulfuric acid] and 5 parts of water and pour this mixture into the porous cell. Wind the end of a copper wire around the end of a piece of zinc and place the zinc in the porous cell. Attach the other end of the wire to the wax impression.

The wax impression is made by pouring melted beeswax on the article you wish to reproduce and removing after the wax gets cold. The wax mold then should be coated with black lead and polished. This is done with a camel's hair brush. A fine copy can be made on the wax impression after the battery has been running about 12 hr.

Contributed by Edward M. Treasdale.

How to Make Skating Shoes

Remove the clamp part, as shown in Fig. 1, from an ordinary clamp skate. Drill holes in the top part of the skate for screws. Purchase a pair of high shoes with heavy soles and fasten the skates to the soles with screws, as shown in Fig. 2. When completed the skating shoes will have the appearance shown on Fig. 3. These will make as good skating shoes as can be purchased, and very much cheaper.

Contributed by Wallace C. Newton, Leominster, Mass.

How to Make a Self-Setting Rabbit Trap

Secure a good-sized box, say, 1 ft. high, 1-1/2 ft. wide, and 3 ft. long; and to the bottom, about 10 in. from one end, fasten a 2-in. square piece, A, Fig. 1, extending the width of the box. Place a 10-in. board sloping from the end of the box to the cleat A. The swing door B, Fig. 1, is made as shown in Fig. 2, which represents the back side of the door. Sheet metal or tin is cut to the proper size and tacked around the edge of the hole. This prevents the animal from gnawing its way out, also provides a way to make the hole of different sizes for squirrels or other animals. The hole in the door should be about 2 in. wide and 4 in. high for rabbits. The door is made to swing freely on two large nails driven through the sides of the box. The hole in the door being only large enough to admit a small portion of the rabbit's head, the rabbit will push its way through to the bait, causing the door to swing back and up, and it will close by its own weight when the animal is inside. A small door is provided in the other end to remove the animals caught.

The advantage of this trap is that where one animal is caught others are liable to follow, and several rabbits will be trapped at a time. Then, too, the rabbits are not harmed in any way as they would be if caught in an ordinary trap.

Contributed by H. F. Church, Alexandria, Va.

How to Make an Atomizer

Secure a good-sized test tube and fit it with a cork. Take two glass tubes, with about 1/8-in. hole, and bend them as shown in the sketch. This is done by heating them at the proper point over a gas flame until they are soft. Two holes are bored through the cork and the bent tubes inserted in them, as shown in the sketch, so that one of the tubes will extend nearly to the bottom of the test tube and the other just projecting through the cork. The spray tube may be made with a fine hole by first securing a tube longer than necessary and heating it at the proper point and drawing the tube out into a fine thread. The thread is broken off at the proper place to make a small hole.

Home-Made Kits for the Camera

If you have a 5 by 7-in. camera and wish to use some 4 by 5-in. plates, make a few simple kits to hold the smaller plates and fit the larger holders, says Camera Craft. Take two pieces of pasteboard, A and B, black surfaced if possible, and exactly 5 by 7 in. in size. The piece A will form the back of the kit and should have an opening cut in the center 4 by 5 in. in size. Paste a piece of strong black paper, C, over the under side of it to keep the plate from falling through. Cut an opening in the other piece, B, but cut it 1/4 in. shorter. This opening, being 1/8 in. shorter at each end, will retain the plate in position and cut off only that small amount of plate surface when the plate is exposed in the camera. Cut a piece of thin black cloth, D, 1 in. wide and 5 in. long. Lay it down on a piece of newspaper and coat one side with gum or mucilage. Stand the two pieces of 5 by 7 in. black cards on end together so that they will be square and true and bind the other ends with the strip of cloth so as to form a hinge. The two cards form a thickness about equal to a thick glass plate, and go in the holder in the same way. Lay one of these kits down against the ground side of the focusing screen and draw a line around, inside of the opening. This will be a guide as to just what will be secured upon the smaller plate when the kits are used.

How to Make a Miniature Stage

A good smooth box, say 8 in. wide, 10 in. high and 12 in. long, will serve the purpose for the main part of this small theater. Cut two rectangular holes, Fig. 1, one in each end and exactly opposite each other. Place a screw eye about 1/2 in. from the edge on each side of these openings. Fit an axle in the screw eyes and fasten a spool to the middle of the axle. On one of the two spools attach another smaller spool, Fig. 2, to be used as a driving pulley. Cut out the front part of the box down to a level with the top of the spools. Connect the spools with a belt made from tape about 3/4 in. wide. On this belt fasten figures cut from heavy paper and made in the form of people, automobiles, trolley cars, horses and dogs. A painted scenery can be made in behind the movable tape. The front part of the box may be draped with curtains, making the appearance of the ordinary stage, as shown in Fig. 3. A small motor will run the spools and drive the tape on which the figures are attached.

Contributed by William M. Crilly, Jr., Chicago.

A Floating Compass Needle

When a thoroughly dry and clean sewing needle is carefully placed on the surface of water the needle will float even if the density of steel is 7 or 8 times that of water. A sewing needle thus floating upon water may be used as a compass, if it has previously been magnetized. The needle will then point north and south, and will maintain this position if the containing vessel is moved about; if the needle is displaced by force it will return to its position along the magnetic meridian as soon as the restraint is removed.

Home-Made Dog Cart

The accompanying photograph shows a boy with his "dogmobile." The photograph was taken when they were on a new pavement which had 2 in. of sand left by the pavers and a grade of 6 per cent. The machine is nothing more than a boy's rubber-tired wagon on which are mounted a box for a seat and a wheel steering device extending above and below the board of the wagon. The front wheels are guided by ropes attached from each end of the axle and a few turns around the lower end of the steering rod. A pair of shafts are attached to the rear, into which the dog is harnessed.

How to Make a Dry Battery Cell

Dry battery cells are composed of the same materials for the poles, but instead of the liquid commonly used a paste is formed by mixing sal ammoniac and other salts with water and packed in the cell so it cannot spill.

A cell of this kind can easily be made, and to make it the proper size a sheet of zinc 8-1/2 in. long and 6 in. wide will be required. This zinc is rolled into a cylinder 2-1/2-in. in diameter. This will allow for a lap of 5/8 in., which is tightly soldered only on the outside of the seam. Close one end of the cylinder by soldering a disk of zinc over it, making a watertight receptacle. All soldering should be done on the outside and none of the solder allowed to run on the inside of the seam. All seams on the inside should be painted with asphaltum in order to cover any particles of solder. Do not paint any surface, only the joints. Secure three carbon rods 1/2-in. in diameter and 6 in. long which are copper plated. Carbons used in arc lamps will do. File the rods to remove the copper plate, leaving about 1/2-in. of the plate at one end. Tie the three rods in a close bundle with the copper-plated ends together and make a contact with each rod by soldering a wire to the plated ends, allowing one end of the wire to project about 2 in. for a connection. The plated ends of the carbons should be covered with paraffin for about 1 in. This is done by immersing them in a dish of smoking hot melted paraffin until the pores are thoroughly saturated.

The salts for filling are 1/4 lb. zinc oxide, 1/4 lb. sal ammoniac, 3/4 lb. plaster of paris, 1/4 lb. chloride of zinc mixed into a paste by adding 1/2 pt. of water. Form a 1/2-in. layer of paste in the bottom of the cylinder and place the ends of the carbon rods on this with their plated ends up. Hold the rods in the center of the cylinder and put the paste in around the rods with a stick. Pack the paste in, closely filling the cylinder to within 3/4 in. of the top. This space at the top is filled with a mixture of 1/2 lb. of rosin and 2 oz. beeswax melted together. This wax seals the cell and prevents any evaporation. Connection is made to the zinc by soldering a wire to the outside of the cylinder.

How to Paraffin Wire

The following description of how to make an apparatus with which to paraffin wire as needed makes clear a method of construction that is simple and easy to put together in a short time. Secure a pan to be used for this purpose only; one that will hold about 1 qt. The details of the construction are given in the diagram, in which P is the pan; B is a base of 1 in. pine; S is the spool of wire supported near one end of the base by nailing on standards H and H; F is a spool, with narrow flanges, supported near the bottom of the pan by the standards T and T. These may be made of two short pieces of a roller fitted into the holes bored in the base; A is a block of 1-in. pine with a piece of leather tacked on one side. Four nails should be driven in the base just outside of the edge of the pan to keep it from sliding off the pan.

Bore a hole in the base between the two spools and pass the wire through this hole, under the spool in the paraffin, then through a small hole in the leather and a notch in the block A, and a notch between the base and the pan. Tie a string around the wire between the leather and the paraffin, making the knots so they will not pull through the hole in the leather. This makes the wire smooth, and by making the string tighter or looser you can regulate the thickness of the paraffin, says Electrician and Mechanic. Place the pan on the stove; when the paraffin is melted, pull out the wire as needed. To keep the pan from sliding place a flatiron or some other weight on it.

Uses of Peat

Peat is used in Germany for bedding, fodder, filter, fuel and packing purposes.

Scientific Explanation of a Toy

In a recent Issue of Popular Mechanics an article on "The Turning Card Puzzle" was described and illustrated. Outside of the scientific side involved herein I describe a much better trick. About the time when the expression "skidoo" first began to be used I invented the following trick and called it "Skidoo" and "Skidee," which created much merriment. Unless the trick is thoroughly understood, for some it will turn one way, for others the opposite way, while for others it will not revolve at all. One person whom I now recall became red in the face by shouting skidoo and skidee at it, but the thing would not move at all, and he finally, from vexation, threw the trick into the fire and a new one had to be made. Very few can make it turn both ways at will, and therein is the trick.

Take a piece of hardwood 3/8-in. square and about 9 in. long. On one of the edges cut a series of notches as indicated in Fig 1. Then slightly taper the end marked B until it is nicely rounded as shown in Fig. 2. Next make an arm of a two-arm windmill such as boys make. Make a hole through the center of this one arm. Enlarge the hole slightly, enough to allow a common pin to hold the arm to the end B and not interfere with the revolving arm. Two or three of these arms may have to be made before one is secured that is of the exact proportions to catch the vibrations right.

To operate the trick, grip the stick firmly in one hand, and with the forward and backward motion of the other allow the first finger to slide along the top edge, the second finger along the side and the thumb nail will then vibrate along the notches, thus making the arm revolve in one direction. To make the arm revolve in the opposite direction—keep the hand moving all the time, so the observer will not detect the change which the band makes—allow the first finger to slide along the top, as in the other movement, the thumb and second finger changing places: e. g., in the first movement you scratch the notches with the thumb nail while the hand is going from the body, and in the second movement you scratch the notches with the nail of the second finger when the hand is coming toward the body, thus producing two different vibrations. In order to make it work perfectly (?) you must of course say "skidoo" when you begin the first movement, and then, no matter how fast the little arm is revolving when changed to the second movement, you must say "skidee" and the arm will immediately stop and begin revolving in the opposite direction. By using the magic words the little arm will obey your commands instantly and your audience will be mystified. If any of your audience presume to dispute, or think they can do the same, let them try it. You will no doubt be accused of blowing or drawing in your breath, and many other things in order to make the arm operate. At least it is amusing. Try it and see.

Contributed by Charles Clement Bradley, Toledo, Ohio.

The foregoing article describing the "Skidoo-Skidee Trick" appeared in a recent issue of Popular Mechanics. I have been told that a similar arrangement is used by a tribe of Indians in the state of Washington, by the Hindoos in India, and one friend tells me that they were sold on the streets of our large cities many years ago.

This toy interested me so much that I have made an investigation into the causes of its action, and I think the results may be of interest.

To operate, one end of the notched stick is held firmly in the left hand, while with the right hand a nail or match stick is rubbed along the notched edge, at the same time pressing with the thumb or finger of the moving hand against the oblique face of the stick. The direction of rotation depends upon which face is pressed. A square stick with notches on edge is best, but the section may be circular or even irregular in shape.

The experiments were as follows:

1. A rectangular stick had notches cut on one face. When the pressure was applied upon a face normal to the first, no rotation resulted. If the pressure was upon an edge, rotation was obtained.

2. Irregular spacing of the notches did not interfere with the action. The depth of the notches was also unimportant, although it should be suited to the size of the nail for best results.

3. The hole in the revolving piece must be larger than the pin; if there is a close fit no rotation is obtained.

4. The center of gravity of the revolving piece must lie within the hole. If the hole is not well centered the trick cannot be performed.

5. If the stick be clamped in a vise no results are obtained; with this exception: if the stick has enough spring, and the end clamped is far enough away from the notched portion, the rotation may be obtained. The above experiments led me to the conclusion that the operation of the device is dependent upon a circular motion of the pin, and this was confirmed by the following experiments. The action is somewhat similar to swinging the toy known as a locust around with a slight circular motion of the hand, It is necessary to show here that a slight circular motion is sufficient to produce the result and, secondly, that such motion can be produced by the given movements of the hands.

6. A piece of brass rod was clamped in the chuck of a lathe, and a depression made in the end slightly eccentric, by means of a center punch. If the end of the pin is inserted in this depression, while the hand holding the other end of the stick is kept as nearly as possible in the axis of the lathe, rotation of the lathe will produce rotation of the revolving piece. Speeds between 700 and 1,100 r. p. m. gave the best results.

7. A tiny mirror was attached to the end of the pin, and the hand held in the sunlight so that a spot of sunlight was reflected upon the wall. The notches were then rubbed in the usual way. The spot of light upon the wall moved in a way which disclosed two components of motion, one circular and one due to the irregular movements of the hand holding the stick. Usually the orbit was too irregular to show a continuous and closed circular path, but at times the circular motion became very pronounced. It was observed and the direction of rotation correctly stated by a man who was unaware of the source of the motion.

The production of the circular motion can be explained in this way: When the rubbing nail comes to a notch the release of pressure sends the stick upward; this upward motion against the oblique pressure upon the (say) right hand side gives also a lateral component of motion towards the left. As the nail strikes the opposite side of the notch the stick is knocked down again, this motion relieves somewhat the oblique pressure from the right hand side, and, the reaction from the holding (left) hand moves the stick to the right slightly, so that it is back in the old position for the next upward motion. Thus a circular or elliptic motion is repeated for each notch, and the direction of this motion is the same whether the nail be rubbed forward or back. For oblique side pressure from the right (notches assumed upward), the motion of the stick and hence of the revolving piece will be counter-clockwise; if the pressure is from the left, it will be clockwise.

That the motion of the revolving piece is due to a swinging action, and not to friction of the pin in the hole, is proved by experiments 3 and 4.

Contributed by M. G. Lloyd, Ph.D., Washington, D. C.

Home-Made Lantern

The accompanying picture shows a lantern which can be made almost anywhere for immediate use. All that is needed is an empty tomato or coffee can, a piece of wire and a candle. Make a hole a little smaller than the diameter of a candle and about one-third of the way from the closed end of the can, as shown. A wire is tied around the can, forming a handle for carrying. This kind of lantern can be carried against almost any wind and the light will not be blown out.

Contributed by G. A. Sloan, Duluth, Minn.

A Study of Splashes

When a rough, or greasy, or dusty sphere falls into a liquid, the liquid is forced away from the sphere. If the sphere is quite smooth the liquid rises up around and enclosing it in a sheath says Knowledge and Scientific News.

Reproduced herewith are a series of photographs showing successive stages in the entry of a rough sphere into milk and water, and the resultant "basket splash." The diameter of this sphere was about 3/5 in., and the height of the fall about 6 in. Examination of the photographs shows that the liquid, instead of flowing over and wetting the surface of the sphere, is driven violently away, so far as can be seen from the photographs, the upper portion is, at first, unwetted by the liquid. The gradual thickening of the crater wall and the corresponding reduction in the number of its lobes as the subsidence proceeds is beautifully shown. Thereafter there rises from the depth of the crater an exquisite jet which in obedience to the law of segmentation at once splits up in its upper portion into little drops, while at the same time it gathers volume from below and rises ultimately as a tall, graceful column to a height which may be even greater than that from which the sphere fell.

How to Make a Stick Pin

A fine stick pin or button can be made from a new one-cent piece. Carefully file out all the metal around the Indian head and slightly round the edges. Solder a pin to the back of the head when it is to be used for a stick pin. If a collar button base is soldered to the back of the head instead of the pin it can be used for a button. These can be gold plated by a jeweler and then you will have a neat pin or button, or a good emblem for the Order of Redmen.

How to Make a Miniature Electric Locomotive

A miniature electric railway is a thing that attracts the attention of almost any person. The cost of a toy electric locomotive is beyond the reach of many boys who could just as well make such a toy without much expense and be proud to say they "built it themselves." The electric locomotive described herewith uses for its power a small battery motor costing about $1. The first thing to do is to make the wheels and axles. If one has no lathe, the wheels can be turned at some machine shop. Four wheels are made from a round bar of metal, as shown in Fig. 1. Each wheel is 1/4 in. thick and 1 in. in diameter, with a 1/16-in. flange and a 1/4-in. hole drilled in the center. Each pair of wheels is fitted on a 1/4-in. axle, about 2-5/8 in. long. One of the axles should be fitted with a grooved belt wheel, as shown. Make the frame from three pieces of heavy brass, as shown in Fig. 2.

The first piece, or main part of the frame, is made from brass, 3/4 in. wide and 16 in. long, bent into an oblong shape and the ends soldered or bolted together. If the ends are to be soldered, before doing so drill four 1/4-in. holes 1 in. from the ends and insert the ends of the axles. The other two pieces are 1/2-in. wide and of the dimensions shown in the sketch. These pieces are riveted in the middle of the oblong frame, each in its proper place. The motor is now bolted, bottom side up, to the top of the piece fastened to the frame lengthwise. A trolley, Fig. 3, is made from a piece of clock spring, bent as shown, and a small piece of tin soldered to the top end for a brush connection. A groove is made in the tin to keep the trolley wire in place.

The trolley wire is fastened to supports made of wood and of the dimensions given in Fig. 4. The trolley should be well insulated from the frame. The parts, put together complete, are shown in Fig. 5. Run a belt from the pulley on the motor to the grooved wheel on the axle, as shown in Fig. 6, and the locomotive is ready for running.

In making the connections the travel of the locomotive may be made more complicated by placing a rheostat and controlling switches in the line, so that the engine can be started and stopped at will from a distance and the speed regulated. Automatic switches can be attached at the ends of the line to break the circuit when the locomotive passes a certain point.

One connection from the batteries is made to the trolley wire and the other to a rail. The connection for the motor runs from one binding post to the trolley and this connection must be well insulated to avoid a short-circuit. The other binding-post is connected to the frame.

The cost of making the wheels and purchasing the track will not be over $1.50. The track can be made from strips of tin put in a saw cut made in pieces of wood used for ties. This will save buying a track.

Contributed by Maurice E. Fuller, San Antonio, Texas.

Demagnetizing a Watch

A test can be made to know if your watch is magnetized by placing a small compass on the side of the watch nearest the escapement wheel if the compass pointer moves with the escapement wheel the watch is magnetized. A magnetized watch must be placed in a coil that has an alternating current of electricity flowing through it to remove the magnetism. A demagnetizer can be made as shown in the illustration. Two end pieces for the coil are made as shown in Fig. 1 from 1/4-in. wood. These ends are fastened together, Fig. 2, with cardboard 3 in. long glued to the inside edges of the holes cut in them. Wind upon the spool thus formed about 2 lb. of No. 16 cotton-covered copper wire. As it will be necessary to place a 16-cp. lamp in series with the coil, both the coil and lamp can be mounted on a suitable base and connected as shown in Fig. 3. The current, which must be 110 volt alternating current, is turned on the lamp and coil and the magnetized watch slowly drawn through the opening in the center of the coil.

Contributed by Arthur Liebenberg, Cincinnati, O.

How to Make a Pocket Skate Sharpener

Secure a square file and break off a piece, Fig 1, the length of a paper clip, Fig. 2. Draw the temper in the ends of this piece of file, but do not heat the center. This can be done by wrapping a wet piece of cloth or asbestos around the middle and holding it in the jaws of a pair of tongs which will only leave the end uncovered and projecting from the tongs about 1/2 in. Hold this projecting end in a flame of a plumber's torch until it is a dull red. Allow this to cool slowly while in the tongs. When cold treat the other end in the same way. This will draw the temper in only the ends which are filed, as shown in Fig. 1, and holes drilled in them. Also drill a hole in each end of the spring on the paper clip to match those drilled in the piece of file. Fasten the file in the clip with small bolts, as shown in Fig. 3. When the file gets filled with filings it can be removed and cleaned. Place the runner of the skate in the clip and hold flat on the surface of the runner. If the piece of file is fitted to the same width as the skate runner the sides of the paper clip will hold the file level with the surface of the runner without any trouble. Push the clip back and forth until the skate is sharpened.

Old-Time Magic

Trick with a Coin in a Wine Glass

The accompanying sketch shows a trick of removing a dime from the bottom of an old fashioned wine glass without touching the coin. The dime is first placed in the bottom of the glass and then a silver quarter dropped in on top. The quarter will not go all the way down. Blow hard into the glass in the position shown and the dime will fly out and strike the blower on the nose.

Untying-a-Knot Trick

Tie a double knot in a silk handkerchief, as shown in the accompanying sketch and tighten the last tie a little by slightly drawing the two upper ends; then continue to tighten much more, pulling vigorously at the first corner of the handkerchief, and as this end belongs to the same corner it cannot be pulled much without loosening the twisted line of the knot to become a straight line. The other corner forms a slip knot on the end, which can be drawn out without disturbing the form, or apparent security of the knot, at the moment when you cover the knot with the unused part of the handkerchief.

When the trick is to be performed, tie two or three very hard knots that are tightly drawn and show your audience that they are not easy to untie. The slip knot as described then must be made in apparently the same way and untied with the thumb while the knot is in the folds of the handkerchief.

Gear-Cutting Attachment for Small Lathes

When in need of small gears for experimental or model machines the amateur usually purchases them, never thinking that he could make them on his own lathe. A small attachment can be made to fasten in the tool post of a lathe and the attachment made to take a mandrel on which to place the blank for cutting a gear. The frame is made from a 1/2 in. square iron bent as shown in the sketch with the projecting end filed to fit the tool post of the lathe. A pair of centers are fitted, one of which should have a screw thread and lock nut for adjustment in putting in and removing the mandrel. All the old clock wheels that can be found should be saved and used for index wheels.

All of these wheels should be fitted to one end of the mandrel. The blank wheel is put on the outer end of the mandrel and a clock wheel having the number of teeth desired placed on the other end. When the mandrel is put in between the centers a small pawl is fastened with a screw to the frame with its upper end engaging in a tooth of the clock wheel. One clock wheel will index more than one number of teeth on a blank wheel. For instance: if the clock wheel has 18 teeth it can be made to index 6, 9 or 18 teeth to the blank by moving the number of teeth each time 3, 2 and 1 respectively.

In the sketch, A shows the end of the cutter and B the side and the shape of the cutting tool. When the cutter A, which is in a mandrel placed in the centers of the lathe, has finished a cut for a tooth, the pawl is disengaged and the mandrel turned to another tooth in the clock wheel.

In order to get the desired height it is sometimes necessary to block up the lathe head and the final depth of the tooth adjusted by the two screws in the projecting end of the frame which rests on the rocker in the tool post. Should too much spring occur when cutting iron gears the frame can be made rigid by blocking up the space between it and the lathe bed.

The cutter mandrel is placed in the centers of the lathe, or should the lathe head be raised, a short mandrel with the cutter near the end can be placed in a chuck, and adjusted to run true. The frame holding the mandrel, gear blank and clock wheel is inserted in the tool post of the lathe and adjusted for depth of the cutter. The lathe is started and the gear blank fed on the cutter slowly until the tooth is cut. The pawl is released and the mandrel turned to the proper number of teeth and the operation repeated. In this manner gears 3 in. in diameter can be made on a 6-in. swing lathe.

Contributed by Samuel C. Bunker, Brooklyn, N. Y.

Wire Terminals for Battery Connections

Good connections on the end of wires for batteries can be made from cotter pins, Fig. 1, about 1-1/2 in. long. Each end of the wire is put through the eye of a cotter pin, twisted around itself and soldered. The connection and eye are then covered with tape as shown in Fig. 2. When connecting to batteries, spread the pin and push the parts under the nut with one part on each side of the binding-post. When the nuts are tightened the connection will be better than with the bare wire.

Contributed by Howard S. Bott.

Simple Arts and Crafts Leather Work

Very interesting and useful pieces of leather work can be done with nothing more for equipment than a cup pointed nail set such as carpenters use, and a nut pick.

The accompanying illustrations show some of the things that can be made. Beginning at the left and reading to the right they are: -Case for court-plaster, coin purse, lady's card case, eye glass cleaner or pen wiper (has chamois skin within). Second row:—Two book marks, note book, blotter back, book mark. Third row:—Pin ball (has saddler's felt between the two leather disks), tea cosey, gentleman's card case or bill book. Fourth row:—Needle or pin case, tea cosey, lady's belt bag, watch fob ready for fastenings.

Procure a piece of Russian calf modeling leather. (1.) Make on paper the design wanted. (2.) Moisten the back side of the leather with sponge or cloth with as much water as it will take yet not show through on the face side. (3.) Place the leather on some hard non-absorbent material, such as brass or marble. (4.) Place the paper design on the leather and, holding it in place with the left hand, trace the outline, of the object and the decorative design with the nut pick so as to make a V-shaped groove in the leather. (5.) Take the paper off and working on the leather directly make the grooves deeper. (6.) With the cup-pointed nail set stamp the background promiscuously. This is done by making an effort to hold the point of the set about 1/4 in. above the surface, at the same time striking light, rapid blows on the top with a hammer or mallet.

With such objects as coin purses and card cases, a sewing machine will be needed to fasten the parts together. An ordinary machine will do. Frequently the parts are fastened by punching holes and lacing through these with leather thongs or silk cord.

In making symmetrical designs such as are here shown, draw center lines across the required space, dividing it into as many parts as desired. Make free-hand one quarter of the design, if four parts are to be alike, or one-half of the design, if but two parts. Fold over along these center lines. Put a piece of double-surfaced carbon paper between the parts and trace over the design already drawn.

How to Make a Simple Still

A still to distill water can be made from a test tube, some heavy rubber hose, and an ordinary bottle. Secure a stopper for the test tube, and bore a hole through the center, into which fit a small piece of tube. The bottle is also fitted with a stopper containing a piece of tube, and both bottle and test tube connected with a rubber tube.

The test tube is partly filled with water and supported or held over an alcohol lamp. The bottle should stand in a basin of cold water. When the water in the test tube begins to boil the steam passes over to the bottle, where it condenses. The basin should be supplied with cold water as fast as it begins to get warm. The rubber tube will not stand the heat very long and if the still is to be used several times, a metal tube should be supplied to connect the test tube and bottle.

Homemade Mariner's Compass

Magnetize an ordinary knitting needle, A, and push it through a cork, B, and place the cork exactly in the middle of the needle. Thrust a pin, C, through the cork at right angles to the needle and stick two sharpened matches in the sides of the cork so that they will project downward as shown. The whole arrangement is balanced on a thimble with balls of wax stuck on the heads of the matches. If the needle is not horizontal, pull it through the cork to one side or the other, or change the wax balls. The whole device is placed in a glass berry dish and covered with a pane of glass.

Brighten White Paint

Add aluminum bronze to a white or light paint that is to be used for lettering on a dark ground.

Quartz Electrodes Used in Receiving Wireless Messages

Wireless messages have been received at Washington, D.C., from Key West, Florida, a distance of 900 miles, through a receiving instrument in which two pieces of quartz of different composition were used on the electrodes. In making an instrument of this kind the quartz can be purchased from a dealer in minerals. One piece must contain copper pyrites and the other zincites. The electrodes are made cupping to hold the minerals and each should have a screw adjustment to press the pieces of quartz in contact with each other. Connect as shown in the illustration, using a high resistance receiver.

Contributed by Edwin L. Powell, Washington, D. C.

How to Make a Glider By Carl Bates

A gliding machine is a motorless aeroplane, or flying-machine, propelled by gravity and designed to carry a passenger through the air from a high point to a lower point some distance away. Flying in a glider is simply coasting down hill on the air, and is the most interesting and exciting sport imaginable. The style of glider described in this article is known as the "two-surface" or "double-decked" aeroplane, and is composed of two arched cloth surfaces placed one above the other.

In building a glider the wood material used should be straight-grained spruce, free from knots. First prepare from spruce planks the following strips of wood. Four long beams 3/4 in. thick, 1-1/4 in. wide and 20 ft. long; 12 crosspieces 3/4 in. thick, 3/4 in. wide and 3 ft. long; 12 uprights 1/2 in. thick, 1-1/2 in. wide and 4 ft long; 41 strips for the bent ribs 3/16 in. thick, 1/2-in. wide and 4 ft. long; 2 arm sticks 1 in. thick, 2 in. wide and 3 ft. long; the rudder sticks 3/4 in. square and 8 ft long; several strips 1/2 in. by 3/4 in. for building the vertical and horizontal rudders. The frames for the two main surfaces should be constructed first, by bolting the crosspieces to the long beams at the places shown by the dimensions in Fig. 1. If 20-ft. lumber cannot be procured, use 10-ft. lengths and splice them, as shown in Fig. 3. All bolts used should be 1/8 in. in diameter and fitted with washers on both ends. These frames formed by the crosspieces should be braced by diagonal wires as shown. All wiring is done with No. 16 piano wire.

The 41 ribs may be nailed to the main frames on the upper side by using fine flat-headed brads 7/8 in. long. These ribs are spaced 1 ft. apart and extend 1 ft. beyond the rear edges of the main frames, as shown in Fig. 1. After nailing one end of a rib to the front long beam, the rib is arched by springing down the loose end and nailing to the rear beam. The ribs should have a curve as shown in Fig. 2, the amount of curvature being the same in all the ribs.

The frames of the main surfaces are now ready to be covered with cloth. Cambric or bleached muslin should be used for the covering, which is tacked to the front edge, stretched tightly over the bent ribs and fastened securely with tacks to the rear ends of the ribs. The cloth should also be glued to the ribs for safety. In the center of the lower plane surface there should be an opening 2 ft. wide and 4 ft. long for the body of the operator. Place the two main surfaces 4 ft. apart and connect with the 12 uprights, placed in the corner of each crosspiece and beam. The uprights are fastened by bolting to the crosspieces, as shown in Fig. 2. The whole structure is made strong and rigid by bracing with diagonal wires, both laterally and longitudinally.

The vertical rudder is to keep the machine headed into the wind and is not movable. This rudder is made of cloth stretched over a light wooden frame, which is nailed to the rudder sticks connecting to the main frame. The horizontal rudder is also made of cloth stretched over a light wooden frame, and arranged to intersect the vertical rudder at its center. This rudder is held in position and strengthened by diagonal wires and guy wires. The horizontal rudder is also immovable and its function is to prevent the machine from diving, and also to keep it steady in its flight. The rudders are fastened to the glider by the two rudder sticks, and these sticks are held rigid by diagonal wires and also by guy wires leading to the sides of the main frames as shown in Fig. 1. The two arm sticks should be spaced about 13 in. apart and bolted to the long beams in the center of the opening in the lower plane where the operator is to take his position.

The glider should be examined to see that the frame is not warped or twisted. The surfaces must be true or the machine will be hard to balance when in flight. To make a glide, take the glider to the top of a hill, get in between the arm sticks and lift the machine up until the arm sticks are under the arms as shown run a few steps against the wind and leap from the ground. You will find that the machine has a surprising amount of lift, and if the weight of the body is in the right place you will go shooting down the hillside in free flight. The landing is made by pushing the weight of the body backwards. This will cause the glider to tip up in front, slacken speed and settle. The operator can then land safely and gently on his feet. Of course, the beginner should learn by taking short jumps, gradually increasing the distance as he gains skill and experience in balancing and landing.

The proper position of the body is slightly ahead of the center of the planes, but this must be found by experience. The machine should not be used in winds blowing faster than 15 miles an hour. Glides are always made against the wind, and the balancing is done by moving the legs. The higher the starting point the farther one may fly. Great care should be exercised in making landings; otherwise the operator might suffer a sprained ankle or perhaps a broken limb. The illustration shows two lines of flight from a hilltop, the glider travels on the upper line caused by the body of the operator taking a position a little back of the proper place, and on the lower line he changes his position from front to back while flying, which causes the dip in the line.

Boys Representing the Centaur

This is a diversion in which two boys personate a Centaur, a creature of Greek mythology, half man and half horse. One of the players stands erect and the other behind him in a stooping position with his hands upon the first player's hips, as shown in Fig. 1. The second player is covered over with a shawl or table cover which is pinned around the waist of the first player. A tail made of strips of cloth or paper is pinned to the rear end of the cover. The first player should hold a bow and arrow and have a cloak thrown loosely over his shoulder, as shown in Fig. 2. Imitation hoofs of pasteboard may be made and fastened over the shoes.

Home-Made Ladle for Melting Babbitt

Secure a large sized old bicycle bell and rivet a heavy wire or strap iron on one side for a handle. When heated a little, hammer out the edge on one side for a lip to pour from. This makes a good ladle for melting small amounts of babbit or lead.

Contributed by L. M. Olson, Bellingham, Wash

How to Make a Flash Lamp

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 an 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

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

Removing Scissors from a Cord

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

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

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

Disappearing Coin

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

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

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

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

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

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

Cutting a Thread Inside of a Glass Bottle

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

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

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

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

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 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.

"6 Times 6" "10 Times 7"

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.

"12 Times 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.

"18 Times 18"

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

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

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 1-1/2 in. 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

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

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

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

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 left-hand 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

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 1/8 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

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

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

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 11 Jump No. 2 over No. 7.

Move 12 Jump No. 1 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

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

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

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

Punching the Holes
Completed Shade Pattern

Lay out 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

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

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

Gas pipe and fittings were used wherever possible in the making of the swing as shown in the photograph. The diagram 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 l/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

The Disappearing Coin

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

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

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

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

"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

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

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

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

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

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

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

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

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

How to Make a Sailing Canoe

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

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

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

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

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

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

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 0 0

13 0 0

Right ascension of Venus 2 10 0

Set hour circle
to before meridian 10 50 0

Again

hour minute second

At 1 hr. 30 min.
mean clock shows 5 20 0 siderial

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 planet is visible to the naked eye.

Electric Light Turned On and Off from Different Places

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.

Optical Illusion

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

How to Make a Bunsen Cell

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.

One Way to Cook Fish

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

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

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

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 cover the soldered joints.

Contributed by Peter J. Johnson, Clermont, Iowa.

Dripping Carburetor

If gasoline drips from the carburetor when the engine is not running, the needle valve connected with the float should be investigated. If the dripping stops when the valve is pressed down, the float is too high. If the valve keeps dripping, then it should be ground to a fit.

A Merry-Go-Round Thriller

As a home mechanic with a fondness for amusing the children I have seen many descriptions of merry-go-rounds, but never one which required so little material, labor and time, and which gave such satisfactory results, as the one illustrated herewith. It was erected in our back yard one afternoon, the materials being furnished by an accommodating lumber pile, and a little junk, and it has provided unlimited pleasure for "joy-riders," little and big, from all over the neighborhood. It looks like a toy, but once seat yourself in it and begin to go around, and, no matter what your age or size may be, you will have in a minute enough thrill and excitement to last the balance of the day.

The illustration largely explains itself, but a few dimensions will be a help to anyone wishing to construct the apparatus. The upright is a 4 by 4-in. timber, set 3 ft. in the ground with 8 ft. extending above. It is braced on four sides with pieces 2 in. square and 2 ft. long, butting against short stakes. The upper end of the post is wound with a few rounds of wire or an iron strap to prevent splitting. The crosspiece is 2 in. square, 12 ft. long, strengthened by a piece 4 in. square and 5 ft. long. These two pieces must be securely bolted or spiked together. A malleable iron bolt, 3/4 in. in diameter and 15 in. long is the pivot. On this depends the safety of the contrivance, so it must be strong enough, and long enough to keep firmly in the post. Drive this bolt in a 3/8-in. hole bored in the post, which will make it a sufficiently tight fit. Make the hole for the bolt very loose through the crosspiece, so that there will be plenty of "wobble," as this is one of the mirth-making features of the machine. Use a heavy washer at the head. The seats are regular swing boards, supported by a stout and serviceable rope. A 3/4 -in. rope is not too heavy. One set of ropes are passed through holes at the end of the crosspiece and knotted on top. The other set should be provided with loops at the top and slid over the crosspiece, being held in position by spikes as shown. This makes an easy adjustment. Seat the heavier of the riders on the latter seat, moving it toward the center until a balance with the lighter rider is reached. A rope tied to the crosspiece about 2 ft. from the center, for the "motive power" to grasp, completes the merry-go-round.

Put plenty of soap or grease between the crosspiece and upright. Be sure to have room for the ropes to swing out at high speed, with no trees or buildings in the way. The "wobble" mentioned will give an agreeable undulating motion, which adds greatly to the flying sensation. This will be found surprisingly evident for so small a machine. As there is no bracing, care must be taken to have the two riders sit at the same moment, or the iron bolt will be bent out of line. If it is to be used for adults, strong clear material only should be employed.

Contributed by C. W. Nieman.

How to Make and Fly a Chinese Kite

The Chinese boy is not satisfied with simply holding the end of a kite string and running up and down the block or field trying to raise a heavy paper kite with a half pound of rags for a tail. He makes a kite as light as possible without any tail which has the peculiar property of being able to move in every direction. Sometimes an expert can make one of these kites travel across the wind for several hundred feet; in fact, I have seen boys a full block apart bring their kites together and engage in a combat until one of their kites floated away with a broken string, or was punctured by the swift dives of the other, and sent to earth, a wreck.

The Chinese boy makes his kite as follows:

From a sheet of thin but tough tissue paper about 20 in. square, which he folds and cuts along the dotted line, as shown in Fig. 1, he gets a perfectly square kite having all the properties of a good flyer, light and strong. He shapes two pieces of bamboo, one for the backbone and one for the bow. The backbone is flat, 1/4 by 3/32 in. and 18 in. long. This he smears along one side with common boiled rice. Boiled rice is one of the best adhesives for use on paper that can be obtained and the Chinese have used it for centuries while we are just waking up to the fact that it makes fine photo paste. Having placed the backbone in position, paste two triangular pieces of paper over the ends of the stick to prevent tearing. The bow is now bent, and the lugs extending from the sides of the square paper are bent over the ends of the bow and pasted down. If the rice is quite dry or mealy it can be smeared on and will dry almost immediately, therefore no strings are needed to hold the bow bent while the paste dries.

After the sticks are in position the kite will appear as shown in Fig. 2. The dotted lines show the lugs bent over the ends of the bow and pasted down. Figure 3 shows how the band is put on and how the kite is balanced. This is the most important part and cannot be explained very well. This must be done by experimenting and it is enough to say that the kite must balance perfectly. The string is fastened by a slip-knot to the band and moved back and forth until the kite flies properly, then it is securely fastened.

A reel is next made. Two ends—the bottoms of two small peach baskets will do—are fastened to a dowel stick or broom handle, if nothing better is at hand. These ends are placed about 14 in. apart and strips nailed between them as shown in Fig. 4, and the centers drawn in and bound with a string. The kite string used is generally a heavy packing thread. This is run through a thin flour or rice paste until it is thoroughly coated, then it is run through a quantity of crushed glass. The glass should be beaten up fine and run through a fine sieve to make it about the same as No.2 emery. The particles should be extremely sharp and full of splinters. These particles adhere to the pasted string and when dry are so sharp that it cannot be handled without scratching the fingers, therefore the kite is flown entirely from the reel. To wind the string upon the reel, all that is necessary is to lay one end of the reel stick in the bend of the left arm and twirl the other end between the fingers of the right hand.

A Chinese boy will be flying a gaily colored little kite from the roof of a house (if it be in one of the large cities where they have flat-roofed houses) and a second boy will appear on the roof of another house perhaps 200 ft. away. Both have large reels full of string, often several hundred yards of it. The first hundred feet or so is glass-covered string, the balance, common packing thread, or glass-covered string. As soon as the second boy has his kite aloft, he begins maneuvering to drive it across the wind and over to the first kite. First, he pays out a large amount of string, then as the kite wobbles to one side with its nose pointing toward the first kite, he tightens his line and commences a steady quick pull. If properly done his kite crosses over to the other and above it. The string is now payed out until the second kite is hanging over the first one's line. The wind now tends to take the second kite back to its parallel and in so doing makes a turn about the first kite's string. If the second kite is close enough, the first tries to spear him by swift dives. The second boy in the meantime is see-sawing his string and presently the first kite's string is cut and it drifts away.

It is not considered sport to haul the other fellow's kite down as might be done and therefore a very interesting battle is often witnessed when the experts clash their kites.

Contributed by S. C. Bunker, Brooklyn, N. Y.

Home-Made Vise

An ordinary monkey wrench that has been discarded is used in making this vise. The wrench is supported by two L-shaped pieces of iron fastened with a rivet through the end jaw, and these in turn are bolted or screwed to the bench. The handle end is held down with a staple. The inside jaw is used in clamping and is operated with the thumb screw of the wrench. Two holes bored through the thumb piece will greatly facilitate setting up the jaws tightly by using a small rod in the holes as a lever.

The vise may be made into a swing vise if the wrench is mounted on a board which is swung on a bolt at one end and held with a pin at the other as shown in the illustration. Various holes bored in the bench on an arc will permit the board to be set at any angle.

Contributed' by Harry S. Moody, Newburyport. Mass.

Home-Made Changing Bag for Plate Holders

A good bag for changing plates and loading plate holders and one that the operator can see well to work in can be made by anyone on a sewing machine. Ten yards of black cambric or other black cloth and a little ruby fabric will be required. Take the cambric and fold it into 2-yd. lengths (Fig. 1) which will make five layers of cloth, tack or fasten the layers together so they will not slip and cut an 8-in. square hole in the middle of one half (Fig. 2) and sew the ruby fabric over the opening. Be sure and make the seam light-tight and have enough layers of ruby fabric so no white light can get in. Fold the cloth up so it will be 1 yd. square (Fig. 3) and sew up the edges to make a bag with one side open. Put a drawstring in the edge of the cloth around the open side and the bag is complete ready for use.

Take the holders and plate boxes in the lap and put the bag over the head and down around the body, then draw the string up tight. A bag made up in this manner is for use only for a short time. If it is necessary to do considerable work at a time, then a dust protector, such as mill men use, must be attached to a 3-ft. length of 2-in. rubber hose and the hose run through a hole in the bag. This will make it possible to work in the bag as long as you wish.

Contributed by Earl R. Hastings, Corinth, Vt.

Home-Made Asbestos Table Pads

Asbestos table pads to prevent the marring of polished table tops from heated dishes can be easily made at home much cheaper than they can be bought. Procure a sheet of asbestos from a plumbing shop and cut it in the shape of the top of your table. If the table is round, make the pad as shown in the illustration, cutting the circular piece into quarters. Cut four pieces of canton flannel, each the size of half the table top. Two of the asbestos pieces are used to make one-half of the pad. Place the two pieces with their edges together so they will form half a circle disk and cover both sides with a piece of the flannel and pin them in place. A binding of white cotton tape is then basted around the edges to hold all the pieces together until they are stitched on a sewing machine. A line of machine stitching is made all around the outside and through the middle between where the edges of the asbestos sheets join together. This will form a hinge so the two quarters may be folded for putting away. Make the other half circular disk in the same way. If leaves are wanted in extending the table, any number of pads can be made to cover them in the same manner with the hinge in the middle of each pad. The flannel is used with the nap side out so it will make the pad soft and noiseless. This kind of a pad furnishes perfect protection to the table from any heat or moisture.

Contributed by H. E. Wharton, Oakland, Calif.

How to Make a Ladies' Handbag

To make this bag, get a piece of Russian calf modeling leather. A shade of brown is the best as it does not soil easily and does not require coloring, which spoils the leather effect.

The dimensions of the full sized bag are: from A to B, 17-1/2 in.; from C to D, 16-1/4 in.; from E to F, 9-1/4 in.; G to H, 6-1/4 in., and E to G, 2-1/4 in.

Enlarge the accompanying pattern to the given dimensions, trace this or some other appropriate design on it, and then cut the leather the size of the pattern.

Use a sponge to dampen the leather on the rough side, not so damp that the water will come through to the right side when working, but damp enough to allow the design to be well impressed on the leather. Use a smooth, non-absorbent surface to lay the leather on while at work.

Now lay the pattern on the right side of the leather and with the smallest end of the leather tool or a sharp, hard pencil, trace the design carefully on the leather. Moisten the leather as often as necessary to keep it sufficiently moist to work well. Trace the openings for the handles, also lines A-G, H-B, and E-G, G-J, and corresponding lines on the other side.

Remove pattern and trace the design directly on leather with the round point of tool, until it is made distinct and in marked contrast to the rest of the leather. Do not make sharp marks but round the edges of the lines nicely, with the rounded sides of the tools.

To complete the bag, get something with which to make a lining. A piece of oozed leather is the most satisfactory. Cut it the same size as the bag, place both together and with a leather punch, make holes all around the edge of the bag about 1/2 in. apart. Cut out the leather for the handle openings. Care should be taken not to cut the holes too near the edge of the bag lest the lacing pull out. Now cut narrow thongs, about 1/8 in. wide, and lace through the holes, lacing the sides of the end pieces in with the sides of the bag. Crease the lines A-G and B-H inward for ends of bag.

Removing Wire Insulation

The claw of a hammer can be used for removing the insulation on copper wire, if not more than 1 in. is taken off at a time.

A Small Electric Motor

The drawing herewith shows a simple electric motor which can be easily constructed by any boy who is at all handy with tools. I made this motor many times when a boy and can say that if carefully constructed it will run with greater rapidity than the more expensive ones.

A common magnet which can be purchased at any toy store is used. The one shown is 3-1/2 in. in length. The armature core is a strip of 1/16 by 1/4-in. iron, 2-1/4 in. long, bent U-shaped and fastened to the wood flywheel. Each leg of the armature is wound with 10 ft. of No. 24 gauge magnet wire. The commutator is made from an old 22 cartridge filed into two equal parts, each being a half circle, both of which are made fast to a collar on the shaft E. Each half of the commutator must be insulated from the other half. The collar can be made by wrapping paper around the shaft until the required size is obtained.

The top end of the shaft runs in a hole bored in a brass support, B, which is screwed on the end of a piece of wood mortised in the base, as shown in Fig. 1. The lower end of the shaft runs in a glass bead, D, which is fastened to a small piece of brass with sealing wax. The small brass piece is fastened to the base with screws. The bead should not have an eye larger in diameter than the shaft. The shaft is made from an old discarded knitting needle. The brushes are fastened to each side of the upright piece of wood supporting the brass bearing B.

The connections to the battery are shown in Fig. 2. Each half of the commutator C is connected to the coils AA as shown in Fig. 1.

Contributed by J.M. Shannon, Pasadena, Calif.

Moving a Coin Under a Glass

Place a penny or a dime on a tablecloth, towel or napkin and cover it over with a glass in such a way that the glass will rest upon two 25 or 50 cent pieces as shown in the sketch. The coin is made to come forth without touching it or sliding a stick under the edge of the glass. It is only necessary to claw the cloth near the glass with the nail of the forefinger. The cloth will produce a movement that will slide the coin to the edge and from under the glass.

Improving Phonograph Sound

When playing loud and harsh records on a phonograph the music is often spoiled by the vibration of the metal horn. This may be remedied by buckling a valise or shawl strap around the horn, near the center.

How to Make Paper Balloons

Paper Balloon Pattern and Parts to Make Balloon

Balloons made spherical, or designed after the regular aeronaut's hot-air balloon, are the best kind to make. Those having an odd or unusual shape will not make good ascensions, and in most cases the paper will catch fire from the torch and burn before they have flown very far. The following description is for making a tissue-paper balloon about 6 ft. high.

The paper may be selected in several colors, and the gores cut from these, pasted in alternately, will produce a pretty array of colors when the balloon is in flight. The shape of a good balloon is shown in Fig. 1. The gores for a 6-ft. balloon should be about 8 ft. long or about one-third longer than the height of the balloon. The widest part of each gore is 16 in. The widest place should be 53-1/2 in. from the bottom end, or a little over half way from the bottom to the top. The bottom of the gore is one-third the width of the widest point. The dimensions and shape of each gore are shown in Fig. 2.

The balloon is made up of 13 gores pasted together, using about 1/2-in. lap on the edges. Any good paste will do—one that is made up of flour and water well cooked will serve the purpose. If the gores have been put together right, the pointed ends will close up the top entirely and the wider bottom ends will leave an opening about 20 in. in diameter. A light wood hoop having the same diameter as the opening is pasted to the bottom end of the gores. Two cross wires are fastened to the hoop, as shown in Fig. 3. These are to hold the wick ball, Fig. 4, so it will hang as shown in Fig. 5. The wick ball is made by winding wicking around a wire, having the ends bent into hooks as shown.

The balloon is filled with hot air in a manner similar to that used with the ordinary cloth balloon. A small trench or fireplace is made of brick having a chimney over which the mouth of the paper balloon is placed. Use fuel that will make heat with very little smoke. Hold the balloon so it will not catch fire from the flames coming out of the chimney. Have some alcohol ready to pour on the wick ball, saturating it thoroughly. When the balloon is well filled carry it away from the fireplace, attach the wick ball to the cross wires and light it.

In starting the balloon on its flight, take care that it leaves the ground as nearly upright as possible.

Contributed by R. E. Staunton.

A Simple Steamboat Model

The small boat shown in the accompanying sketch may have a length of 12 to 18 in. and is constructed in the following manner: A small steam boiler, A, is supported by two braces over an alcohol lamp in the middle of the boat. A small pipe is fastened to the top of the boiler in such a way that the open end will be opposite the open end of another pipe, B, somewhat larger in size. The pipe B opens into the stern of the boat at C, as shown in Fig. 1. The steam, coming through the small pipe A, is driven forcibly through the larger pipe B, and carries with it a certain amount of air out through the opening C into the water. As the boat is driven forward by this force, the steam arises to the surface in the form of bubbles. The boat soon attains considerable speed, leaving a long wake behind.

To Remove Grease from Machinery

A good way to remove grease or oil from machinery before painting is to brush slaked lime and water over the surface, leaving the solution on over night. After washing, the iron is dried and the paint will stick to it readily.

In removing grease from wood, common whitewash may be left on for a few hours and then washed off with warm water, after which the paint will adhere permanently.

A Game Played on the Ice

Two lines are drawn parallel on the ice from 50 to 100 ft. apart and blocks of wood are placed every 6 ft. apart on these lines. The player opening the game skates to the line and delivers, in bowling form, a sliding block similar to the blocks that are placed on the lines with the exception that it has a handle. The blocks are about 6 in. wide by 6 in. high and 8 in. long. The sliding blocks should be at least 1 ft. long and each provided with a handle. The handle is attached by boring a hole near one end in the middle of the block and driving in a wood pin. The hole is bored slanting so as to incline the handle. Two of these blocks are provided for the reason that when a player bowls one of the opposing player's blocks over the line he is entitled to another throw. The side wins that bowls over all of the opposing players' blocks first. This will prove an interesting and enjoyable pastime for skaters.

Making Photo Silhouette Brass Plaques

Secure a brass plate having a smooth surface the right size for the photograph and cover it with a coat of paraffin. This is done by heating the paraffin in a vessel hot enough to make the wax run freely, then pouring the liquid over the entire surface of the brass.

When the paraffin has cooled sufficiently the outlines of the photograph must be drawn upon its surface. There are three ways of doing this: First, the photograph can be traced on tissue paper and then retraced on the paraffin surface. The exact outlines of the photograph can be obtained this way without destroying the print. Second, if you have several copies of the photograph, one can be utilized by tracing direct to the surface of the paraffin. In using either of the two methods described, carbon paper must be placed on the paraffin before the tissue paper or photograph is laid upon it. Third, cut out the outlines of the photograph and lay it on the paraffin surface, then trace around the edges with the point of a needle or sharp point of a knife. The outlines drawn by the first method are cut through the paraffin in the same way. The paraffin is carefully removed from the inside of the lines, leaving the brass surface perfectly clean, as is shown in Fig. 1. The exposed part of the plate is now ready to be etched or eaten away to the right depth with acid. The acid solution is made up of 1-1/2 parts muriatic acid and 2 parts water. The mixture should be placed in a glass or earthenware vessel. If the plate is a small one a saucer will do for the acid solution. Pour the acid on the plate where the paraffin has been removed and allow it time to etch. The acid should be removed every five minutes to examine the etching. If any places show up where the paraffin has not been entirely removed they must be cleaned so the acid will eat out the metal. When the acid solution becomes weak new solution must be added until the proper depth is secured. Rinse the plate in cold water, stand in a tray and heat it sufficiently to run off all the paraffin. Polish the plate by rubbing it with a piece of flannel.

The plaque can be given a real antique finish by painting the etched part with a dull black paint. Drill a small hole in each of the four corners, being careful not to dent the metal. The plaque is backed with a piece of wood 3/4 in. thick, the dimensions of which should exceed those of the brass plate sufficiently to harmonize with the size of the plaque. The wood should be painted black with the same paint used in the plaque. Paint the heads of four thumb tacks black and use them in fastening the plaque to the board. The finished silhouette will appear as shown in Fig. 2.

Contributed by John A. Hellwig, Albany, N. Y.

Aligning Automobile Headlights

Automobile headlights should be set to throw the light straight ahead, not pointed down at the road at an angle.

Telescope Stand and Holder

Fig. 1 Fig. 2
Made of a Camera Tripod

With the ordinary small telescope it is very difficult to keep the line of sight fixed upon any particular object. To meet the situation I constructed the device illustrated herewith. A circular piece of wood, B, 6 in. in diameter, is fastened to a common camera tripod, A, with a set screw, S. Corner irons, CC, are screwed to the circular piece. These corner irons are also screwed to, and supported in a vertical position by the wood standard D, which is 4 in. wide and of any desired height. To this standard is secured the wood shield-shaped piece E by the screw G upon which it turns. A semi-circular slit is cut in the piece G, through which passes the set screw S. The telescope is secured to the piece G by means of the pipe straps FF. Rubber bands are put around the telescope to prevent rubbing at the places where the straps enclose it.

The wood pieces were made of 1/2 in. mahogany well rubbed with linseed oil to give them a finish. The corner irons and set screws or bolts with thumb-nuts can be purchased at any hardware store. The pipe straps of different sizes can be obtained from a plumber's or gas and steam fitter's store. With this device, either a vertical or a horizontal motion may be secured, and, after bringing the desired object into the line of sight, the set screws will hold the telescope in position. Anyone owning a tripod can construct this device in three or four hours' time at a trifling cost. In Fig. 1 is shown the side view of the holder and stand, and Fig. 2 the front view.

It may be of interest to those owning telescopes without solar eyepieces to know that such an eyepiece can be obtained very cheaply by purchasing a pair of colored eyeglasses with very dark lenses and metal rims. Break off the frame, leaving the metal rims and nibs at each end. Place these over the eyepiece of the telescope and secure in place with rubber bands looped over the nibs and around the barrel of the instrument.

Contributed by R. A. Paine, Richmond, Va.

How to Make an Electrical Horn

Secure an empty syrup or fruit can, any kind having a smooth flat bottom will do. If the bottom is not perfectly flat, it will interfere with the regular tone vibrations, and not produce the right sound. Remove the label by soaking it in hot water. Take an ordinary electrical bell and remove the gong, clip off the striking ball and bend the rod at right angles. Cut a block of wood 3/4 in. thick, 5 in. wide and 8 in. long for the base. Fasten the can on it with a piece of sheet brass or tin as shown in the sketch. Mount the bell vibrator on the base, using a small block of wood to elevate it to the level of the center of the can, and solder the end of the vibrator rod to the metal.

Connect two dry cells to the bell vibrator, and adjust the contact screw until a clear tone is obtained. The rapidly moving armature of the bell vibrator causes the bottom of the can to vibrate with it, thus producing sound waves. The pitch of the tone depends on the thickness of the bottom of the can. This horn, if carefully adjusted and using two cells of dry battery, will give a soft pleasant tone that can be heard a block away. If the two projecting parts of the vibrator are sawed off with a hacksaw, it can be mounted on the inside of the can. This will make a very compact electric horn, as only the can is visible.

Contributed by John Sidelmier, La Salle, Ill.

Driving a Washing Machine with Motorcycle Power

The halftone illustration shows how I rigged up my washing machine to be driven by the power from my motorcycle. I made a wheel 26 in. in diameter of some 1-in. pine boards, shrunk an iron band on it for a tire, and bolted it to the wheel on the washing machine. A long belt the same width as the motorcycle belt was used to drive the machine. The motorcycle was lined up and the engine started, then the motorcycle belt thrown off and the long belt run on, connecting the engine and washing machine wheel.

I. R. Kidder, Lake Preston, S. D.

Home-Made Aquarium

A good aquarium can be made from a large-sized street lamp globe and a yellow pine block. Usually a lamp globe costs less than an aquarium globe of the same dimensions. Procure a yellow pine block 3 in. thick and 12 in. square. The more uneven and twisted the grain the better for the purpose, it is then less liable to develop a continuous crack.

Cut out a depression for the base of the globe as shown in Fig. 1. Pour in aquarium cement and embed the globe in it. Pour more cement inside of the globe until the cement is level with the top of the block. Finish with a ring of cement around the outside and sprinkle with fine sand while the cement is damp. Feet may be added to the base if desired. The weight of the pine block makes a very solid and substantial base for the globe and renders it less liable to be upset.

Contributed by James R. Kane, Doylestown, Pa

Protect Your Lathe

Never allow lard oil to harden on a lathe.

Frame for Displaying Both Sides of Coins

It is quite important for coin collectors to have some convenient way to show both sides of coins without touching or handling them. If the collection consists of only a few coins, they can be arranged in a frame as shown in Fig. 1. The frame is made of a heavy card, A, Fig. 2, the same thickness as the coins, and covered over on each side with a piece of glass, B. Holes are cut in the card to receive the coins C. The frame is placed on bearings so it may be turned over to examine both sides. If there is a large collection of coins, the frame can be made in the same manner and used as drawers in a cabinet. The drawers can be taken out and turned over.

Contributed by C. Purdy, Ghent, O.

How to Make Lantern Slides

A great many persons who have magic lanterns do not use them very much, for after the slides have been shown a few times, they become uninteresting, and buying new ones or even making them from photographic negatives is expensive. But by the method described in the following paragraph anyone can make new and interesting slides in a few minutes' time and at a very small cost.