Part II--Construction

Transformers may be divided into two main groups, the classification being made according to the relation between the magnetic circuit of the transformer and the primary and secondary windings. When the two windings surround the magnetic circuit of a transformer, as indicated in Fig. 9, the transformer is said to be of core type. If the magnetic circuit surrounds the windings, as indicated in Fig. 10, the transformer is said to be of the shell type. The following instructions are for a shell-type transformer.

Any mass of magnetic material, such as a piece of soft iron, when placed in a magnetic field that is produced by an alternating current, will be rapidly magnetized and demagnetized, the rapidity of the change depending upon the frequency of the current producing the field. When a piece of iron is magnetized and demagnetized, as just stated, there will be a certain amount of heat generated in it and this heat represents energy that must come from the electrical circuit producing the magnetic field in which the iron is placed.

The heat that is generated in the iron is due to two causes: First, the hysteresis loss which is due to a property of the iron that causes the magnetism in the iron to lag behind the magnetizing influence, or the changes that are constantly taking place in the field strength due to the alternating current. This loss cannot be entirely eliminated, but it may be reduced to a very low value by using a soft grade of iron, or one having what is called a low hysteretic constant. Second, the eddy-current loss which is due to the circulation of currents through the mass of metal. These currents are due to unequal electromotive forces set up in the different parts of the piece of metal when there is a change in the strength of the field in which the metal is placed. This loss cannot be entirely eliminated, but it can be greatly reduced by breaking the mass of metal up into parts and insulating these parts from each other, which results in the paths in which the eddy currents originally circulated being destroyed to a certain extent.

The breaking up of the metal is usually made in such a way that the joints between the various parts are parallel to the direction of the magnetic field. When the joints are made in this way, they offer less opposition to the magnetizing force. This is one of the principal reasons why induction-coil cores are made up of a bundle of wires instead of a solid piece. These wires are annealed or softened to reduce the hysteresis loss that would occur. The combined hysteresis and eddy-current losses, which are spoken of as the iron losses, will of course be very small in the transformer you are going to construct, but the above discussion is given to show why the magnetic circuits of transformers are built up from sheets of soft iron, called laminations. The core is said to be laminated.

The dimensions of the complete magnetic circuit, of the transformer you are going to construct, are given in Fig. 11. The primary and secondary windings are both to be placed about the center portion C, and it is apparent that the winding of these coils would be very tedious if the wire had to be passed back and forth through the openings A and B. This procedure in winding can be prevented by first forming the part of the magnetic circuit upon which the windings are placed; then wind on the coils and, after they are completed, finish building up the magnetic circuit with pieces cut to the proper size and shape.

Procure a small quantity of soft, thin sheet iron and cut out a sufficient number of rectangular pieces, 3 in. by 4-1/4 in., to make a pile 3/4 in. in height when firmly pressed together. Now cut a rectangular notch in each of these pieces, 2 in. wide and 3-5/8 in. long. The sides of this notch can be cut with a pair of tinner's shears, and the end can be cut with a sharp cold-chisel. Be careful not to bend either piece any more than you can help. The outside piece, or the one in which the notch is cut, should have dimensions corresponding to those given in Fig. 12. When all of these pieces have been cut, as indicated above, the rectangular pieces, 2 in. by 3-5/8 in., that were cut out to form the notch in the larger pieces, should have two of their corners cut away, so as to form pieces whose dimensions correspond to those given in Fig. 13. These last pieces are to form the core and part of the end of the transformer. Now make sure that all the edges of the pieces are perfectly smooth and that they are all of the same size; then give each one a coat of very thin shellac.

Now cut from a piece of insulating fiber, that is about 1/16 in. thick, two pieces whose dimensions correspond to those given in Fig. 14. When these pieces are completed, the core of the transformer can be assembled as follows: Place the T-shaped pieces, whose dimensions correspond to those given in Fig. 13, through the openings in the pieces of insulation, alternate pieces being put through the openings from opposite sides. The distance from outside to outside of the pieces of insulation should be exactly the same as the length of the vertical portion of the T-shaped pieces forming the core, or 3 in.

Cut from some soft wood four pieces having cross sections whose dimensions correspond to those given in Fig. 15, and of such a length that they will just slip down between the two pieces of insulation. These pieces should now be placed on the four sides of the iron core and covered with several layers of heavy insulating cloth. Each layer of the cloth should be shellacked as it is put on, which will increase the insulation and at the same time help in holding the wooden pieces in place. You are now ready to start winding the transformer.

The secondary, which is the low-voltage side in this case, as you are using the transformer to reduce or step down the voltage, will have the smaller number of turns, and larger wire should be used in winding it than in the primary, as it will carry a larger current. On account of the secondary being of larger wire, it will be placed on the core first. For this winding you will need a small quantity of No. 26 B. & S. gauge, single cotton-covered wire. Drill a small hole through one of the insulating washers, down close to the cloth covering the core, being careful at the same time to keep the hole as far from the metal part of the core as possible. Pass the end of a short piece of No. 18 or 20 B. & S. gauge, double cotton-covered wire through this opening and solder it to the end of the No. 26 wire. Insulate the joint with a piece of paraffin paper or cloth, and bind the piece of heavy wire to the core of the transformer with a piece of linen thread.

Now wind the No. 26 wire on the core as evenly as possible, to within about 1/8 in. of the end of the spool. Place over the first layer two layers of paraffin paper and wind on a second layer of wire. Three layers should give you the required number of turns in the secondary winding and a resistance of approximately 3-1/2 ohms. The end of the secondary winding should be terminated in the same way as the winding was started. Outside of the completed secondary winding place at least six layers of paraffin paper, or several layers of insulating cloth. The paraffin paper used should be approximately five mills in thickness. You can make your own paraffin paper by taking a good quality of writing paper about two mills thick and dipping it into some hot paraffin, then hanging it up by one edge to drain.

The primary winding is to be made from No. 34 B. & S. gauge, single silk-covered copper wire. The inside end of this winding should be started in the same way as the secondary, but at the end opposite to the one where the secondary terminated. Wind about 240 turns on each layer and place one layer of paraffin paper between each layer of wire. The primary winding should have at least 12 layers, and the outside end should be terminated as the inside end. Outside of the completed windings, place several layers of insulating cloth to serve as an insulation, and at the same time provide a mechanical protection for the windings.

The outside part of the magnetic circuit can now be put in place. When the U-shaped pieces are all in place, the magnetic circuit will have the form and dimensions shown in Fig. 11. A clamp should now be made for each end of the transformer, to hold the pieces forming the magnetic circuit together, and at the same time give an easy means of mounting the transformer. Cut from a piece of sheet iron, about 1/16 in. in thickness, two pieces whose dimensions correspond to those given in Fig. 16, and two pieces whose dimensions correspond to those given in Fig. 17. Drill the holes in these pieces as indicated, and bend the larger ones into the form shown in Fig. 18. These pieces can now be clamped across the ends of the transformer with small bolts, as shown in Fig. 19.

A box should now be made from sheet iron to hold the transformer. The box should be of such dimensions that it will be at least 1/8 in. from the transformer at all points. This box should be provided with a cover that can be easily removed.

Now mount the transformer in the box by means of small bolts, that pass through the holes in the supports and holes in the bottom of the box. Two binding-posts can now be mounted on one end of the box, and insulated from it, to serve as terminals for the secondary winding. Two pieces of stranded No. 14 B. & S. gauge, rubber-covered copper wire should now be soldered to the terminals of the primary circuit and passed out through insulating bushings mounted in holes cut in the end of the box opposite to the one upon which the binding-posts were mounted. These heavy wires should be firmly fastened to the iron part of the transformer inside the box, so that any outside strain placed upon them will not, in time, break them loose from the smaller wires. Be sure to insulate all joints and wires well inside the box.

A circuit can now be run from a 110-volt lighting or power circuit, observing the same rules as though you were wiring for lights, and connected to the heavy wires, or primary circuit. The binding-posts, or secondary winding should be connected to the bell circuit and the transformer is complete and ready to operate. You may have to change the adjustment of the bells, but after a little adjustment they will operate quite satisfactorily.

Mirror Hinged to Window Casing

A shaving mirror is usually placed on a window sash to avoid shadows as much as possible. This is very inconvenient and many times the mirror is broken by a fall. A good way to avoid shadows and have the mirror handy is to hinge it to the window casing. This can be done with screweyes, A, and screwhooks, B. The screweyes are turned into the frame of the mirror and the screwhooks into the window casing. Two screwhooks can also be turned into the casing on the opposite side of the window, if desired, so that the mirror can be used on either side.--Contributed by James D. McKenna, New Britain, Conn.

A Cleaning Bath for Silverware

A good way to clean silverware of all coloring by eggs or other substances is to place the silver articles in a kettle of boiling water containing a few pieces of zinc. An electrolytic action is produced by the zinc, water and silver which decomposes the sulphides on the silver and leaves it well cleaned. No silver is taken away by this method.--Contributed by Loren Ward, Des Moines, Iowa.

To Prevent Poultry Water from Freezing

The method shown in the sketch is used by me in cold weather to keep the drinking water for the poultry from freezing. The device consists of a part of a barrel inverted and set over the fountain, and a tubular lantern. A small opening is cut in one side of the barrel through which the fowl can reach the water.--Contributed by P. C. Fish, Kansas City, Mo.

How to Make a Letter Scale

A reliable letter scale that can be easily made is shown in the sketch. It consists of a wide-neck bottle filled with water into which the weighing device is inserted. This latter part is made of a light piece of wood weighted on the lower end, to keep it in a stable, upright position, and a piece of cardboard is tacked to the other. The wood is placed in the water, and known weights are used on the cardboard while calibrating.

The first line is marked at the water level when there is no weight on the cardboard, and then a known weight placed on the top and another mark made at the water level, and so on, until a sufficient number of 1/2-oz. and ounce-divisions have been marked. The wood should be well coated with shellac varnish before it is placed in the water.--Contributed by Francis Chetlain, Chicago.

Summer Dish Washing

A labor-saving method in dish washing for a summer day is as follows: Construct a substantial wood frame and cover it with galvanized wire mesh. Attach legs and put it in a convenient place on the back porch. Wash the dishes on one end, and wipe the silverware dry. At the outer end spread a towel over the wire and place the dishes turned down upon it to dry, and cover them with another towel.--Contributed by L. Alberta Norrell, Tifton, Ga.

Nozzle Angle for Lawn Sprinkling

Where there is no prop or water sprinkler at hand for tilting the nozzle of a hose, start to tie a knot in the hose, as shown in the sketch, but do not draw it up tightly. The hose nozzle can be tilted to any angle in this manner.--Contributed by S. J. Eddy, Portland, Oregon.

Simple Methods of Connecting Call Bells

The following diagrams will indicate a few of the various methods that may be employed in connecting up electric bells for different purposes, A, B and C representing the push buttons; D, the bells; E, the batteries, and G, the ground. The simplest possible connection is shown in Fig. 1, the bell D, battery E, and push button A, are all connected in series. The operation of the bell is independent of the order in which the bell, battery, and push button are placed, so long as there is a complete circuit when the push button is pressed. One of the wires in this circuit may be done away with by completing the circuit through the ground, as shown in Fig. 2. Connecting a bell as shown in this diagram often results in quite a saving of wire. The proper connections for operating one bell from either of two push buttons, A or B, is shown in Fig. 3. Two bells, D, operated from a single push button, C, are connected as shown in Fig. 4. The two bells, D, are shown connected in parallel, which requires more wire than if they were connected in series. If they be connected in series, one or the other should have its make-and-break contact closed. The bell whose circuit remains unchanged will intercept the current for the other bell in series with it. The operating of the bells is more satisfactory, however, when they are in parallel, and each taking current from the battery independent of the other.

The diagram, Fig. 5, shows the proper connections for operating two bells from two independent push buttons, each push button operating a particular bell. Any number of bells operated from any number of push buttons, all of the bells being rung from any one of the push buttons, are connected as shown in Fig. 6. Such a circuit can be used as a fire alarm or time call in a factory, the operation of the circuit being controlled from any one of a number of different points.

The proper connections for what is called a return-call circuit is shown in Fig. 7. The circuit is so arranged that the bell at one end is controlled by the push button at the other end. Such a circuit can be used in transmitting signals in either direction. A ground return-call circuit is shown in Fig. 8. In the circuits shown in Figs. 7 and 8, only one battery is needed.

The connections of a two-wire metallic return-call circuit are shown in Fig. 9. A special push button must be used in this circuit, and in this case two batteries are used instead of one, as in Figs. 7 and 8. This circuit may be changed to a ground return-call circuit by using the earth as a conductor instead of either wire. There are, of course, numerous other methods that may be used in connecting call bells, but the connections shown in the diagrams are perhaps the most common.

Refrigerator for Dry and Warm Climates

Set a bowl containing butter, cream or fruit in a saucer and cover the bowl with a moistened napkin, allowing the edges to hang in a larger saucer filled with water, and place the whole in the air out of the sun's rays. The article to be kept cool may also be placed in a pan with an earthenware crock turned over it and covered with a small towel or cloth, the edges of which extend into another outer pan partly filled with water.

The method can be applied on a larger scale by using a shallow galvanized pan which will contain many articles and more water. This manner of cooling is especially adapted to camping parties and will prevent sloppy butter, sour milk and spoiling fruit. The articles are also kept free from ants and flies.--Contributed by C. B. Hosford, Swansea, Ariz.

Pencil-Sharpening Guide

The sketch shows how a guide for making a true point on a lead pencil may be made of a block of wood. The hole, which should be large enough to allow the pencil to be turned easily, is bored at the proper angle to form the desired point on the pencil. The long side of the block serves as a guide for the knife blade, while the projection at the bottom acts as a stop. The guide insures an even point and is easily manipulated. It is held in the palm of the left hand and the pencil is turned with the thumb and forefinger, while the knife is held against the face of the block, cutting edge downward, and worked up and down with the right hand.

Homemade Hinges

When making a chicken house recently I had forgotten to procure hinges. When searching the "junk" box I found some little metal brackets such as used for holding spring roller shades. Attaching these as shown, I made a good substitute hinge. A pair of the brackets having no slots were selected. A 2-1/2-in. wire nail with a washer was placed in the hole and driven into the top of the door, 1 in, from its back edge. The other bracket was placed on the bottom of the door in a similar manner. The door was placed in an open position and the prongs of the brackets were nailed to the door post. The bottom bracket may also be nailed to the floor and the top one to the lintel.--Contributed by Robert Smith, E. Burnaby, B. C.

Skimmer for Bottled Milk

The cream that rises on the milk in an ordinary milk bottle cannot be removed easily. Where a small family desires to use the cream for coffee, the skimmer shown in the sketch is very handy.

The cone is made of metal--tin, brass or copper--which can be nickelplated, the seam being soldered. The cone is 2 in. deep with a diameter at the top of 1-3/8 in. A handle can be made of a discarded sugar or teaspoon, which is soldered to the cone. Insert the cone in the bottle far enough for the cream to flow into it and then withdraw. Cream will gather about 3 in. deep on rich milk. The milk can be used for cooking. A piece of wire can be used for a handle instead of the spoon.--Contributed by Victor Labadie, Dallas, Texas.

How to Preserve Putty

Having some putty left over after a job of glazing and wishing to keep it without its becoming dried up, I tried wrapping it in paraffin paper such as used to wrap butter. I found this method to be a decided success, the oil being prevented from drying out.--Contributed by Levi R. Markwood, Fairview, Pa.

How to Build a Simple Electric Motor By A. G. McClure

An exceedingly simple and inexpensive motor that may be used in operating small toys can be constructed as follows: First procure a good permanent magnet, about 5 in. long and about 1-1/2 in. between the inside edges at the open end. This magnet should be at least 1/2 in. thick, and if it cannot be had in one piece, two or more may be placed side by side, like poles being placed together. The writer was unable to procure ready-made magnets, so one was formed and magnetized. Obtain a piece of tungsten or some other good-grade steel, 1/2 in. by 1/2 in., and about 11 in. long. Bend this piece into the form of a U, with the inner edges 1-3/4 in. apart. Square off both ends and drill two small holes in the outside surface of each end, at AA, about 3/8 in. from the end. Tap these holes for small machine screws. Drill the hole B with a small drill, about 1/16 in., in the center of the lower portion of the U and ream it out. The piece should now be clamped with a good pair of blacksmith's tongs,--a block of iron being placed between the ends to keep the pressure of the tongs from drawing them together--heated to a cherry red and then plunged into a bath of oil. It can then be magnetized by placing it in contact with a permanent magnet.

Next obtain a piece of 1/8-in. brass, about 1/2 in. wide and 5-1/2 in. long. Drill two holes in each end of the piece to match those drilled in the ends of the magnet, also one in the center, and tap it for a 1/8-in. machine screw. Now bend this piece into the form shown. Provide a machine screw, S, for the hole C and drill a small tapered hole in the end of the screw.

Obtain a small quantity of soft sheet iron and cut a sufficient number of pieces similar to that shown at D to make a pile 1/2 in high. Cut two pieces of the same size from some thin sheet brass. Now place all of these pieces in a pile, the brass pieces being on the outside, and clamp them securely, then drill the two small holes, E and F. Place two small copper rivets in these holes and rivet the heads down before removing the clamp. Drill a 1/8-in. hole, G, through this piece, the armature, for the shaft to pass through. Procure a piece of 1/8-in. steel rod, about 6 in. long. Sharpen one end so that it will enter the hole B, then cut the other end off and sharpen it so that it will enter the opening made in the end of the screw S. The armature may now be soldered to this shaft, its left-hand surface being flush with the ends of the magnet.

A small commutator, H, should now be made as follows: Obtain a piece of thin brass tubing about 5/8 in. in diameter. Turn down a piece of hard rubber so that the tube will fit tightly on it. Drill a hole in this piece of rubber of such a size that it will have to be forced on the steel shaft. Saw two longitudinal slots in the brass tube diametrically opposite each other and then bind these two pieces in place on the piece of rubber with some heavy linen thread wrapped around each end. The armature is now ready to wind. Get a small quantity of No. 22 gauge cotton-covered wire, solder one end to one of the segments of the commutator, then wind one end of the armature full and cross over and wind the other end full, soldering the end of the wire to the second commutator segment. Make sure to wind both ends of the armature in the same direction so the current in both parts of the winding produces magnetizing effects in the same direction. Insulate the winding from the core and the different layers from each other with a good quality of thin writing paper.

Two small brushes should now be made from some thin spring brass and mounted on the brass piece as shown. These brushes should be insulated from the piece of brass and two small binding posts should be provided for making connections to them. The position of the commutator and brushes should be such that the brushes move from one segment to the other when the ends of the armature are directly in line with the ends of the permanent magnet.

A small pulley should be mounted upon the shaft to be used in transmitting the power. The whole device may be mounted in a horizontal position on a wooden base as shown, and the motor is complete.

How to Make a Humidity Indicator

A simple weather indicator that may be used in determining the condition of the atmosphere may be made as follows: Dress a small figure, in the form of a doll, with a piece of cloth, previously dipped in the following solution: Chloride of cobalt, 30 parts by weight; sodium chloride, 15 parts; gum arabic, 7-1/2 parts; calcium chloride, 4-1/2 parts, and water, 400 parts. This cloth will change color as the amount of moisture in the atmosphere changes, the change being due to the cobalt salt, which, in dry air, is lavender blue. As the moisture in the atmosphere increases, the color changes first to bluish red, then light red and finally pink, according to the amount of moisture. With a decrease in moisture, the colors change in the reverse order to that given above, and the blue color returns when the air becomes dry.

The "Q" Trick

Lay out the form of the capital letter Q with coins on a table and ask someone in the audience to select a number and then ask that person to count up from one until the number is reached, beginning at A and stopping on the circle, for instance at B, then counting back again beginning with one, but, instead of counting on the tail, pass it and go around the circle, say, to C. The performer gives these instructions to the person doing the counting. The one selecting the number must not tell the performer what the number is, and the latter is to leave the room while the counting proceeds. The performer, before leaving the room, is to tell which coin will be the last one counted.

Take, for example, the number 7. Counting from A to B there are just 7 coins and counting back the last number or 7 will be at C. Try 9 for the number and the last one counted will also be C. The number of coins in the tail represents the number of coins in the circle from the intersection of the tail and circle to the last number counted. For instance, the sketch shows 4 coins in the tail, therefore the last coin counted in the circle will be at C or the fourth coin from the intersection of the tail and circle.

By slipping another coin in the tail the location of the last coin counted is changed, thereby eliminating any chance of exposing the trick by locating the same coin in the circle every time. This can be done secretly without being noticed.

To Keep Ants Away From Food

Suspend a shelf, breadbox or rack with wire around which is tied a piece of cotton cloth, saturated with a mineral oil. The ants will not cross the oil-soaked cloth.

Some strong wire hooks attached to the rack or shelf answer well to hang small articles on, such as bacon, bags of sugar, syrup cans, etc.--Contributed by C. B. Hosford, Swansea, Ariz.

Vaulting-Pole Holder

An adjusting device for a vaulting pole that can be easily fixed at any point on a round pole by using a wedge and ring, is shown in the sketch. The wedge carries a pin on which to place the cross pole. The manner of using this device as well as its construction is clearly indicated.--Contributed by Sterling R. Speirs, St. Louis, Mo.

Flying Model Aeroplane for a Display

A novelty for a window display is made of a model aeroplane flying by its own power. To control the direction and make the model fly in a circle it is fastened to a long stick or beam which is pivoted in the center. The one shown was pivoted to a roller-skate wheel which in turn was fastened to a metal standard. The beam was attached to the skate wheel with two small bolts which were insulated and carried two brushes as commutator contacts.

The commutator rings were made of heavy brass strips, fastened to a round piece of wood which was attached to the metal standard. The wires from the current supply were connected to the commutator rings. From the brushes connecting wires were carried along the beam to the aeroplane motor which was a small battery motor with propeller.

The opposite end of the beam was weighted to balance it. The first sketch shows the parts and the manner of making the connections. The aeroplane is driven in a circular path by its own power in a realistic manner.

An Electric Time Light

Although the modern alarm clock is a wonderfully effective piece of mechanism, it is, to say the least, very abrupt in its manner. It seldom confines its efforts to the chamber of its owner, but spreads its disturbance all over the building. It is very easy for a person to arise early in the summer and no greater difficulty should be experienced in winter, if the bedroom is brightly lighted at the proper hour. To do this simply and automatically became the problem.

The first thought was to obtain one of those clock-actuated electric-light switches, such as the stores use, but this would not do, because it meant some unsightly wiring around the room. It was then remembered how, in the course of some experiments, an ordinary incandescent light was operated through a piece of No. 36 gauge wire without any sign of heating. If, then, a wire only 1/200 in. in diameter were of ample carrying capacity, surely a dollar watch would be sufficient to make the connection. Such being the case, the whole mechanism could readily be attached to the drop cord of a lamp directly above the socket, thus obviating any additional wiring. This all proved to be true, and the whole was made and attached in the course of a couple of hours.

While one might feel enthusiastic about this small and easily contrived affair, it is scarcely to be presumed that it would operate so effectively on one who had spent the larger part of the night tripping the "light fantastic," or in undue conviviality. An ordinary 16-cp. globe has thus far operated perfectly, and a 40-watt tungsten lamp would, if not too far away, surely awaken the hardest sleeper of sober habits.

The base of the mechanism is a small piece of 1/4-in. hard wood, upon which is fastened a small brass bracket, A, bent so as to hold the watch from slipping down. A small clip, B, was then arranged so as to grip the neck of the watch after its lower edge had been placed against A, and a small brad at either side prevented lateral movement. In this way the watch was held firmly, yet in a manner that would permit its being taken out instantly when necessary. The glass and minute hand were removed. The brass bolt from an exhausted dry cell was placed at C, so as to clamp a small copper washer to which was soldered a narrow strip of copper, D, about 1/16 in. wide and cut from a leaf of an old dynamo brush. This strip is arranged so as to wipe the hour hand as it travels past, but being so thin, it has no appreciable effect on the time keeping. As illustrated, the device is set for six o'clock, but by loosening the nut C an hour's adjustment either way may be had. It is a very simple matter, however, to arrange the device so it will operate at any hour. In connecting up, one end of the drop cord is removed from the socket and attached to A, which throws the current through the watch, thence along the hand and down D to C, from where it is carried by a short piece of wire to the socket again. As there are so many circuits through the watch, the small current required for one light does not affect it in any way. Thus far, no trouble has been experienced in making this delicate connection with 110 volts, but if any should develop, the contacts may be tipped with the small pieces of platinum taken from a burned-out globe.

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The meat of a white English walnut may be easily removed by heating the nut in an oven or on top of a stove, then using a knife to pry the shell open.

A Small Shocking Machine

An amusing as well as instructive shocking machine, usually called a medical coil, can be easily constructed from a discarded buzzer or electric bell, four binding posts, some pieces of insulated wire, two carbon rods, and a rheostat.

A base for attaching the parts is made of a piece of poplar, 10 in. long, 5 in. wide, and 1/2 in. thick, which can be finished as desired, but a good method is to shape the edge like molding and give it a mahogany stain, and when dry apply a coat of white shellac, which should be allowed to dry a day, whereupon the surface is rubbed with prepared wax. When the base is ready, mount the buzzer at one end. This can be easily done by making an L-shaped piece of metal, A, which is fastened to the base with a screw, and to the yoke of the magnet coil with a small bolt. If the armature and its connections are also used from the buzzer, the height of the coils must be taken in consideration. These parts are fastened in position as shown, using an L-shaped piece of metal, B, for the spring end. The screw holding the armature spring to the base, as well as the vibrator screw, should be of such a length that it will enter the base far enough to permit a connection for a wire in a countersunk hole bored in the base from the under side. Binding posts are placed in the corners of the base in holes countersunk from the under side for the screw heads.

The rheostat is of the miniature-battery type, which has a round base and a coil of resistance wire with a lever passing over the coil. Such a rheostat can be purchased from an electrical store, but if the person constructing the shocking machine desires to make one, it is not difficult if a lathe is at hand.

To make the rheostat, turn up a disk, about 3 in. in diameter, from a piece of hard wood, such as oak, maple, or walnut, and form a circular groove in the upper surface, about 3/8 in. inside of the circumference. The groove is to admit a circular coil of resistance wire, and in making it, be sure to have it the proper size to take the coil snugly. The coil can be of any size, and to make it, resistance wire is wound around a piece of wire used as a mandrel. If the coil is 1/4 in., or a trifle smaller, in diameter, it will make a good size. Be sure that the depth of the groove is such that it will allow a part of the coils of the resistance wire to project above the surface of the wood disk. The coil of wire should be just long enough to fit in the groove and allow a 1-in. space between the ends, one of which is anchored to the base, at C, the other being attached to the binding post D. Drill a hole through the center of the disk and fasten a lever, taken from a switch, or one made of a piece of sheet brass, that will extend from the center to the outside of the disk, or over the resistance-wire coil. A small handle is attached to the outer end. A connection is made from the center support of the lever to the binding post E.

The connections for the buzzer and rheostat are made on the under side of the base, where grooves are cut to run the wires in, so that they will be below the surface of the wood. In the diagram, the binding post F is connected to the binding post D of the rheostat, which in turn is connected to the screw of the make-and-break point G. The other binding post H is connected to the bracket B supporting the armature spring. The binding post E of the rheostat is connected to the base binding post J. The magnet coils are connected, as shown, from K to L, and from M to B.

The two pieces of carbon, which are used for the hand pieces, are connected with silk-insulated wire. These connections are made to the binding posts F and H. The other two binding posts, J and L, are connected to a battery. The carbons used may be purchased, or taken from an old battery. Two or more dry cells are used for the current. The rheostat controls the amount of current passing through the hand pieces.--Contributed by Gilbert Crossley, Erie, Pa.

Secret Compartment in Ordinary Table Drawer

It is frequently desired to have some handy place for storing valuables where there is but little chance of discovering them. Secret drawers in tables usually require special and expensive changes, but with only a few simple changes on a regular drawer of any ordinary table, a secret compartment can be made which is as secure as can ordinarily be figured on, outside of a steel safe. Having chosen the desired table, a partition should be placed across the entire back part of the drawer, allowing for necessary space in the secret compartment. This partition should resemble the real back of the drawer as closely as it is possible to make it. The compartment must not be too wide, for the resulting small width of the front part of the drawer might then arouse suspicion. On the lower side of the secret compartment a strip of wood, A, should be attached with a screw, as shown in Fig. 1, allowing sufficient looseness so the strip may be turned end for end when necessary. With the strip set as shown, it will strike the front side B of the table when the drawer is pulled out, leaving the secret compartment still hidden. In order to expose this, it will be necessary to turn the strip, as shown in Fig. 2, when the drawer can be pulled out to its full length.

It being necessary that the strip A be as long as the secret compartment is wide, to fully expose this, there may be cases where the drawer is not wide enough to allow the strip A to turn around. In that case the strip can be hinged to the back of the drawer as shown in Fig. 3. When it is hanging down, as shown by the dotted outline, the drawer may be pulled out to its full extent. When it is desired to lock the secret compartment, the hinged strip must be swung up in position, and fastened. An ordinary thumbscrew or eye can be used which, by a turn or two, will either release it or fasten it in place.--Contributed by Paul Durst, Detroit, Mich.

Inflating Handballs

When handballs become "dead," or no longer bounce freely, they may frequently be restored by inflating them with air. This can be done by means of a bulb attached to a hypodermic needle. The needle must be inserted through the soft plug which every inflated ball has, and which can be discovered by pressure. After the ball is inflated and the needle extracted, the soft rubber closes around the fine hole, preventing the escape of the air. If a leak is found, which allows the air to escape too rapidly, a repair can be made with a single-tube tire outfit.--Contributed by A. B. Wegener, Camden. N. J.

A Garden-Bed Scarecrow

A very neat and successful scarecrow for garden beds can be made as follows: A number of corks are procured, and a feather is stuck in each end of them, as shown. These are tied to a string, spacing them from 1 to 2 ft. apart, and the string is hung over the beds. The slightest breeze will keep them fluttering, and no bird will come to rest on the beds.--Contributed by M. T. Canary, Chicago.

Measuring the Length of Wire Wound on a Spool

When winding magnet spools on a lathe, the exact amount of wire used can be easily determined by means of the device shown in the illustration. The large reel from which the wire is obtained is conveniently placed on a loose mandrel, or rod, near the lathe, and in line with the spool which is to be wound. A grooved idler wheel, the exact diameter of which is known, is supported between the spool and wire reel so it may freely revolve; the number of its revolutions should be obtained, automatically, by a revolution counter. When using the device, the wire from the reel is placed once around the idler to insure the necessary grip to prevent it from sliding; then it is led to the spool. The exact diameter of the idler being known and the number of revolutions indicated, the true length of the wire wound on the spools can be easily determined by the following formula: Length of wire on spool in feet equals circumference of idler in feet times number of revolutions of idler.--Contributed by C. Swayne, St. Louis, Mo.

Homemade Lawn Sprinkler

With a short length of old hose, a serviceable lawn sprinkler can be quickly and easily made. One end is provided with a regular coupling for connecting it to the line of good hose. The other end is turned up for several inches, and securely wired to the main part, thereby shutting off any flow through it. Several cuts are made into it, about halfway across and 6 in. apart. If the water is forced in, the only means of escape will be through the slots, which will produce fine sprays, giving as good service as a manufactured sprinkler.--Contributed by A. B. Shaw, N. Dartmouth, Mass.

Homemade Toy Bank

The little bank illustrated is not exactly burglar-proof, but once put together it cannot be opened except by the destruction of one of the units of which it is composed. It requires but little skill to make, and would be a good problem for manual training, as it offers an excellent opportunity for teaching certain rudiments of woodworking by the application method.

In its construction, six pieces of hard wood, of the dimensions shown in the sketch, are required. White wood will do if there is no hard wood at hand. The coin slot is 1/8 in. wide by 1-1/4 in. long, and is cut in only one piece.

No difficulty will be experienced in putting the first five pieces together, but the sixth, or top, piece, shown in the sketch, will not go in, because the bottom edge of the raised side will strike the inside of the piece to the right. By beveling this edge with a chisel from top to bottom between the dadoes, or grooves, it can be forced down quite a distance and sprung in place by placing a block of wood on the high side and striking it a sharp blow with a heavy hammer.--Contributed by J. A. Shelly, Brooklyn, New York.

An Electric Anemometer By Wm. H. Dettman

The construction of this instrument is so simple that any amateur can make one and if accurate calibrations are desired, these can be marked by comparison with a standard anemometer, while both are placed in the wind.

The Indicator

The case of the indicator is built of thin wood--the material of an old cigar box will do--9 in. long, 6 in. wide and 1-1/2 in. deep. If cigar-box material is used, it must first be soaked in warm water to remove the paper. If a cover is to be used on the box, a slot, on an arc of a circle, must be cut through it to show the scale beneath. The arc is determined by the length of the needle from a center over the axis on which the needle swings. When the box is completed, smooth up the outside surface with fine sandpaper and give it a coat of stain.

The core of the magnet is made by winding several layers of bond paper around a pencil of sufficient size to make an inside diameter of slightly over 1/4 in., and a tube 2 in. long. Each layer of the paper is glued to the preceding layer.

Two flanges or disks are attached to the tube to form a spool for the wire. The disks are cut from thin wood, 1-1/4 in. square, and a hole bored through their centers so that each will fit on the tube tightly. One of them is glued to one end of the tube and the other fastened at a point 1/2 in. from the opposite end. The space between the disks is filled with seven layers of No. 22 gauge insulated magnet wire, allowing sufficient ends of the wire to project for connections. The finished coil is located in the box, as shown at A, Fig. 1.

The core for the coil is cut from a piece of 1/4-in. iron rod, 1-1/4 in. long, and a slot is cut in each end, 1/4 in. deep, into which brass strips are inserted and soldered, or otherwise fastened. The strips of brass are 3/16 in. wide, one 1-1/2 in. long and the other 3/4 in. Two 1/16 in. holes are drilled in the end of the long piece, and one 1/16 in. hole in the end of the short piece. The complete core with the brass ends is shown in Fig. 2.

The needle B, Fig. 1, is made of a copper or brass wire, about 6 in. long, and is mounted on an axis at C. The detail of the bearing for the axis is shown in Fig. 3. The axis D is a piece of wood fitted in the U-shaped piece of brass and made to turn on brads as bearings, the center being pierced to receive the end of the needle. After locating the bearing for the axis C, Fig. 1, it is fastened in place so that the upper end or pointer of the needle will travel over the scale. The needle is then attached to the bearing after having been passed through the inner hole of the longer brass strip of the core, and the coil is fitted with the core in the manner shown at D. A light brass coil spring is attached to each end of the core, as shown at E and F, the latter being held with a string, G, whose end is tied to a brad on the outside of the box, for adjustment. A better device could be substituted by attaching the end of the spring F to a nut and using a knurled-head bolt passed through the box side. One of the wires from the coil is attached to a push button, H, to be used when a reading of the instrument is made. The connections for the instrument consist of one binding post and a push button.

The Anemometer

The anemometer resembles a miniature windmill and is mounted on top of a building or support where it is fully exposed to the air currents. It differs from the windmill in that the revolving wheel is replaced by a cupped disk, A, Fig. 4, fitted with a sliding metal shaft, B, which is supported on crosspieces, CC, between the main frame pieces DD. The latter pieces carry a vane at the opposite end. The frame pieces are 1/2 in. thick, 2-1/4 in. wide and 36 in. long, and the crosspieces have the same width and thickness and are 4 in. long.

A variable-resistance coil, E, is made as follows and fastened in the main frame. The core of this coil is a piece of wood, 2 in. square and 4 in. long, and wound with No. 18 gauge single-wound cotton-covered german-silver wire. The winding should begin 1/4 in. from one end of the core and finish 1/4 in. from the other, making the length of the coil 3-1/2 in. The ends of the wire are secured by winding them around the heads of brads driven into the core. A small portion of the insulation is removed from the wire on one side of the coil. This may be done with a piece of emery cloth or sandpaper. A sliding spring contact, F, is attached to the sliding shaft B, the end of which is pressed firmly on the bared portion of the wire coil. One end of a coil spring, which is slipped on the shaft between the pieces CC, is attached to the end crosspiece, and the other end is fastened to the sliding shaft so as to keep the shaft and disk out, and the flange H against the second crosspiece, when there is no air current applied to the disk A. The insulation of the standard upon which the anemometer turns is shown in Fig. 5. The standard J is made of a piece of 1/2-in. pipe, suitably and rigidly attached to the building or support, and the upper end, around which the anemometer revolves to keep in the direction of the air currents, is fitted with a plug of wood to insulate the 1/4-in. brass rod K. A bearing and electric-wire connection plate, L, is made of brass, 1/8 in. thick, 2 in. wide and 4 in. long. The bearing and connection plate M are made in a similar manner. The surface of the holes in these plates, bearing against the pipe J and the brass rod K, make the two connections for the wires from the variable-resistance coil E, Fig. 4, located on the main frame, to the wire connections between the two instruments. These wires should be weather-proof, insulated, attached as shown, and running to and connecting the indicator with the anemometer at NN, Fig. 1.

Two or more dry cells must be connected in the line, and when a reading is desired, the button H, Fig. 1, is pushed, which causes the current to flow through the lines and draw the magnet core D in the coil, in proportion to the magnetic force induced by the amount of current passing through the resistance in the coils on E, Fig. 4, from the contact into which the spring F is brought by the wind pressure on the disk A.

How to Make Stick Shellac

It is often desired to use shellac in solid or stick form, and to get it into this shape by melting and molding requires considerable time. A much quicker method is to place the shellac in a shallow box, spread it out in a thin layer and play the flame from a Bunsen burner upon it until the mass is melted and run together. Allow it to stand a few seconds, then, with moistened fingers, fold it over and over and shape it with the fingers. It is possible to make a stick 8 or 10 in. long and 5/8 in. in diameter in about 5 minutes.--Contributed by J. H. Beeber, Rochester, N. Y.

Substitute for a Hose Reel

Not having the room to spare for the ordinary hose reel, I used as a substitute a piece of wire bent into the shape of a letter S and with its aid coiled the hose in a manner to expel the water and leave it in shape for storing.

The hook A is sprung around the hose about 5 ft. from the connection joint and remains there permanently. The end of the hose with the connection C is then brought around in a circle and forced into the hook B. This forms the start for the coil and the hose is easily rolled up to the nozzle, the water being expelled during the operation.--Contributed by F. H. Aldrich, Toledo, Ohio.

Addressing a Roll of Papers

When addressing rolled-up papers it is difficult to write on the curved surface. The papers also have a tendency to roll away. By placing the roll in the hollow on the front edge of a large book, as shown in the sketch, it will be found easy to write on the wrapper.--Contributed by W. P. Shaw, Toronto, Canada.

Repairing the Bruised Sides of a Motorboat

When the sides of a boat become scored or bruised scrape the parts clean and fill the depressions with wood cement. The wood cement or stick cement, as it is called, can be procured from a paint store. Heat the cement with a blowtorch and apply it to the bruised parts. Use a heated putty knife to smooth the cement and make the surface level. After sandpapering the fills and applying a coat of paint the boat sides will look as good as new. The cement will not chip or fall out.--Contributed by Henry Beck, Bronx, New York.

How to Make an Electric Lamp Flasher

Procure two pieces of metal, one of brass and the other of sheet iron, 5 in. long, 1/2 in. wide, and 1/32 in., or just a little more, in thickness. Bend the brass strip into the form shown in Fig. 1, then place the brass piece on top of the iron and drill the holes A and B indicated in Fig. 2. After the brass piece has been bent, as shown in Fig. 1, it will of course be shorter than the iron strip and the iron strip must be cut off, or a brass strip a little longer than 5 in. can be secured and cut the same length as the iron strip after it is bent. The holes A and B should be 3/32 in. in diameter. The next thing to do will be to wind a heating coil about the brass strip. Wrap a very thin layer of sheet asbestos about the brass strip, and wind on the strip 18 ft. of No. 34 gauge bare superior resistance wire. Use a thread about .006 in. in diameter to separate the various turns. This thread can be removed after the winding is completed and the ends have been fastened. Rivet the iron and brass pieces together with a small brass rivet in the hole A, Fig. 2. After the two pieces are riveted together bend them into the form shown in Fig. 4 and then drill the two 1/8-in. holes C and D, as shown in Fig. 2. Tap the hole B, Fig. 2, to take a small machine screw.

The base is constructed as follows: Procure a piece of slate, 5-3/8 in. long, 1-1/2 in. wide, and 1/2 in. in thickness. Drill the holes indicated in Fig. 3. The four corner holes are for mounting the flasher in its containing case, and should be about 1/8 in. in diameter. The holes E, F, G, and H should be 1/8 in. in diameter and countersunk with a 3/8-in. square-ended drill, on the under side, to a depth of 3/16 or 1/4 in. Cut from some 1/16-in. sheet brass a piece 1-3/8 in. long, and 1/2 in. wide. Drill two 1/8-in. holes in this piece, 7/8 in. apart and equally spaced from the ends. Procure four 1/8-in. brass bolts, two 1/2 in. in length, and two 1 in. in length. Secure four small washers and two additional nuts. Mount the combined iron and brass strip on the slate base, using a long and short bolt as shown in Fig. 4. One terminal of the winding should be placed under the head of the bolt J. Place a washer, K, between the head of the bolt and the wire. The brass strip L can now be mounted in a similar manner, as shown in Fig. 4. Place the other end of the winding under the head of the bolt M.

Obtain a small screw, N, Fig. 4, of such a length that its point will reach the brass strip L when the screw is placed in the hole B, Fig. 2. A lock nut, O, should be provided for this screw so that it will remain in adjustment. The point of the screw and the point on the brass plate where the screw touches should be of platinum, as the brass will not withstand the high temperature of the arc formed when the circuit is broken.

A metal box should now be provided to serve as a containing case and the flasher is complete. This box should be of such design and construction that it will comply with the requirements of the electrical inspection department having jurisdiction over the locality where the flasher is to be used.

The flasher should be connected in series with the lamp, the wires being fastened under the nuts on the bolts P and R, Fig. 4, and the screw N adjusted so that it lacks a small fraction of an inch of making contact with the brass plate when there is no current in the winding. When the switch is turned on there will be a current through the lamp and winding in series. The brass strip will be heated more than the iron and it will expand more, thus forcing the point of the screw N down upon the brass plate, which will result in the winding about the brass strip being shorted and the full voltage will be impressed upon the lamp, and it will burn at normal candlepower. When the coil is shorted there will of course be no current in its winding and the brass strip will cool down, the screw N will finally be drawn away from contact with the brass plate, and the winding again connected in series with the lamp. The lamp will apparently go out when the winding is in series with it, as the total resistance of the lamp and winding combined will not permit sufficient current to pass through the lamp to make its filament glow. The time the lamp is on and off may be varied to a certain extent by adjusting the screw N.

Timing Photograph Prints

An amateur photographer insists that a timing clock in the darkroom is a needless luxury. In order to time printing exposures, which he does with a pendant tungsten light under a reflecting shade, he simply fastens the electric-light cord so that the lamp and shade will act like a pendulum bob which beats the seconds. Of course he makes no effort to be exact, but if the distance between the lamp and the point of suspension of the cord be about 39 or 40 in., the beats will be very nearly seconds. When the light is turned on, it is started swinging, and the operator can thus easily count seconds with sufficient accuracy, and, besides, it readily furnishes a guide for duplicating printing results.

The same principle can be applied to camera exposures, if so desired, by the following plan. Select some suitable place on the under side of the tripod plate, as, for instance, the screw head, and fasten a small string, having a weight attached to it about 39 in. from the point of support. Like the swinging lamp, this device too, will beat seconds. For convenience, one of the tripod legs may be marked to indicate the length of string needed, so that the operator at any time can quickly fasten a string, measure off the right length on the tripod leg, attach a bunch of keys, a knife, or any other convenient weight, even a small stone, and have a second-beating pendulum for time exposures.--Contributed by F. B. Lambert, Chicago.

Supports for Camp-Fire Utensils

The sketch shows how to make a standard or support to hold cooking utensils over a camp fire. The main part or stake is made of a piece of gas pipe, on one end of which is turned an ordinary coupling, Fig. 1. This is used to furnish a strong head when the stake is driven into the ground. The rings and supports for the utensils are made of heavy wire bent into the shape required to hold the respective vessels. The sketch, Fig. 2, shows the manner of shaping the wires.

A Rotary Tuning Coil

The rotary tuner shown in the sketch was designed by a correspondent of Modern Electrics. The circle is cut from 3/4-in. stock, 1 in. wide and well covered with insulating material. It is then wound with No. 24 single cotton-covered copper wire so that the coils will lie flat. All the arms are of 1/4-in. square brass. The supports are smaller in section. Sliders are mounted on the ends of the long arms and are kept in place by setscrews.

The insulation on the wire is removed with a small piece of sandpaper pasted on a block of wood. This should be temporarily fastened to the revolving lever at the point where the contact is wanted, then the lever is turned until the insulation is removed. The wiring diagram shows the location of the tuning coil in the line.

Preparing Sheet Music for Turning

Each page on sheet music having three or more pages should be cut 1/4 in. shorter than the preceding page, as shown by the dotted lines in the sketch. This will enable the player to quickly turn the pages one at a time.--Contributed by Chas. Homewood, Waterloo, Ia.

Toy Parachute Cut-Away for Kite Lines

An interesting pastime while flying kites is to attach large toy parachutes to the lines and have some device to drop them when they are at a great height. In Fig. 1 is shown how the parachute is dropped by the burning of a piece of punk.

Another method is shown in Fig. 2. It is only necessary to send a piece of paper or cardboard along the line and when it strikes the wire coil A (Fig. 2) the part B slides out of the loops C, the end D will then fall and disengage the loop G on the end of the parachute string. The wires E and F are twisted around the kite string.--Contributed by Thos. De Loof, Grand Rapids, Michigan.

How to Make an Electric Furnace

A small electric furnace that will be very serviceable in a laboratory may be made as follows:

First procure a small clay flowerpot, about 4 in. in diameter at the bottom, and also a small clay crucible, about 2 in. in diameter at the bottom and at least 1 in. less in height than the flowerpot, and having as nearly as possible the same slope to its sides as the pot. Now obtain a small quantity of asbestos compound and pack it around the small crucible inside the flowerpot. Make sure the crucible is in the exact center of the flowerpot and that their tops are even with each other. Assuming that ordinary electric-light carbons are to be used, which are about 1/2 in. in diameter, drill two 5/8-in. holes, exactly opposite each other, through the walls of the flowerpot and asbestos compound so that they enter the crucible about 3/4 in. above its bottom on the inside. A suitable lid for the furnace may be made from 1/4-in. sheet asbestos and should be large enough to cover the top of the flowerpot.

The feeds and supports for the carbon electrodes are constructed as follows: Procure two pieces of 1/8-in. brass, 1 in. wide and 9 in. long. Cut a 1/8-in. groove lengthwise in the center of these pieces to within 1-1/2 in. of each end, as shown in Fig. 1. Drill four 1/8-in. holes, AA, in each piece, a 3/8-in. hole, B, in one end and a 3/16-in. hole, C, in the other end. Now bend the ends up at right angles to the remainder of the piece along the dotted lines shown at D and E. Next obtain two 3/8-in. rods, 10-3/16 in. long. Turn one end of each down to a 3/16-in. diameter for a distance of 3/8 in. From that point thread the same end of the rods for a distance of 6 in. Drill a 1/16-in. hole in each end of the rods a little less than 1/4 in. from the ends. The dimensions of the rods are given in Fig. 2. Two small rubber or wooden handles, similar to the one shown in Fig. 3, should now be made and fastened to the large ends of the rods by means of 1/16-in. steel pins. Obtain two pieces of brass of approximately the following dimensions: 1 in. by 1 in. by 3 in. Drill four holes in each of these pieces as shown in Fig. 4. The hole H should be just large enough to allow the carbon to enter, or about 1/2 in. in diameter. The hole G should be tapped to take a 1/4-in. machine screw, the hole F should be threaded so that the threaded rods will enter, and a small binding post should be mounted on a lug fastened in the hole J. Cut away one end of this piece as shown in Fig. 4 until it is a little less than 1/8 in. in thickness, or so it will enter the grooves cut in the brass strips.

The parts of the furnace are now ready to assemble, which may be done as follows: Procure a piece of well seasoned board, hard wood if possible, about 1 in. thick, 8 in. wide and perhaps 20 in. long. Cover one side of this board and the edges with some 1/8-in. sheet asbestos. Now place the flowerpot in the exact center and then mount the grooved brass strips one on either side of it with the longest dimension parallel to the longest dimension of the board and the inside end about 1 in. from the side of the pot. The end with the 3/16-in. holes should be next to the pot. Assemble the parts of the carbon feeds and then cut out some circular disks of asbestos to place under the flowerpot so as to raise it to such a position that the holes in its sides will be on a line with the carbon rods. Three long screws should now be placed in the board, forming the base, in such a position as to hold the flowerpot always in place. This completes the furnace proper, which is shown in Fig. 5.

The furnace can now be put into operation provided there is a suitable current rheostat to connect in series with the carbon arc to prevent an excessive current being taken from the line. If such a rheostat is not available, a serviceable one may be made as follows:

Obtain two pieces of 1/16-in. sheet iron, 6 by 6 in., that are to form the end plates. Cut off the corners of one piece so as to form an octagon and drill a number of 1/8-in. and 1/4-in. holes in it, as shown in Fig. 6. Bend the corners of the other piece down along the dotted lines marked L, Fig. 7, and then make a second bend in each corner along the dotted lines K, so that the outermost portion of the corner is parallel to the main portion of the piece. Drill a number of 1/8-in. holes in this piece as indicated. A 3-in. opening should be cut in the center of this piece to give access to the interior of the completed rheostat. Now obtain eight 3/8-in. iron rods, 10 in. long. Drill and tap each end of these rods to accommodate a 1/8-in. machine screw. Wrap several layers of thin sheet asbestos around each rod and tie it in place with some thread. These rods should now be fastened between the end plates by means of a number of iron machine screws. Mount four back-connected binding posts on the plate shown in Fig. 6, making sure they are insulated from the plate by means of suitable bushings and washers.

Procure a small quantity of No. 14 gauge iron wire. Fasten one end of the wire under the head of the screw holding one of the binding posts in place and then wind it around the rods about 20 times, making the distance between the turns equal to the diameter of the wire. After winding on the 20 turns, attach a short piece of wire to the main wire and fasten the free end of the short piece to one of the other binding posts. Wind on 20 more turns, and make another connection to the third binding post, then complete the winding and attach the end to the remaining binding post. Different amounts of this resistance can now be connected in series with the arc by changing the connections from one binding post to another. The rheostat may be located on a bracket fastened to the wall, but care must be taken not to place it in such a position that it will come into contact with inflammable material. As an extra precaution, the circuit should be properly fused.

Cleaning Brass Articles

Embossed or undercut brass work may be easily cleaned by boiling the pieces in a strong solution of caustic soda or lye, and then immersing them in a mixture of hydrochloric acid, 6 parts; water, 2 parts, and nitric acid, 1 part, until they become covered with a dark deposit. Take them from the solution and remove the black substance with a fine scratch brush. After cleaned in this manner, rinse in hot water and dry in hot sawdust.

A fine orange-yellow tinge may be given to the brass by substituting an equivalent weight of powdered alum for the nitric acid in the solution.--Contributed by Mrs. Richard F. Pohle, E. Lynn, Mass.

A Whetting Block

A handy tool gauge for sharpening the various tools about the household is made of a block of wood with the sides of one end cut sloping in different degrees so that each will serve to secure the proper slant of the cutting edge on a certain tool.

The block of wood with the corners cut is shown in Fig. 1, and the manner of whetting a chisel is shown in Fig. 2.--Contributed by Will Parker, Wibaux, Mont.

* * * * *

A cardboard cut the same size as a page and fastened with paper clips in the center of a magazine will prevent the pages from folding over when the magazine is placed in a bookcase.

Submarine Photographs

A photographer at a seashore resort, wishing to increase his sales of souvenir postal cards, rigged up a device for producing negatives to make "submarine" pictures. The device consisted of an aquarium, about 40 in. long, 18 in. high and 6 in. wide. The aquarium was designed to stand on edge or the narrow way, and was equipped with rocks, living sea moss, kelp, and some fish, and the bottom was covered with sand and shells.

A canvas was hung back of the aquarium and the camera set in front at such a distance as to make a negative of only the water and the prepared sea bottom. Very fine views that will give the appearance of being made at the bottom of the sea can be produced.

Mending Paper-Pulp Utensils

Pails, washtubs, and other receptacles made of paper pulp, when cut and worn, may be easily mended with adhesive tape. After this is applied to the place to be mended, give the mended part a coating of paint, and when the paint has dried, the surface is given another coat to match the color of the article mended. Leaks may be entirely stopped in this way at a very reasonable cost.--Contributed by Katharine D. Morse, Syracuse, N. Y.

A Homemade Mailing Tube

A photograph or manuscript may be sent through the mail unmounted without the danger of being broken by placing it in a tube made as follows: For an 8 by 10-in. photograph procure a piece of cardboard 6 by 10 in., plain mounting board preferred, and cut halfway through the card in three places as shown by the dotted lines in Fig. 1. Then fold it in a triangular shape as shown in Fig. 2. It is easy to make such a tube to fit any photograph or manuscript to be mailed.--Contributed by A. H. Schaefer, Buffalo, N. Y.

Cutter for Lace Leather

Lace leather may be easily cut with an ordinary pocket knife having a U-shaped block fitted on the edge of the blade. The width of the opening should be exactly the same as the thickness of the leather and the width of the lace is determined by the distance between the blade and the depth of the notch. Several places can be provided for the blade to cut different widths of lacing.--Contributed by A. K. Runkle, Kinsman, O.

Refinishing Chairs

When refinishing chairs, a good way to get at the bottom part is to turn the chair upside down and place its seat on the seat of another chair. The legs and rungs can thus be easily cleaned and varnished.--Contributed by A. Mandeville, Ware, Mass.

An Electric Gas Lighter

A very simple and inexpensive electric gas-lighting device is shown in the accompanying illustration. The gas is ignited by means of an electric spark which is produced between the two parts A and B of an electric circuit. This circuit is composed of a source of electrical energy, such as a number of dry cells, a kick coil, the connecting leads, and a special operating switch for opening and closing the circuit to produce the spark. The circuit is normally open, but as the lever controlling the gas valve is moved from one position to the other, by pulling the chains, the lever C is caused to move through a certain arc. Now, as this lever C moves, its upper end passes the projecting point B, which is attached to the upper portion of the burner, and the electric circuit will be completed and broken. Just as the point A leaves contact with the point B an arc will be produced. This arc is greatly intensified by the kick coil, which acts as a sort of reservoir in which energy is stored while the circuit is closed, and upon opening the circuit this stored energy is given out by the kick coil and increases the size of the arc.

The points A and B should both be made of platinum, as other metals will not withstand the extremely high temperature of the arc. Pieces of platinum that will serve very nicely for the purpose may be obtained from an old incandescent lamp. The piece B is mounted on a brass collar, D, by means of a small screw, E. The brass collar D is held in place by the screw F, which draws the two ends together. This collar must be insulated from the stem or fixture by some thin sheets of mica. The upper end of the piece of platinum B should be just high enough to come within the lower edge of the gas flame.

Now mount an arm, C, on the valve stem so that it stands in a vertical position when the lever to which the chains are attached is in a horizontal position. Bend this arm into the form shown in the figure and cut its upper end off so that it is about 1/2 in. below the outwardly projecting end of the piece of platinum B. Drill a small hole in the upper end of C, and insert a piece of platinum and run some solder around it.

Then the complete burner and valve are mounted on the gas fixture, and from the collar D an insulated wire is run to the point where the battery and kick coil are to be located. The gas fixture itself is to form one side of the electric circuit, and one terminal of the battery should be connected to the gas pipe as shown in the figure.

A kick coil may be made as follows: Procure a small quantity of rather small soft-iron wire and cut a sufficient number of 8-in. lengths to make a bundle about 7/8 in. in diameter. From some good writing paper make a tube, 8 in. long and 7/8 in. in outside diameter. Use at least six layers of paper and glue the various layers together in forming this paper tube. After the tube has dried thoroughly, fill it with the pieces of iron wire until it is perfectly hard. Cut from some 1/2-in. hard wood, two pieces, 3 in. square, and drill a 7/8-in. hole in the center of each of these to a depth of 3/8 in. Now glue these pieces to the completed core and the winding can begin as soon as the glue is dry. Wind on this spool six layers of double cotton-covered No. 18 gauge wire, insulating the various layers from each other with several thicknesses of good writing paper. This coil is then mounted on a wooden base and suitable terminals provided.

At least four dry cells will be required to give satisfactory results. Bear in mind that the gas must be escaping from the burner when the arc is formed. The adjustment of the arm A, as given above, may result in the gas valve being closed when the arc is formed, and the device will then fail to operate. If this is the case, the arm C should be loosened and moved back so that the circuit is broken at a later time while the valve is being moved from the "off" to "on" position. The circuit should be closed for some little time before it is opened so that some energy may be stored in the kick coil. If the wire A is made long enough to project a short distance above B, it will result in the circuit being closed for a longer time than it would if they just touched.

Stretching Tight-Fitting Shoes

A tight-fitting shoe can be stretched by filling it tightly with oats dampened in water and packing some old paper in the top. The grain will quickly swell and, as the leather will get softened by the dampness, the shoe will be rapidly stretched. Allow time for the oats to dry out before removing them.--Contributed by Fred L. King, Islip, New York.

Pad for a Percolator

To prevent heating the bowl of a percolator and burning the handle, as often happens when it is placed on a stove, use an ordinary asbestos pad with a hole cut in the center as shown, just large enough to admit the foot of the percolator.--Contributed by Mrs. G. W. Coplin, Bay City, Mich.

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If a motorcycle engine is raced while on the stand, the cylinder will heat, often with the result that it is ruined.

Compass Time Chart

A very instructive little instrument can be easily made for telling the time of any location on the globe. Its construction is extremely simple. Draw a circle, about 1-1/2 in. in diameter, on a piece of paper and then draw a larger circle, about 4 in. in diameter, around the first one. Divide the circles into 36 equal parts and draw lines from one circle to the other like the spokes in a wheel. These divisions will be 10 deg., or 40 minutes of time, apart. They should be numbered around the outside, commencing at a point marked 0 and marking the numbers by tens each way until they meet at 180 deg.

Using a map of the eastern and western hemispheres, write the names of the different cities on the globe in their respective degrees of longitude. The center, or inside, of the smaller circle is divided into 24 divisions representing the hours of the day and night, and these are marked from 1 to 12, the left side being forenoon, and the right, afternoon. The noon mark must be set on the line nearest to the location in which the instrument is to be used. For instance, if the instrument is to be used in Chicago, it is set as shown in the sketch.

The disk is mounted on a thin piece of board and a pin is driven through the center from the back side so as to make a projecting point on the upper side on which to place the magnetized needle of a compass. The needle may be taken from any cheap compass.

All that is necessary to do, to tell what time it is in any other city or country, is to turn the instrument so that the name of that place points toward the sun, when the north end of the compass needle will point on the disk to the time it is in that city or locality.--Contributed by Henry J. Marion, Pontiac, Mich.

Reversing Switch for Small Motors

A reversing switch made as follows will be found very serviceable in reversing the direction of the rotation of small motors, changing the polarity of electromagnets, etc.

A diagram of the connections to the switch and on the switch base is given in the sketch, and in this particular case the switch is shown connected to a small toy motor. The field of the motor is represented by A, the armature by B; and C, D, E, and F are four binding posts mounted on the base of the switch; G, H, and I are three contacts; J and K are terminals of the switch blades, and L a single-pole switch. The two blades of the reversing switch have their lower ends fastened to the terminals J and K, and their upper ends, which are indicated by arrow heads, may be moved over the contacts G, H, and I. For the position of the reversing switch shown by the full lines, J is connected to G and K to H. When the switch is thrown to the right-hand position, as shown by the dotted lines, J is connected to H and K to I. It is obvious that the direction of the current through the armature B will be reversed when the reversing switch is thrown from one position to the other. The direction in which the armature rotates will change, due to the reversal in direction of the current through it. The same results could be obtained by reversing the current in the field winding A. But it must always be borne in mind that in order to reverse the direction of rotation, the current must be reversed in the armature only or in the field only, not in both.

The above switch may be constructed as follows: First, procure a piece of well-seasoned hard wood, say maple, 1/2 in. thick, 2-1/2 in. wide and 4 in. long. Round off the corners and the edges of this piece on one side and drill the holes indicated in the sketch. The four corner holes should be of such a size as to accommodate the screws used in mounting four small back-connected binding posts. The remaining holes should be 1/8 in. All these holes should be countersunk with a 3/8-in. bit to a depth of 1/4 in. on the under side.

Cut from some 1/16-in. sheet brass two pieces, 2-3/4 in. long, 1/2 in. wide at one end and 1/4 in. at the other, and round their ends. Drill a 1/8-in. hole through the larger end of each of these pieces, 1/4 in. from the end, and also a hole through each, 1-1/4 in. from the narrow end. The last two holes should be threaded for 1/8-in. machine screws. Obtain five 1/8-in. brass bolts, 1/2 in. long. File the heads of three of these bolts down to a thickness of approximately 1/16 in. and mount them in the holes G, H and I. Before mounting anything on the base the grooves indicated by the heavy dotted lines should be cut in the under side so that the various points may be properly connected by conductors placed in the grooves. Now mount the two pieces of sheet brass upon the base by means of the remaining two bolts, which should pass through the holes J and K. A 1/16-in. washer should be placed between the pieces of brass and the wooden base.

Procure a piece of 1/8-in. fiber, 1-1/4 in. long and 3/8 in. broad. Drill two 1/8-in. holes in this piece, one in each end, so that they are 1 in. apart. Drill a third 1/8-in. hole in the center and fasten a small handle to the piece of fiber. Now mount this piece upon the two pieces of brass that form the blades of the switch by means of two small 1/8-in. brass machine screws.

Two small brads should be driven into the wooden base so as to prevent the possibility of the switch blades moving beyond their proper position. Two pieces of 1/16-in. fiber should be placed between the heads of the screws G and H, and H and I, to prevent the ends of the switch blades from dropping down on the wooden base.

Adjustable Rod for Potted Plants

Procure a brass sash-curtain rod of the telescoping kind and stick the solid part into the soil close to the plant and tie it to the rod. As the plant grows move the tubular part of the rod upward to correspond with the height of the plant. This makes a good support and is not so unsightly as a stick.--Contributed by Gertrude M. Bender, Utica, N. Y.

Wrench for Different-Size Nuts

A very handy wrench can be made from a piece of square bar, shaped as shown and fitted with a handle. The joint at A may be halved and riveted or a weld made as desired. The size of the bar and the space between the parts will depend on the size of nuts to be turned.

A Simple Sextant

A sextant for measuring the latitude of any place can be easily constructed as follows: While a board, 1 in. thick, 6 in. wide, and 12 in. long is about right for the instrument, any dimensions can be used, providing the line AB is at perfect right angles to the level of the sights C and D. The sights are better to use, although the upper edge of the board, if it is perfectly straight, will do as well. If it is desired to use sights, a slight groove is cut in the upper edge; a V-shaped piece, cut from tin, is fastened at one end, and a small pointed nail is driven in at the other. In doing this, be sure to level the bottom of the V-notch and nail point so that in drawing the line AB it will be at perfect right angles to a line between the sights. A tack is driven into the side of the board at the upper edge, a line fastened to it and a weight tied to the lower end which should swing below the lower edge of the board.

The instrument is placed in such a manner that the North Star is sighted, as shown, and the point on the lower edge of the board is marked where the line E comes to rest. A line is then drawn from A to the point marked and the angle F is measured with a protractor. The number of degrees in this angle will be approximately equal to the number of degrees in the latitude of that place.

The North Star is easily located by reason of its position relative to the Great Dipper, as shown by the diagram.--Contributed by Carlos Harrison, Anderson, Ind.

How to Make a Taper Ferrule

Having occasion to make a taper ferrule of irregular form, a pattern from which to cut the material was made as follows: A mandrel of the desired shape was made, a piece of writing paper, soaked in water, wrapped around the mandrel, and a piece of twine wound over it, coil after coil like the thread on a spool. This was allowed to dry thoroughly, using a little heat. The string was then removed and a longitudinal cut made in the paper while on the mandrel. When opened this paper formed the pattern.

A piece of metal was cut from the pattern and the edges were brought together and brazed with spelter. The point of the mandrel was driven through a piece of block tin, about 1/2 in. thick. The mandrel was then removed, the ferrule was placed on it, and both then started in the hole made in the tin and driven through it. As the mandrel with the ferrule passed through the tin, the metal was shaped exactly to the mandrel. It is best to oil the hole in the tin slightly. Tin is preferable as it is harder.--Contributed by James H. Beebee, Rochester, N. Y.

How to Make a Continuously Ringing Bell

The bell shown in the accompanying diagram is known as the continuously ringing type, and has quite a field of usefulness in connection with burglar alarms, door-bell signals, telephone signals, etc. The operation of the bell proper is identical with that of the ordinary vibrating bell and, in addition, there is a circuit controlled by the armature of the bell, which is normally open, but becomes closed as soon as the armature is drawn over. The closing of this circuit by the operation of the armature amounts to keeping the push button in the bell circuit depressed, and the bell will continue to ring until the latch A is restored by pulling the cord B.

Any ordinary vibrating bell may be converted into a continuously ringing bell as follows: In the armature, C, mount a short metal pin, D, and round off its under side slightly. A latch, A, should now be constructed similar to the one shown in the sketch and mounted in such a position that its left end will rest on the outer end of the pin D when the armature, C, of the bell is in its extreme outer position. The length of the latch should be such that its left end will drop off the end of the pin D, due to the action of the spring E, when the armature C is drawn over by the electromagnets F, thus allowing it to come into contact with a spring G, which is electrically connected to the terminal of the bell marked H. The latch A is connected to one side of the line, as shown in the sketch, so as to include the bell winding and battery in a local circuit that is formed by the latch coming in contact with the spring G. The end of the latch should not interfere with the free operation of the armature when it is resting on the spring G. A cord, B, attached to the outer end of the latch, is used in restoring it, and at the same time stopping the bell from ringing. The tension in the spring E should be so adjusted that the operation of the latch is sure and firm, yet not too stiff.

A Mission-Style Inkstand

Having a couple of good-sized ink bottles of the ordinary type lying around, I fashioned a mission-style stand for them out of a piece of yellow pine, 2 in. wide and 3 in. long, set on another piece of pine large enough to project all around on all four sides of the block, for a base. The wells were cut out with a wood chisel, and the parts fastened together with screws. The supports were four brass-head or upholsterer's tacks. The finish was flat black.--Contributed by James M. Kane, Doylestown, Pa.

Raising Dents in Wood

The imprint of a hammer on finely finished wood caused by a glancing blow, or otherwise, may be removed in the following manner: Pour enough wood alcohol on the dented spot to cover it, then light the alcohol and allow it to burn out. The heat will expand the wood and raise it enough so that the spot can be planed and smoothed in the usual manner.--Contributed by W. F. Elwell, Waltham, Massachusetts.

Carrying Two Pails in One Hand

When it is necessary to carry two small filled pails in one hand and a package in the other it will be found a very difficult job, if the contents are liquid. Procure a stick of sufficient size to carry the weight of the pails and cut a small notch in each end to admit the bail. Place a pail on each end of the stick and take hold in the center, or, if the pails are not equally filled, a little to one side of the center.

Preserving Paint in Open Cans

To keep paint from drying out in an open can it is necessary to exclude the air from the oil. This can be done by procuring an air-tight paper sack, which is tested by blowing into it. Set the can into the sack and tie it tightly with a cord. Mixed paint will be kept in a working state in this manner.

Jelly-Straining Stand

Procure a board, 7/8 in. thick and 18 in. square, and cut a hole, about 1 ft. diameter, in the center. Fasten posts, 4 ft. long, to each corner. Screw hooks are located around the edge of the hole to catch into the cloth used for holding the fruit. The stand is high enough to be convenient and admit a vessel beneath to catch the juice.

Renewing Dry Batteries

It is a well-known fact that dry cells commence to deteriorate from the time they are manufactured, and it is a matter of considerable uncertainty in purchasing cells to know whether they will continue to be efficient for their supposed natural life under the existing conditions of service, or for only a small part of this period. When the voltage of a dry cell falls below a certain value it is usually discarded and replaced by a new one, which often means quite an expense. The following simple suggestion will enable one to renew the prematurely exhausted cell with very little trouble and slight expense, so that its period of usefulness will be extended for a length of time, at least equal to that for which it could be used if put into service immediately after its manufacture.

The procedure in renewing the cell is as follows: A casing is placed outside of the zinc-containing case, having inside dimensions a little greater than the zinc cup. The space between the zinc cup and case is filled with a dry electrolyte, which, upon the addition of moisture, sets up a chemical action with the exterior surface of the zinc, and the latter having been perforated, causes electrical action to be again produced.

The casing, or cup, to be used outside the zinc cup should be made of a waterproof material. The electrolyte instead of being placed between this cup and the zinc in a powdered form, as might be expected, should be held by several layers of blotting paper, formed into a cylinder of the proper diameter to fit snugly on the outside of the zinc cup. This porous cup should be impregnated with a solution containing the following materials in the approximate amounts given: Muriate of ammonia, 10 parts; bichromate of potash, 4 parts, and chloride of sodium, 4 parts. After the porous cup has thoroughly soaked in the above solution it should be dried by passing a roller over its external surface when it is mounted on a wooden cylinder of proper diameter. The moisture-proof cup may be formed outside the porous cup by covering the latter with several coats of waterproofing paste and winding on several thicknesses of common manila paper, each layer of paper being treated with the paste. A disk of cardboard, properly treated, should be placed in the end of the cylinder to form the bottom, and the edge of the manila paper folded in over it and pasted in place.

The pasteboard covering surrounding the zinc cup of the cell should be removed and the surface of the zinc thoroughly cleaned. The coal tar in the top of the zinc cup should be removed by tapping around the edge with a hammer, and a large number of small holes should be made in the walls of the cup with a sharp instrument. Then put the cell within the porous cup and fill the top with clear water, preferably rain water. A chemical reaction will immediately take place between the outer surface of the zinc and the chemicals contained in the material forming the porous cup, and the terminal voltage of the cell will be practically the same as it was when the cell was new. The water, of course, must be replenished from time to time on account of evaporation, and the useful life of the cell can be prolonged for a considerable time. A part cross section of a cell treated as described above is shown in the accompanying sketch.

Workbench Equipment for a Table Top

The average home mechanic with a few tools seldom has a place to work and is usually without a workbench. As this was my case, I constructed a bench equipment that I could easily clamp to the kitchen or other table and thus have the necessary tools at hand for work. A plank, 2 in. thick, 10 in. wide and 18 in. long, was planed and smoothed up on all sides, and a vise and a bench pin were fastened on one edge.

To the under side of the same edge two blocks were securely fastened, as shown, and to these blocks two other pieces were fastened with hinges. With a bolt, running through from the top, and a thumb nut used underneath, these pieces are used as clamps for holding the bench to the table top. The top can be removed and set away in a closet when not in use.--Contributed by Wm. H. Hathaway, Nutley, N. J.

A Nonsticking Drawer Guide

The guide shown is nonbinding and has been found thoroughly practical after several years' use on furniture. The guide A consists of a piece of wood, about 1-1/8 in. square, with a concave cut in its upper edge, the width being about 3/4 in. and the depth such as not to cut through the extending end projecting over the crossbar B. The drawer sides have a half-round edge on the bottom edge to run in the groove in the guide. The difference in width between the groove in the guide and the rounding edge on the drawer side causes the drawer always to ride snugly without binding as the wood expands or contracts with changes in the weather.--Contributed by Herman Hermann, Portland, Ind.

A Milk Stool

The stool is made of three pieces of board and a piece of round, or stake, iron. The appearance and manner of construction are clearly shown in the illustration. The seat board is sawed out to fit the circumference of the bucket to be used, and the iron is also bent to this curve and fastened to the board as shown. The little shelf on the front support holds the bucket at the right height, and keeps it clean and out of the way of the cow's foot while milking.

Sounder for Wireless-Telegraph Messages

The owner of an amateur wireless outfit often has reason to regret that he cannot let some of his friends listen to a message at the same time as he himself. The magnifier described in the following permits all those present in the room to hear the message, provided, of course, they are able to interpret the Morse alphabet by sound.

A very simple means, making the message audible at a distance of about 10 ft., is to attach a phonograph horn, or a horn of cardboard or metal, to the telephone receiver, but a much better arrangement can be made as shown in the diagram, in which A represents the antenna or aerial; B, the detector, and C, the receiver. Procure a small microphone, D, placing its mouthpiece closely against the receiver--for the sake of clearness the two are separated in the diagram--and connect the former with a battery, F, of two or three dry cells, in series with the microphone of an ordinary telephone transmitter provided with a large horn. The effect obtained by this simple means will be surprising.

Joint for Mission Furniture

The mortise for this joint is made in the usual manner, the only requirements being that the mortise is run through the piece, and the tenon is cut 1/8 in. shorter than the depth of the mortise or the width of the piece it is entering. The end of the tenon and the mortise is then covered with a piece of metal, fastened with screws as shown. The metal can be of any desired material and beveled on the edges. This makes a very good knock-down joint for mission furniture.--Contributed by H. R. Allen, Cheyenne, Wyoming.

A Towel Roller

A substantial, convenient and nonrusting towel roller can be made from 8 or 9 of the familiar wood handles on bundle carriers and a length of brass curtain rod. The bracket ends can be shaped from any piece of wood of suitable dimensions. The rollers and ends can be finished as desired.--Contributed by F. E. S., E. Lynn, Mass.

An Electric Shaving Mug

The general use of electricity in the home has opened up a new field in the way of heating and cooking utensils. While these utensils are sold by electric-supply houses, some of them can be easily made at home and answer the purpose just as nicely. One of these is the electric shaving mug.

A mug that will stand heat is the first thing required, and an aluminum cup of standard shape and design, which can be bought in almost every town, will do perfectly well. These cups are spun from a flat sheet and have no seams to open and leak, and it is necessary that no holes be drilled in the cup as it is impossible to make such a hole watertight. The heating element must be fastened to the mug with a clamp. The clamp will also allow the heating coil to be removed for repairs without injury to the mug. The bottoms of these mugs have a flange which makes a recessed part and in this the heating element is placed.

The legs of the mug are made of sheet brass as shown in Fig. 1, one of the three having an enlargement near its center with a hole for an insulating button (Fig. 2), of "transite" or some other material, to hold the supply cord in place.

The clamp for holding the heating coil in place is shown in Fig. 3. This clamp has a screw in the center to tighten it in place. The legs and clamp may be nickelplated if desired.

The heating coil is shown in Fig. 4 which is a coil of flat "Nichrome" wire, or ribbon as it is called, 12 ft. long, 1/16 in. wide and 3/1000 in. thick. This is equal in cross section to a No. 26 gauge wire. To wind this coil, procure a block of wood, 7/8 in. thick and about 4 in. square, with a 1/2-in. hole in the center for an axis or pivot. Clamp a 1/2-in. rod in a vise so that the block can be rotated about it. Begin at the center and fasten one end of the ribbon to the block, leaving about 2 in. projecting for a connection, then proceed to wind the ribbon in a spiral coil, separating each turn from the preceding one with a strand of asbestos cord. A small section of the coil is shown in Fig. 5, in which A, or the light part, represents the asbestos insulation, and B, or the black lines, the heating element. The insulation may be obtained by untwisting some 1/8-in. round asbestos packing and using one of the strands. This cord insulates each turn of the ribbon from the other and the current must travel through the whole coil without jumping across from one turn to the other. The whole coil must be closely wound to get it into the limited space at the bottom of the mug.

Before taking the coil from the block, rub into its surface a little asbestos retort cement, or a cement composed of a mixture of silicate of soda and silica, or glass sand. This mixture, when dry, will tend to hold the coil together and the current may be passed through the coil to test it as well as to bake it in its coiled shape.

The support for the heating coil is made of a piece of 5/16-in. asbestos wood or transite. Cut it to fit into the recessed bottom of the mug, then with a chisel remove the material in the top to form a depression 1/16 in. deep to receive the coil with its top flush. The leads of the coil are run through the disk. The surface of the coil is then plastered evenly with retort cement. The legs are fastened to a second piece of insulating material with round-head brass machine screws, 1/2 in. long, with nuts. The heads of these screws are shown in Fig. 6, the nuts being above the brass and between the two insulating pieces.

The ends of the heating ribbon are brought through the lower insulating disk and attached to binding posts as shown. The leads may be covered with tape to prevent any short circuit.

The mug uses 3-1/2 amperes at 110 volts, either direct or alternating current, and it will cost about 3 cents an hour to operate it. Care should be taken to use a separable attachment for connecting, as an ordinary lamp socket may be burned out by turning off the current, it being adapted only to a small capacity.

In assembling the parts, several pieces of mica should be placed between the coil and the metal of the mug to insulate the coil from the mug.

A Handbag Lock

The pickpocket finds it easy to unsnap a handbag and remove some of the contents, especially in crowded places. To make it less easy for the pickpocket, I fixed my mother's handbag as shown in the sketch. I used a chain which had served its day holding a small coin purse--any small chain will do--by passing it through the links that hold the handle and winding it once or twice around the snap fasteners to hold them securely closed.

The chain may be either shortened enough to make it convenient to hold with the handle of the handbag, or may be left long and used over the shoulder under the coat, thus making it possible to have both hands free for shopping while the handbag hangs by the side. This leaves a person free from the worry of taking care that the bag is not laid down somewhere and lost. The bag may be easily opened by unwinding the chain after loosening it by raising the bag slightly.--Contributed by Wm. Waterhouse, Aurora, Ill.

An Emery-Cloth Holder

Emery cloth in sheets is very easily spoiled around a workbench. Oil or other fluids used on work are apt to drop on it and when wet for a short time the abrasive is useless. The illustration shows a tin holder, A, that can be placed on the under side of the bench where space is not required for drawer room.

The portion cut out of the bottom of the holder B is to enable the workman to easily grasp the sheets of emery cloth. As the holder is on the under side of the bench, there is little danger of any liquid or other substance spoiling the sheets. The sheets are also within easy reach.--Contributed by F. W. Bently, Huron, S. D.

The Operation of the Compass

After trying to tell a few small boys what a compass is, they wanted a practical illustration--something they could see. Not having a compass or knowing where to locate one handily, I used a piece of cork with needles and a needle for a pivot and found it very satisfactory. The method used is shown in the sketch.

It is best not to magnetize both needles unless care is exercised in maintaining pole relationship, or they will oppose each other and not point to the north. The extreme ends or the heads of the needles must be opposites, the head of one negative and the head of the other positive.

If a good compass is brought carelessly in contact with a magnet, the poles may become reversed and the north end will no longer point to the north but to the south until the current has been reversed again by bringing the opposite pole of the magnet in contact with the compass.--Contributed by W. H. Albright, Bellevue, O.

Thawing Out Frozen Pipes

When the water pipes connecting a range boiler become frozen, get a plumber and avoid an explosion of the water back. If, however, the frozen pipe is a cold-water pipe in no way connected with the hot-water boiler, it can be thawed out as follows:

Procure some grain alcohol--not denatured or wood alcohol--and after turning the spigot upward or upside down, as shown, open it and pour in the alcohol. When the water begins to flow turn it to its proper position.--Contributed by James M. Kane, Doylestown, Pa.

A Wire Clothespin

The pin is made of galvanized wire, A, 8 or 10 in. long, wound spirally, B, on a round surface, such as a broom handle, to make the holding part. The ends are fastened together as shown. The space between the spiral turns makes the cloth-holding part.--Contributed by Wesley H. Freeman, Palestine, Tex.

Vent for Pouring Heavy Liquids

A tube placed in a jug or bottle as shown in the sketch will assist greatly in removing molasses or heavy liquids. The tube can be placed in the receptacle without getting the liquid inside by holding a finger over the outer end. The air can easily enter without disturbing the flow of the liquid.--Contributed by Homer Payear, Owensboro, Ky.

A Hat Hanger

Procure a piece of 1/8-in. wire, about 3 ft. long, bend it into the shape shown in the sketch, and sharpen the projecting end. Drive this into the wall above a coat hanger. This provides a better hat hanger than the ordinary hook.--Contributed by John D. Watt, Roxbury, Mass.

Repairing a Broken Tenon on a Chair Post

Instead of cutting off the four posts to make new tenons where one tenon was broken I used a metal piece made from a short length of bicycle tubing, as shown. The tube was slotted two ways to make four parts which were turned out and flattened. The remaining end of the tube was slipped over the broken post and the four parts were fastened with screws to the under side of the chair seat.--Contributed by Chas. H. Roberts, Calumet, Mich.

Substitute for an Iron-Holder Knob

The wood knob on the holder for my irons became charred from the heat and finally broke away from the pin. The pin would get so hot in continued use that it could not be moved without burning my fingers. I remedied the difficulty by attaching a short string to the handle and the pin. A pull on the string with the forefinger readily released the iron. I have found this better than the knob, as it is handier to use.--Contributed by Mrs. H. C. Dixon, Johnstown, Pa.

An Egg-Frying Pan

The frying of eggs in an ordinary frying pan is accompanied with some difficulty in removing them when they are cooked without breaking the yolk. Then, sometimes, the pan is too hot and the egg sticks to the pan and the top remains uncooked. A much better way is to shape a piece of sheet metal or tin as shown in the sketch to place the egg in and use it in the ordinary pan. It will not burn the egg, and the egg can be lifted out of the pan and easily slipped on a plate or toast when it is cooked.--Contributed by W. A. Jaquythe, San Diego, Cal.

A Sander Mandrel for the Lathe

A cylindrical sander for use in the lathe can be easily made of two pieces of wood, turned to a diameter that will take the stock size of sandpaper, and clamped together with pinch dogs at the ends. One edge of the sandpaper is clamped between the pieces and then it is wrapped around the wood, the opposite edge being glued to the starting edge, as shown at A. The dimensions given are for a 9 by 12-in. sheet of sandpaper. The sander is easily placed in the lathe centers when needed, and the sandpaper may be replaced at any time.--Contributed by James T. Gaffney, Chicago.

How to Construct a Simple Galvanometer

A galvanometer is an instrument used to detect the presence of an electrical current in a circuit or to measure the value of the current in amperes. The operation of practically all galvanometers is based upon the same principle, and they differ chiefly in mechanical construction and the relative arrangement of their different parts.

A very simple galvanometer, that will give quite satisfactory results, under favorable conditions, may be constructed as follows: Turn from a piece of hard wood a ring having dimensions corresponding to those given in the cross section, Fig. 1. Fill the groove in this ring to within 1/8 in. of the top with No. 18 gauge double-cotton-covered copper wire, insulating the different layers from each other by means of a layer of good bond paper. The winding may be started by drilling a small hole through the side of the groove, as close to the bottom as possible, and allowing about 6 in. of the wire to protrude through it. The outside end may be terminated in a similar manner, and the two ends should be on the same side of the ring, or as near each other as possible. A protecting covering of bookbinder's paper is placed over the winding and the completed ring given a coat of shellac. The electric current to be detected or measured is to pass around the winding of this coil and produce an effect upon a compass needle mounted in its center. In order that the current may produce a maximum effect upon the needle, the coil should be mounted in a vertical position.

The base upon which the ring is to be mounted may be cut from some 1/2-in. hard wood. It should be circular in form and about 5 in. in diameter, and have its upper edge rounded off and shellacked to improve its appearance. The ring is mounted in a vertical position on this base, which may be done as follows: Cut a flat surface on each of the flanges of the ring so that it will stand in a vertical position and the terminals of the winding will be as near as possible to the surface upon which the ring rests. Then form a stirrup from some thin sheet brass, similar to that shown in Fig. 2, so that it will fit tightly over the ring and its outwardly projecting ends will rest upon the base of the instrument. Small wood screws are used in fastening the stirrup to the base. The fastening may be made more secure by cutting a groove across the inside of the ring for the stirrup to fit in, Fig. 3, thus preventing the possibility of the ring moving through the stirrup. Two holes should be drilled in the base for the terminals of the winding to pass through, and it would be best to cut two grooves in the side of the ring for these wires so as to prevent their coming into contact with the metal stirrup. Two back-connected binding posts, A and B, Fig. 3, are mounted on the base and the ends of the winding attached to them. The wires should be placed in grooves cut in the under side of the base, and the screws used in fastening the binding posts should be countersunk.

A short compass needle is then mounted on a suitable supporting pivot in the center of the coil. This compass needle will always come to rest in an approximate north and south position when it is acted upon by the earth's magnetic field alone. If now the plane of the coil be placed in such a position that it is parallel to the direction of the compass needle (no current in the coil), the magnetic field that will be produced when a current is sent through the winding will be perpendicular to the magnetic field of the earth and there will be a force, due to this particular current, tending to turn the compass needle around perpendicularly to its original position. There will be a deflection of the needle for all values of current in the coil, and this deflection will vary in value as the current in the coil varies. The mere fact that the compass needle is deflected due to a current in the coil gives a means of detecting a current in any circuit of which the coil is a part, and the degree of this deflection affords a means of measuring the current, the value of the different deflections in terms of the current in the coil having been experimentally determined by sending a known current through the coil and noting the positions of the compass needle for each value of current used.

In order to determine the deflection of the needle, a scale, C, Fig. 3, must be mounted directly under the compass needle and a pointer, D, attached to the compass needle so that any movement of the needle results in an equal angular displacement of the pointer. The compass needle, E, should be short and quite heavy, say, 5/8 in. in length, 1/16 in. in thickness and 1/4 in. in width at its center, and tapering to a point at its ends. It should be made of a good grade of steel, tempered and then magnetized by means of a powerful electromagnet. The reason for making the compass needle short is that it will then operate in practically a uniform magnetic field, which exists only at the center of the coil. On account of the needle being so short and in view of the fact that it comes to rest parallel to the coil for its zero position, it is best to use a pointer attached to the needle to determine its deflection, as this pointer can be made much longer than the needle, and any movement of the needle may be more easily detected, as the end of the pointer moves through a much larger distance than the end of the needle, and since it may be attached to the needle, at right angles to the needle's axis, the end of the pointer will be off to one side of the coil and its movement may be easily observed. The pointer should be made of some nonmagnetic material, such as aluminum or brass, and it should be as long as it may be conveniently made. A suitable box with a glass cover may be provided in which the needle, pointer and scale may be housed. The construction of this box will be left entirely to the ingenuity of the one making the instrument.

In order to use this instrument as an ammeter, it will be necessary to calibrate it, which consists in determining the position of the pointer for various values of current through the coil. It will be necessary to obtain the use of a direct-current ammeter for this purpose. The winding of the galvanometer, ammeter, battery and a variable resistance of some kind should all be connected in series as shown in the diagram, Fig. 4. Allow the compass needle to come to rest under the influence of the earth's magnetic field and then turn the coil into such a position that it is as nearly parallel with the needle as possible. This corresponds to the zero position, and the instrument must always be in this position when it is used. The position of the ends of the pointer is now marked on the scale for different values of current, first with the current in one direction and then in the opposite direction. The deflection of the needle will, of course, reverse when the current is reversed.

The effect produced by any current upon the compass needle can be changed by changing the number of turns in the coil. In measuring a large current, a few turns of large wire would be required, and in measuring a small current, a large number of turns of small wire could be used. In other words, the size of the wire will depend upon the current it is to carry and the number of turns in the coil will depend upon the magnetic effect the current is to produce, which is proportional to the product of the number of turns and the current, called the ampere-turns.

Experiments with Camphor

Place a few scrapings from gum camphor in a tumbler of water and watch the phenomenon. The scrapings will go through all kinds of rapid motions as if they were alive. A drop of turpentine, or any oil, will stop their maneuvers. This experiment will show how quickly oil spreads over the surface of water.

Boiling Cracked Eggs

Eggs with the shells cracked can be boiled in the ordinary manner without danger of the white boiling out, if they are first wrapped in tissue paper. As soon as the paper becomes wet it will cling so tightly to the shell that the cracks are effectively closed.

A Trousers Hanger

A very serviceable hanger can be easily made of two clothespins of the clip type and about 2 ft. of large wire.

The wire should be bent into the shape shown at A with a loop about 1 in. in diameter as a hanger. The ends of the wire are slipped under the hooks on the sides of the clothespins, which are fastened to the trousers as shown in B.--Contributed by Olaf Tronnes, Evanston, Ill.

Removing Tight-Fitting Can Covers

Tight-fitting covers on lard and similar pails can be readily removed by tying a stout cord loosely below the cover, then placing an ordinary nail under the cord and twisting it. This will tighten the cord around the can evenly, which will loosen the cover.

A Skimming Spoon

A handy skimming spoon can be made very quickly of an ordinary spoon of any size desired. Slits are sawn across the bowl in the manner shown, using a hacksaw. The illustration is self-explanatory.--Contributed by G. H. Holter, Jasper, Minn.

How to Make Falling Blocks

Procure a thin board large enough to cut six blocks, 2 in. wide and 3 in. long; also 2 yd. of cotton tape, 1/4 in. wide, and some very small tacks. Cut the board into pieces of the size mentioned, and number two of them on both surfaces, 1, 2, 3, and 4. Cut off three pieces of tape, 4-3/4 in. long, and on the side of block 1 tack one piece of tape in the center at one end, and the other two pieces at each edge on the opposite end, all being on one side of the block as shown. Take the other block and lay the side numbered 4 up, then draw the two strips of tape on the edges of block 1 under it and back to the end of the surface on block 4, and tack them on this surface at the edges as shown. The center tape is passed under block 4 and turned over the opposite end and tacked. This is clearly shown in the sketch. Thus the second block will hang from either end of block 1 by simply folding them together and separating the ends.

Mark the sides of the third block 5 and 6, and place it with the two others so that the sides numbered 2, 3, and 5 will be up. Cut off three more pieces of tape, 4-3/4 in. long, and tack them on as shown, being careful not to tack through any of the first three pieces. Put on the fourth block in the same manner as the third block was attached to the second, and so on, until all the blocks are attached.

Take hold of the first block on the edges and tip it as shown by the arrow. The second block will then fall as shown by the second arrow, and the third block falls away in the same manner, and so on, down to the end.--Contributed by Wayne Nutting, Minneapolis, Minn.

Writing Name Reversed on Paper Placed on Forehead

The following is an entertaining experiment in a party of young people. One of those present is asked if he can write his name, and will, of course, answer "yes." He is then subjected to the following test: He is asked to sit down in a chair, a paper, folded several times, is placed on his forehead, a lead pencil is handed him and he is asked to write his name on the paper. As little time as possible to reflect should be left him; if he hesitates, he should be told to just go ahead, and in most cases it will be found that he starts writing his name at the left temple and, to the amusement of the others present, writes it in the way of many left-handed persons, that is, so that it is legible only when held in front of a mirror, unless one is practiced in reading reversed writing.

Use for an Old Table

An old table of the extension type, that may have a post broken, can be used against the wall in a kitchen as a work table. If there is a damaged part, that side is removed by sawing the crosspieces of the table in two and attaching it to the wall against the leaf which is turned in a reverse position.--Contributed by A. S. Thomas, Gordon, Can.

How to Make a Small Rheostat

In operating small motors there is as a rule no means provided for regulating their speed, and this often is quite a disadvantage, especially in the case of toy motors such as used on miniature electric locomotives. The speed, of course, can be regulated by changing the number of cells of battery by means of a special switch, but then all the cells are not used the same amount and some of them may be completely exhausted before the others show any appreciable depreciation. If a small transformer is used with a number of taps taken off the secondary winding, the voltage impressed upon the motor, and consequently the speed, can be changed by varying the amount of the secondary winding across which the motor is connected.

But in both these cases there is no means of varying the speed gradually. This can, however, be accomplished by means of a small rheostat placed in series with the motor. The rheostat acts in an electrical circuit in just the same way a valve does in a hydraulic circuit. It consists of a resistance, which can be easily varied in value, placed in the circuit connecting the motor with the source of electrical energy. A diagram of the rheostat is shown in Fig. 1, in which A represents the armature of the motor; B, the field; C, the rheostat, and D, the source of electrical energy. When the handle E is in such a position that the maximum amount of resistance is in circuit there will be a minimum current through the field and armature of the motor, and its speed will be a minimum. As the resistance of the rheostat is decreased, the current increases and the motor speeds up, reaching a maximum value when the resistance of the rheostat has been reduced to zero value. Such a rheostat may be used in combination with a special switch F., as shown in. Fig. 2. The switch gives a means of varying the voltage and the rheostat takes care of the desired changes in speed occurring between those produced by the variations in voltage.

A very simple and inexpensive rheostat may be constructed as follows: Procure a piece of thin fiber, about 1/16 in. thick, 1/2 in. wide and approximately 10 in. long. Wind on this piece of fiber, after the edges have all been smoothed down, a piece of No. 22 gauge cotton-covered resistance wire, starting about 1/4 in. from one end and winding the various turns fairly close together to within 1/4 in. of the other end. The ends of the wire may be secured by passing them through several small holes drilled in the piece of fiber, and should protrude 3 or 4 in. for connecting to binding posts that will be mounted upon the base of the rheostat.

Now form this piece of fiber into a complete ring by bending it around some round object, the flat side being toward the object. Determine as accurately as possible the diameter of the ring thus formed and also its thickness. Obtain a piece of well seasoned hard wood, 1/2 in. thick and 4-1/2 in. square. Round off the corners and upper edges of this block and mark out on it two circles whose diameters correspond to the inside and outside diameters of the fiber ring. The centers of these circles should be in the center of the block. Carefully saw out the two circles so that the space between the inside and outside portions will just accommodate the fiber ring. Obtain a second piece of hard wood, 1/4 in. thick and 4-3/4 in. square, round off its corners and upper edges and mount the other pieces upon it by means of several small wood screws, which should pass up from the under side and be well countersunk. Place the fiber ring in the groove, but, before doing so, drill a hole in the base proper for one end of the wire to pass through. Two small back-connected binding posts should be mounted in the corners. One of these should be connected to the end of the winding and the other to a small bolt in the center of the base that serves to hold the handle or movable arm of the rheostat in place. These connecting leads should all be placed in grooves cut in the under side of the base.

The movable arm of the rheostat may be made from a piece of 1/16-in. sheet brass, and should have the following approximate dimensions: length, 2 in.; breadth 1/2 in. at one end, and 1/4 in. at the other. Obtain a 1/8-in. brass bolt, about 1 in. long, also several washers. Drill a hole in the larger end of the piece of brass to accommodate the bolt and also in the center of the wooden base. Countersink the hole in the base on the under side with a 1/2-in. bit to a depth of 1/4 in. On the under side of the piece of brass, and near its narrow end, solder a piece of thin spring brass so that its free end will rest upon the upper edge of the fiber ring. A small handle may be mounted upon the upper side of the movable arm. Now mount the arm on the base by means of the bolt, placing several washers between it and the upper surface of the base, so that its outer end will be raised above the edge of the fiber ring. Solder a short piece of thin brass to the nut that is to be placed on the lower end of the bolt, and cut a recess in the countersunk portion of the hole in the base to accommodate it. When the bolt has been screwed down sufficiently tight a locknut may be put on, or the first nut soldered to the end of the bolt. If possible, it would be best to use a spring washer, or two, between the arm and base.

The insulation should now be removed from the wire on the upper edge of the fiber ring with a piece of fine sandpaper, so that the spring on the under side of the movable arm may make contact with the winding. The rheostat is now complete with the exception of a coat of shellac. A cross-sectional view of the completed rheostat is shown in Fig. 3.

Folding Arms for Clothesline Posts

The inconvenience of using a number of clothesline posts and the limited space available resulted in the making of a clothesline post as shown in the sketch. The entire line is supported on two posts, which should be about 6 in. square and are set in concrete. The upper ends of the posts are equipped with two arms, hinged to the sides of the posts in such a manner that the inside ends of the arms will meet on top of the post when they are in a horizontal position. Each arm is provided with three wood pins, equally spaced for the line. The arms are supported in a horizontal position by two bars of metal at the center, as shown. Holes are bored into the sides of the posts to receive the pins when the arms are at rest.

A small box is fastened to one post, to provide a place for the clothesline and the clothespins. The line, when put up, gives space for an entire washing without the use of a prop, as the line can be drawn taut enough to hold the garments.--Contributed by Olaf Tronnes, Evanston, Ill.

A Folding Bookrack

Having need of a bookrack which I could pack away in my trunk and still have room for my clothes, I made one as follows: I procured a piece of pine, 5/8 in. thick, 6 in. wide and 18 in. long, and laid out the plan on one side. Holes were drilled in the edges, 3/4 in. from the ends, to receive 1-1/2-in. round-head brass screws. The design for the ends was sawn out with a scroll saw and the edges smoothed up with fine sandpaper, whereupon the surfaces were stained and given a coat of wax. The screws were put in place to make the ends turn on them as on a bearing. In use the ends were turned up.--Contributed by Spencer Hall, Baltimore, Maryland.

A Simple Balance

Having use for a balance in a laboratory and being unable to procure any scales at the time, I hastily rigged up a device that served the purpose as well, as the work did not require very great precision. An elastic band and a short piece of string was procured and the band cut open. The string was then fastened around the beaker as shown, and the whole suspended from a shelf.

Into the beaker was then poured 100 cubic centimeters of water and the stretch of the elastic band noted by the displacement of a knot in the string in respect to the scale on a graduate, placed beside the beaker. The length of the elastic was then changed until the knot was exactly opposite the 100-division mark on the graduate scale. Then, since the elongation of the elastic band follows Hook's law, the extension of the band to the amount of one scale division means an added weight of one gram in the beaker.--Contributed by L. Horle, Newark, New Jersey.

An Ink Eraser

A good knife eraser for ink can be made from a discarded or broken ruling pen. One of the parts, or nibs, is cut off close to the handle and the remaining one sharpened on both edges at the point. This instrument is better than a knife or the regular scratcher, because the cutting edge will shave the surface of the paper or tracing cloth and not roughen or cut it. Erasing done with this knife will readily take ink without further preparation of the surface.--Contributed by Warren E. Crane, Cleveland, O.

Gate Fasteners

Buttons on gates or small doors are apt to become loose and then drop down, thereby allowing the gate or door to become unfastened. The ordinary button is shown at A where it is loose and turned by its own weight. If the button is cut as shown at B, it will remain fastened, even if it is loose on the screw or nail.--Contributed by A. S. Thomas, Amherstburg, Ont.

A Compensating Siphon

The homemade siphon shown in the sketch consists of two rubber corks and a glass tube with a rubber hose connected to it. The cork A is used as a bearing and support on the edge of the tank. The position of the cork B on the tube determines the distance that the mouth of the tube will be under the surface of the liquid, also to some extent the sensitiveness of the apparatus. However, the principle of the device is the buoyant effect of the water and the lever action of the rubber tube which is attached.

The one that I made had a tube 14 in. long, and the cork B was 1-3/4 in. in diameter, 1 in. thick, and weighed about 1/10 of a pound. The practical application of this siphon will be found in sieve tests where it is necessary to collect the residue on the bottom of the tank while drawing off the liquid at the surface, also in oil-storage tanks where it is not wished to disturb the dirt or other residue which collects on the bottom of the tank.--Contributed by James Hemphill, Jr., Duquesne, Pennsylvania.

A Polarity Indicator

Lines in a cable or the ends of connections at a distance from the battery must be tested to determine the polarity. Where a large amount of this work is to be done, as in automobile and motorboat repairing, it is necessary to have an indicator to save time. A cheap indicator for this purpose can be made of a 6-in. test tube having its ends sealed and inclosing a saturated solution of ammonium chloride (sal ammoniac) and water. The sealed ends are made by inserting a piece of wire through a cork and, after forcing this tightly into the end of the test tube, covering it with sealing wax.

To use, connect the terminals to the battery lines, and the end of the wire in the solution giving off bubbles is the negative wire.--Contributed by H. S. Parker, Brooklyn, N. Y.

Small Steam-Engine Cylinders Made from Seamless Brass Tubing

In making a small steam engine it was desired to use seamless brass tubing for the cylinders. To have them exactly alike a piece of tubing of the right size and of sufficient length for both cylinders was fitted on a wood mandrel, A, and the ends trued up in a lathe. As these cylinders were to fit into holes bored in a steel bedplate, it was necessary to have a flange at one end. A groove was turned in the tubing B in the center, and as a final operation a parting tool was used on the line CD. This resulted in a pair of cylinders flanged to fit the bedplate.--Contributed by Harry F. Lowe, Washington, D. C.

A Pocket Direct-Current Voltmeter

The assembled drawings of a very simple voltmeter are shown in Fig. 1, and its operation is as follows: The moving portion consists of a pointer, or needle, A; a small permanent magnet, or armature, B, and a counterweight, C, mounted upon a small steel shaft, D. The ends of this steel shaft are pointed and rest in bearings provided in the U-shaped piece of brass E, which is rigidly fastened to the fiber base F, by means of two screws. The permanent magnet B, carried on the shaft D, is at all times under the magnetic influence of the permanent horseshoe magnet, G, which is fastened, by means of thin brass straps, H H, and small screws, to the base F, so that the ends of the armature B are directly above the poles of the horseshoe magnet. The armature B will assume the position shown in the sketch when it is acted upon by the permanent magnet G alone and the moving system is perfectly balanced. A solenoid, J, is mounted in the position shown. When there is a current in its winding its soft-iron core will become magnetized and the magnetic pole produced at the lower end will produce a magnetic force upon the armature B, with the result that the armature will be rotated either in a clockwise or counter-clockwise direction, depending upon its polarity and the polarity of the end of the core adjacent to it. Thus, if the left end of the armature has north polarity, the right end south polarity, and the lower end of the core is magnetized to a south polarity the armature will be rotated clockwise, for the left end, or north pole, will be attracted by the lower end of the iron core, which is a south pole, and the right end will be repelled. This is in accordance with one of the fundamental laws of magnetism which states that magnetic poles of unlike polarity attract each other and those of like polarity repel each other. The amount the armature B is rotated will depend upon the relative effects of the pole of the solenoid and the permanent magnet G. The strength of the pole of the solenoid will depend upon the current in its winding and the number of times the current passes around the core, or the number of turns in the winding. In other words, the strength of the pole of the solenoid varies as the product of the current and the number of turns, which is called the ampere-turns. The same magnetic effect can be produced by a large current passing through a few turns or a small current passing through a relatively large number of turns. This simple relation of current and turns gives a means of adjusting the current capacity of the instrument so that a full-scale deflection of the needle will correspond to any desired maximum current. The instrument may be used as either a voltmeter or as an ammeter, and its operation will be identical in each case. The resistance of the voltmeter, however, will be many times the resistance of the ammeter, as it will be connected directly across the line, while the ammeter will always be in series in the circuit in which it is desired to measure the current. The following description and suggestion as to how to proceed in the construction of this instrument may be useful to those who undertake to build one. All the minor details and some of the dimensions will be omitted in the description, but these can be easily supplied.

Procure a piece of hard rubber or fiber, about 1/4 in. in thickness and of sufficient size to cut from it a disk, 2-1/2 in. in diameter. Make a small horseshoe magnet from a piece of the very best steel obtainable, and magnetize it to as high a strength as possible. This magnet is made of a piece of steel, 1/8 in. thick, about 3/8 in. in breadth, and of such length that the overall lengthwise dimension of the completed magnet will be about 1-7/8 in. and the distance between the inside edges of the ends a little greater than 1/2 in. Fasten the completed magnet to the base F by means of two or three straps, made from some thin brass, and small machine or wood screws.

Then cut from some 1/16-in. sheet brass a piece having the general appearance and dimensions shown at A, Fig. 2. Bend the ends of this piece over at right angles to the center portion along the dotted lines. Drill the hole at the upper end and thread it for a 1/16-in. machine screw. By means of a pointed drill, make a small recess at the lower end directly opposite the first hole. This small recess is to form the lower bearing for the shaft supporting the moving system, while a small recess cut centrally in the end of a screw, mounted in the upper hole, will form the upper bearing. The screw placed in the upper hole need be only about 3/16 in. long. The holes in the two wings are for mounting this piece upon the fiber base, as shown in Fig. 1.

The shaft for supporting the moving system is made of a piece of a hatpin. It is about 13/16 in. long and its ends are pointed so that they will turn freely in the bearings provided for them.

The armature is cut from a piece of 1/16-in. sheet steel. It is made about 3/4 in. long, 5/16 in. wide at the center, tapering to 1/8 in. at the ends. A hole is drilled in its center so that it may be forced onto the shaft. It is mounted so that its lower surface comes about 1/4 in. from the lower end of the shaft.

Then cut from some very thin brass a piece, that is to form the needle, 1/4 in. wide at one end and tapered to a point at the other, the total length being about 3 in. Drill a hole in the large end of this piece, the same size as the shaft and 1/2 in. from the end. This piece is not fastened to the shaft until some of the other parts are completed.

The spool upon which the winding is to be placed is made as follows: Procure a piece of very soft wrought iron, 1-1/4 in. long and 1/4 in. in diameter, to form the core. The ends of the spool are made of thin brass and are dimensioned as shown in Fig. 2, at B and C. The piece shown at B is to form the lower end of the spool, and is bent at right angles along the dotted line. The two holes at the lower edge are for attaching the end of the spool to the fiber base. The piece shown at C forms the upper end of the spool and at the same time a back upon which the scale of the instrument is mounted. The holes in the lower edge are threaded for small machine screws, as it will be necessary to fasten this piece to the base by means of screws that pass through the base from the under side, as shown in Fig. 1. Bend the upper and lower portion of the piece over at right angles to the center portion along the dotted lines. Make sure that the large hole in the center of each end piece is of such size that it will fit very tight on the end of the wrought-iron core. Force the end pieces onto the ends of the core a short distance, say, 1/16 in., and hammer down the edges of the core so that the end pieces cannot be easily removed. In fastening the ends to the core be sure that the parts that are to rest upon the base are parallel with each other and extend in opposite directions; also that the ends are at right angles to the core. Then insulate the inner portions of the completed spool with several thicknesses of onion-skin paper, or any good-quality, thin writing paper, and shellac. The winding will be described later.

Mount the spool and support for the bearings upon the base so that they occupy the positions, relative to each other, indicated in Fig. 1. A paper scale is then mounted upon the brass base provided for it by means of some thin shellac. The upper and lower lines for the scale can now be drawn upon the paper, using the center of the screw at the lower end of the needle as a center. These lines are best placed about 1/8 in. apart and not nearer the edge of the base than 1/4 inches.

The needle is bent over at right angles 5/16 in. from the center of the shaft. Another right-angle bend in the needle is then made so that the pointed end will be about 1/16 in. above the surface of the scale when the large end of the needle is fastened to the shaft 3/8 in. from the upper end of the latter. Turn the needle on the shaft so that the pointer is at the left end of the scale when the moving system is at rest. The shaft must be exactly vertical when this adjustment is made. Cut the end of the needle down until its end is midway between the two scale lines. Solder the needle to the shaft, and then place a sufficient quantity of solder on the broad end to balance the system perfectly and allow it to come to rest in any position when the armature B is not influenced by any magnetic field.

A containing case for the instrument may be made as follows: Make a cylinder from some thin sheet brass, having exactly the same inside diameter as the base, and a height a little greater than the vertical distance from the lower surface of the base to the upper surface of the needle. Also a disk from some thin sheet brass, having a diameter 1/8 in. greater than the outside diameter of the cylinder. Round off the edges of this disk and cut a curved slot in it directly over the scale, about 3/8 in. wide and of the same length and form as the scale. Solder the disk to one end of the cylinder, placing the solder all on the inside. To prevent moisture from entering the case, fasten a piece of thin glass on the under side of the slot in the disk by means of some shellac and several pieces of brass soldered to the disk and bent down onto the glass. The case can now be fastened to the base by means of several screws, passing through its lower end into the edge of the base. Two small binding posts are mounted on the outside of the case, about 90 deg. apart and well insulated from each other and from the case, to serve as terminals for the instrument.

The instrument is now complete with the exception of the winding. Since this is to be a voltmeter and it is always desirable that a voltmeter take as small a current as possible, the winding must consist of a relatively large number of turns of small wire, each turn carrying a small current. The difference in the construction of different instruments necessitates that their winding contain a different number of turns in order that a given voltage may produce a full-scale deflection. A little experimenting with different windings is the easiest means of determining the proper size of wire and number of turns to meet individual requirements. After adjusting the winding so that the maximum voltage it is desired to measure produces a full-scale deflection, the scale is calibrated by marking the positions of the needle in accordance with those of the needle of a standard instrument connected in parallel with it. In marking the scale of an ammeter, connect the instruments in series. Remember that if the instrument is to be used as an ammeter, it must have as low a resistance as possible and that to prevent undue heating, the wire must have ample cross section.

If difficulty is experienced due to the continuous vibration of the needle, although the current be practically constant, this trouble can be greatly reduced by mounting a paper wind vane on the moving system, which will tend to dampen its movement.

Falling Leaves in a Nature Scene

Use an ordinary pasteboard box, a shoe box or larger, and cut out one end. Fasten the box to the ceiling by means of pasteboard strips. One end of these strips is pasted on the bottom of the box and the other ends tacked to the ceiling. Fit a piece of board, 1/2 in. thick, into the open end of the box so that it will slide easily back and forth on the inside. Place this slide in the back of the box, attach a string to it and run this through double tacks placed in the ceiling and to the side wings.

Have the box almost full of autumn leaves, and when the slide is pulled slowly by the operator, they will be pushed, one or two at a time, out of the open end, and will drift down to the stage as naturally as if falling from trees, making quite a realistic scene.--Contributed by Miss S. E. Jocelyn, New Haven, Conn.

Home or Traveling Utility Bed Pocket

The pocket is made of cretonne with wire hooks attached on the upper edge. The compartments are arranged as needs may require. It can be hooked on the head, foot or side rail of the bed or used, as shown, in a sleeping car. It provides a place to keep the slippers, gown and other necessities, and can be rolled up and put in a bag.--Contributed by Harriette I. Lockwood, Philadelphia, Pa.

A Paper Perforator

In an emergency an ordinary hacksaw blade may be made to serve very acceptably as a paper perforator. The toothed edge is applied to the paper and the reverse edge tapped with a mallet or hammer. A considerable number of sheets may be perforated at one time, depending of course on the thickness and softness of the paper.

Turning Brass Rings

Occasionally an amateur has need of brass rings of round cross section, and if their construction is not understood, the task is a difficult one. If a piece of brass tubing, an old bushing or a cored piece is at hand, a part of the work is already done. If not, a piece of stock with large enough outside diameter should be chucked in the lathe and drilled out with the right size of drill. A tin or pasteboard template should be prepared the size of the ring section--a half circle is best, and it is easiest made by drilling a hole in the tin and cutting it in two. An inside boring tool and a turning tool are necessary. It is preferable to shape the inside first, cutting it out roughly and checking up with the template. The amount of inside cutting is shown in the drawing. A hard scraper and emery cloth may be used for smoothing and polishing.

Turn and polish the outside and finally turn as far down on the inner quarter as can be done without cutting off the finish, then polish and cut it off. It only requires a little filing to smooth up the rim of rough metal left.

An Electric Fountain By Walter P. Butler

To make the grounds as attractive as possible for a lawn party given one night, I constructed an electric fountain which at first appeared to be an expensive proposition, but when completed the desired effect was produced without any expense whatever, as I had the things used in its construction on hand.

A light frame, 9 in. square, was made, of 3/4-in. material, as shown in Fig. 1, and a grooved pulley was attached exactly in the center on the under side of the crosspiece. A turned stick, A, 2 in. in diameter and 2-1/2 in. long, was fastened to the face of the pulley so that it turned true as the pulley and frame revolved. A hole was then bored centrally through the three parts, the frame crosspiece, the pulley, and the turned stick, of a size to fit a spindle about 3/8 in. in diameter.

A box was procured, large enough for the frame to turn in freely, and a block of wood was fastened centrally in its bottom, which had a 3/8-in. pin set in a hole bored in the center. The pin may be of hard wood, but it is better to use metal. A bolt, or piece of rod, will answer the purpose of a pin very well.

A small battery motor--I had one on hand and did not need to purchase one--was fastened to one side of the box so that its pulley was in line with the pulley on the lower surface of the frame. The batteries to run the motor were placed in the corner of the box, where the revolving frame would not touch them. The motor may be of larger current capacity, however, and run direct on the current used for the lamps.

About 1/2 in. from the lower end of the turned piece A, a brass strip was fastened around it. This work should be neatly done, and the joint soldered and smoothed, so that the outer surface will not catch on the brush used to make the contact. This ring can be better made by cutting the width from a piece of brass tubing of a size to fit on the turned stick A. About 1-1/2 in. from the lower end four segments of a circle were fastened so as to make a space of about 1/4 in. between their ends. This construction is clearly shown in Fig. 2. A cross section, showing the wire connections from the brass ring and segments to the lamps and where they lead out on top, is shown at B. The contact brushes consist of brass strips fastened with bolts to an upright, C, made of wood and attached to one edge of the block in the bottom of the box. Two nuts are used on each bolt, between which are fastened the lead wires from a source of current.

The wiring diagram is shown in Fig. 3. The wire D from the ring is run to the brass base of each lamp, of which there are four. The wires E, from each segment, are connected with solder to each screw ferrule of the lamps, and the ends are left bare and open, as shown, between the lamps.

A lamp is fastened to each corner of the frame on top, as shown in Fig. 4, with a piece of wire wrapped once around the screw ferrule and the extending ends held with staples. The wire used should be heavily insulated or, if it is of iron, a rubber tube slipped over it. A piece of tin, or bright metal, is placed beneath each globe for a reflector.

A glass plate was used to cover the box, and a lawn spray of the fountain type was placed on the glass. The globes, as they light beneath the spray, illuminate the top and the light follows the streams of water so that they appear like streams of light. Each light is turned on in succession as the frame revolves within the box, and by using globes of different colors, an exceedingly beautiful effect is obtained. If the bared ends of the wires are twisted together between the globes, these will all glow at once.

A Mystery Coin Box

The effect of this trick is as follows: A small metal box, just large enough to hold a half dollar and about 1/2 in. high, with a cover that fits snugly over the top, is passed out to be examined, and when handed back to the performer he places it on the finger ends of his left hand, and a half dollar is dropped into it and the cover put on. The box is then shaken to prove that the coin is still there. The performer then taps the box with his fingers and picks it up with the other hand and the coin will appear to have fallen through the bottom. Both the coin and box are then handed out for examination.

This seemingly impossible effect is made when the performer places the cover on the box. The box is resting on the fingers of the left hand and the cover is held between the thumb and forefinger of the right hand, but just before placing the cover on, the box is turned over with the right thumb, and the cover is placed on the bottom instead of the top.

The trick can be done within a foot of the spectators without their seeing the deception. It is a good plan to hide the box with the right hand when placing the cover, although this is not necessary.

How to Make a Small Series Motor

The motor here described has been constructed and found to give very good results. It is simple to build and the materials required can be easily obtained. The armature core and field, or frame, are made of laminated iron, instead of being cast as is often done by the manufacturers, which is a decided advantage, as certain losses are thereby reduced, and its operation will be improved by this type of construction especially if used on an alternating-current circuit.

The machine will be divided into three main parts, the construction of each of which will be taken up in turn and the method of procedure discussed in detail. These parts are the completed armature, the field and bearings, and the brushes together with suitable terminals and connections.

The armature core is constructed from a number of pieces, having dimensions that correspond to those given in A, Fig. 1. These pieces are cut from thin annealed sheet iron, in sufficient number to make a pile, 3/4 in. high, when placed on top of each other and firmly clamped. It would, no doubt, be best to first lay out one of these pieces very carefully and then cut it out and mark out the other pieces with the first one as a pattern, being careful to file off all the rough edges on each piece.

Now obtain a piece of 1/4-in. iron or brass rod, 3-1/4 in. long, that is to serve as a shaft upon which to mount the armature and commutator. This rod is threaded for a distance of 7/8 in. on one end and 1-7/8 in. on the other. Procure five brass nuts, 1/8 in. thickness, to fit the threads on the rod. If possible have the ends of the rod centered before the threads are cut, for reasons to be given later. Place one of the nuts on that end of the shaft that is threaded for 7/8 in., and in such a position that its inner surface is 3/4 in. from the end of the rod. Solder this nut to the rod when it is in the proper place and remove all extra solder. Drill a 1/4-in. hole in each of the armature stampings and place them on the shaft, clamping them together with three small clamps, one on each extension or pole. Then place a second nut on the shaft and draw it up tight against the last stamping placed in position, and solder it to the shaft. Next wind two or three layers of good strong tape around each of the rectangular portions of the armature and then remove the clamps. Make sure that all the edges of the different laminations are perfectly even before applying the tape.

The shaft is then placed between two centers to determine whether the core is approximately balanced and runs true. If the armature core is unbalanced or not true, the trouble should be corrected before proceeding with the remainder of the armature construction. The armature winding is not to be put on the core until the commutator has been constructed and mounted on the shaft.

The commutator consists of three pieces of thin sheet brass similar to that shown at B, Fig. 1, mounted on the surface of a cylinder of insulating material, 3/8 in. long and 7/8 in. in diameter. A 1/4-in. hole is drilled lengthwise through the cylinder of insulating material. Bend the pieces of brass around the outside of the cylinder, and turn all the lugs, except the center one, marked C, over at right angles and put a small nail or screw through the holes in the ends of the lugs into the cylinder. These pieces of brass are equally spaced around the cylinder so that all the lugs, not turned down, project in the same direction. Now place a nut on the end of the shaft that extends the greatest distance through the armature, so that its outside surface is 1/2 in. from the surface of the end of the armature core next to it, and solder the nut to the shaft. Place the commutator on the shaft so that the projections on the pieces of brass are toward the armature core and the spaces between the ends of the pieces occupy the position relative to the cores, shown at A, Fig. 2. Another nut is then placed on the shaft and drawn up tight against the cylinder. The proper spacing of the various parts on the shaft of the machine is shown at D, Fig. 1. Another small nut is placed on the end of the shaft, away from the commutator, so that its outside surface is 1/2 in. from the surface of the end of the armature core.

The threads on that part of the shaft extending beyond the last nut on each end are now filed off, which can be easily done by placing the shaft between the centers of a lathe and revolving it quite rapidly, the file being applied to the parts that are to be cut down.

Obtain a small quantity of No. 22 gauge single-cotton-covered copper wire and wind four layers on each of the three legs, or poles, of the armature core, insulating the layers from each other and the entire winding from the core by means of paper and shellac. The three coils are wound in the same direction about their respective cores and each winding is started at the center of the armature with 2 or 3 in. of wire extending out toward the commutator. The outside end of each winding will terminate at the end of the coil toward the center of the armature, if an even number of layers is wound on, and is securely fastened by means of two or three turns of heavy thread. The inside end of one coil is then connected to the outside end of the next one, and so on. These connections can be easily made, and at the same time the proper connections made to the commutator, by cutting the inside end of one coil and the outside end of the next so that they will reach the lug on the nearest segment of the commutator, with about 1/4 in. to spare, then removing the insulation from each for about 1/8 in. and soldering them both to the same lug. The arrangement of the winding is shown at A, Fig. 2. Connect all of the coils and segments in this manner, and the armature of the motor is complete.

The field or frame of the machine is made from a number of laminations whose dimensions correspond to those given in B, Fig. 2. As many laminations are used in the construction of the frame as the number of pieces in the armature, if iron of the same thickness is used. Four of the laminations have extensions at their lower corners to correspond to the parts shown by the dotted lines in B, Fig. 2. Place all of these laminations in a pile and clamp them rigidly together, then drill the four holes, indicated by the letters C, D, E and F, with a 3/16-in. drill. Two of the pieces with the extensions on them are placed in the bottom of the pile and the other two on top.

Place a 3/16-in. bolt through each of the lower holes and draw up the nuts on them tight. Procure two pieces of 3/16-in. rod, 1-1/2 in. long, and thread each end for a distance of 1/2 in. Get 8 nuts for these rods, about 1/8 in. thick and 5/8 in. across the face, if possible. Both sides of these nuts are filed down flat. Put the threaded rods through the two upper holes in the field frame and place a nut on each end and draw them tight, leaving an equal length of rod protruding from each side.

Obtain two pieces of 1/8-in. brass, 5/8 in. wide, one 4-3/4 in. long and the other 5-3/4 in. long. Bend these pieces into the forms shown at A, Fig. 3. Drill a 3/16-in. hole in each end of both pieces so that they may be mounted upon the ends of the rods protruding from the field frame. The exact center of the space the armature is to occupy is then marked on each of these pieces, and a hole is drilled in each, having the same diameter as the ends of the armature shaft.

The extensions on the outside laminations are bent over at right angles to the main portion of the frame, thus forming a base upon which the motor may rest. Holes may be drilled in the extensions after they are bent over to be used in mounting the frame upon a wooden base.

Procure about 1/2 lb. of No. 18 gauge single-cotton-covered copper wire and wind it on the lower center portion of the frame until the depth of the winding is about 1/2 in. Be careful to insulate the winding well and, to insure mechanical protection, place a layer of adhesive tape outside. About 4 or 5 in. of wire is allowed at each end for making connections. It is best to have these ends terminate on the commutator side of the frame.

The brushes for the machine are made from some thin sheet copper or brass, and are shaped and dimensioned approximately as shown at B, Fig. 3. Two pieces of hard rubber, or fiber, 1/2 in. square and 7/8 in. long, serve as mountings for the brushes. These pieces of insulation are mounted in the corners of the armature support, at the commutator end, by means of two small screws in each. Mount the brushes on these pieces so that their free ends bear on the commutator exactly opposite each other. One brush is mounted on the upper end of its support and the other brush on the lower end of its support. This is shown at C, Fig. 3. Two small binding posts are mounted at the same time as the brushes, and are electrically connected to the brushes, thus affording an easy means of making a connection to the armature. The brushes are so mounted as to bear firmly upon the commutator.

To operate the motor, connect the armature and field windings in series, and the combination to a source of electromotive force of several volts. If it is desired to reverse the direction of rotation, reverse the connections of either the armature or field windings, but not both. The motor may be mounted on a neat wooden base and the connections all brought down to a reversing switch, which may also be mounted on the same base as the motor. The speed can be varied by changing the impressed voltage, or by connecting a variable resistance in the armature circuit, such as a wire rheostat.

A small pulley may be made and attached to the armature shaft so that the motor may be used in driving various kinds of toys.

Cooler for Milk and Butter

An earthen jar or crock, with a cover, set in a box containing moist sand will keep butter and milk in hot weather better than a refrigerator. The sand must be kept moist at all times.--Edwin J. Bachman, Jr., Fullerton, Pa.

Rubber Bumper on a Water Faucet

Sometimes a dish is broken by striking it on the faucet. This is easily remedied by cutting a rubber washer from a rubber-boot heel with a sharp chisel and a hammer. The washer is pushed into place on the end of the faucet, and the dishes may strike the rubber without being broken.--Contributed by Harriette I. Lockwood, Philadelphia, Pa.

Boring a Clean-Edged Hole

When boring a hole in wood, withdraw the bit as soon as the worm shows, then start the worm in the hole on the opposite side and finish boring the hole. It will then have clean edges on both sides of the wood. Often the bit pushes splinters of wood ahead of it, when passing through, but by using the method described this is avoided.

Drilling Thin Metal

In drilling very thin stock the drill, if not properly ground, will tear the metal and leave a ragged edge. To cut a hole through neatly the drill should be ground as illustrated. The center A should extend about 1/64 in. beyond the points B. The point A locates the center and the sharp points B cut out the disk of metal. Holes have been neatly and quickly made with this drill grinding in metal measuring .002 in. thickness.--Contributed by Joseph J. Kolar, Maywood, Ill.

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A pencil may be kept from falling out of the pocket by wrapping a couple of turns of tape around it or by wrapping it with a small rubber band.

Flexible-Cord Adjuster for an Electrical Flatiron

When using an electrical flatiron the flexible cord frequently gets under the iron, causing much trouble for the user, and mussing up the clothing. The cord can be kept out of the way by fastening a pulley to the ironing board and attaching a coil spring to the electric cord between the pulley and the electric-fixture socket. A coil spring that will draw out about 3 ft. should be used.--Contributed by Herbert Blandford, Elmira, N. Y.

A Wood Clothes Peg

If clothes that are slightly damp are hung on a nail or metal peg, a rust stain that is almost impossible to remove will be the result. To prevent this, drive a nail with the head removed into the wall or cleat, and place a wood peg over it. The peg may be turned up or whittled out with a pocket knife and the hole bored with a hand drill.--Contributed by Wm. A. Robinson, Waynesboro, Pa.

To Make Scratch Pads of Old Labels

Labels and blank paper of uniform size, that would otherwise be cast aside, can be turned into handy scratch pads by placing them between blocks of wood, secured by a wood clamp, and applying paste on two edges, then pressing a strip of paper on the pasted portions. The edges to be pasted should project a trifle beyond the edges of the blocks.

How to Make an Electric Heater

The electric heater described in this article is very simple to construct, its operation exceedingly satisfactory, and the necessary material easily procured at a small cost at most electrical-supply stores. The few tools needed are usually found about every home, and the heater may be constructed by any ingenious person.

Procure 6 porcelain tubes, 20 in. long and approximately 13/16 in. in diameter. On each of these tubes wind 25 ft. of bare No. 26 gauge "Climax" resistance wire. The various turns should be uniformly distributed along the tubes and not allowed to come into contact with each other, which can be prevented by placing a thin, narrow coat of plaster of Paris along the side of each of the tubes immediately after the winding has been put on. Several inches of free wire should be allowed at each end, for making connections, and the first and last turns on each tube should be securely fastened to the tube by several turns of binding wire. It would be best not to extend the winding nearer the ends of the tubes than 3/4 in.

Cut from some heavy tin, or other thin sheet metal, two disks, 6 in. in diameter, and punch six 5/16-in. holes in each of the disks at equal distances and within 3/4 in. of the outer edge. Punch two 1/8-in. holes in one of these disks, to be used in mounting a porcelain socket, and also one 1/2-in. hole through which the wires may be led to the socket, as shown in Fig. 1. In the other disk punch four 1/8-in. holes, for mounting two porcelain single-pole snap switches, and two 1/2-in. holes, for leading the wires through to the switches, as shown in Fig. 2.

Cut off six lengths of 5/16-in. iron rod, 22 in. long, and thread both ends of each piece for a length of 1-1/4 in. Fasten the porcelain tubes between the metal disks, by placing one of the rods through each of the tubes and allowing the ends to extend through the 5/16-in. holes in the outer edge of the disks. A nut should be placed on each end of all the rods and drawn up so that the length of rod protruding at each end is the same. Obtain two single-pole snap switches and a porcelain socket, and mount them on the ends by means of some small stove bolts.

The windings on the porcelain tubes should be connected as follows: Let the windings be designated by the letters A, B, C, D, E, and F, and their position be that indicated in Figs. 1 and 2. The primes indicate the ends of the windings at the socket end, and the letters without the primes indicate the ends of the windings at the switch end of the heater. The ends A and D should be connected directly together. The ends B and C to the clips of the right-band snap switch, and E and F, to the clips of the left-hand snap switch. The ends F, A, and B should be connected to one terminal of the socket, and C, D, and E to the other terminal of the socket. Electrical connection is made to the winding by means of a plug and piece of lamp cord. It is obvious that the windings A and D will be connected as soon as the plug is screwed into the socket, if the circuit is closed at all other points, and the windings B and C, and E and F are controlled by the right and left-hand snap switches, respectively. Make sure all the connections are properly insulated, and that there is little chance of a short circuit occurring.

After the socket and snap switches have been connected to the windings, two more thin disks, the same diameter as the first, may be fitted over the ends and held in place by two units on the end of each rod, a nut being placed on each side of the disks. A better way of mounting these disks would be by small machine screws that enter threaded holes in the ends of the rods. These last disks are not absolutely necessary, but they will add some to the appearance of the completed heater. Four small ears, about 5/8 in. square, should be cut on the outer edge of the outside or inside disks and bent over at right angles to the main portion, to be used in mounting the outside case of the heater.

Cut from a sheet of 1/8-in. asbestos a piece just long enough to fit between the inside disks and wide enough to cover the three lower windings C, D, and E. The object of this piece of asbestos is to protect the surface upon which the heater will stand from excessive heat, since it is to rest in a horizontal position.

Obtain a piece of perforated, thin sheet metal, 19-1/2 in. wide and long enough to reach from one outside disk to the other. Bend this into a cylinder and fasten it to the lugs on the disks by means of small screws or bolts.

The legs may be made of 1/8-in. strap iron, 5/8 in. wide, bent into the form shown in Fig. 3. These pieces may be attached to the perforated cylinder, before it is mounted on the heater proper, by means of several small bolts. The piece of asbestos should be wired to the cylinder after the heater is all assembled, so that it will always remain in the lower part of the cylinder and serve the purpose for which it is intended.

The heater, as described above, is constructed for a 110-volt circuit, which is the voltage commonly used in electric lighting. The total consumption of the heater will be approximately 600 watts, each part consuming about 1/3 of the total, or 200 watts. If it is desired to wind the heater for a 220-volt circuit, 25 ft. of No. 29 gauge "Climax" resistance wire should be used on each tube.

A Molding-Sawing Block Used on a Bench

Having occasion to saw some short pieces of molding, I experienced considerable trouble in holding them without a vise until I made a block, as shown in the sketch. This answered the purpose as well as a vise. The block is not fastened in any manner, but is simply pushed against the edge of the bench or table and held with the hand. It should be about 9 in. wide and 1 ft. long, with strips 2 in. thick at each edge.--Contributed by W. F. Brodnax, Jr., Bethlehem, Pa.

Pipe Caps Used as Castings for Engine Pistons

Desiring to make a small piston for a model engine and not caring to make a pattern and send it away to have a casting made, I thought of using ordinary pipe caps, these being both inexpensive and of a quality adapted to machining.

The cylinder bore was 1-1/2 in. in diameter, so I secured a standard pipe cap for 1-1/4-in. pipe which gave an outside diameter of about 1-5/8 in. The cap, not having sufficient depth for holding in a chuck, was screwed on a short piece of pipe and then trued in the lathe chuck. The outside surface was turned to a diameter of 1-1/2 in., then removed from the pipe, reversed and chucked again, and the threads bored out to reduce the walls to 1/8 in. This made an excellent piston for a single-acting engine.--Contributed by Harry F. Lowe, Washington, D. C.

An Electric Horn

A simple electric horn for use on a bicycle, automobile, or for other purposes, can be constructed as shown in Fig. 1. The size will of course depend somewhat on the use for which it is intended, but one with the diaphragm 1-3/4 in. in diameter and the horn 5 in. long and 4 in. in diameter, at the large end, will be sufficient for most purposes. This will make the instrument 7-1/2 or 8 in. in over-all length.

The horn proper, A, Fig. 1, is constructed first. This can be formed from sheet brass. To lay out the metal to the desired size draw a cross section, as ABCD, Fig. 2, then project the lines AC and BD until they meet at E. Strike two arcs of circles on the brass sheet, using EC as radius for the inner one and EA for the outer. Measure off FG and HJ equal to 3-1/4 times DC and AB, respectively, and cut out FGJH. Roll and lap 1/4 in. at the edges and solder the joint neatly.

After smoothing the edges on the ends, solder a very thin disk of ferrotype metal, B, Fig. 1, to the small end of the horn. This is used for the diaphragm. Cut out a ring, C, from 1/4-in. hard fiber and bevel it on the inside edge to fit the horn. Also make a disk of fiber, D, having the same outside diameter as the ring C. These parts form the ends for a brass cylinder E, which is made in two parts or halves joined on the lines shown in Fig. 3. Fasten one of the halves, F, Fig. 3, to the fiber ring C and disk D, Fig. 1, with small screws, the other half to be put in place after the instrument is completed and adjusted.

A small support, G, is cut from fiber and fastened in as shown. A pair of magnets of about 50 ohms are mounted on this support. The parts from an old bell or buzzer may be used, which consist of a soft-iron armature, H, Fig. 1, having a strap of spring brass, J, attached by soldering and pivoted at K, with an adjusting screw, L, to set the tension. Another U-shaped spring-brass strip, M, constitutes the current breaker, which has an adjusting screw, N. The points of contact on the current breaker should be tipped with platinum. A piece of brass wire, O, is soldered to the diaphragm disk B and the soft-iron armature H, to connect them solidly. The tone of the horn can be adjusted with the screws L and N. The faster the armature vibrates, the higher the tone, and vice versa. The connections are the same as for an electric bell.--Contributed by James P. Lewis, Golden, Colo.

Combination Meat Saw and Knife

A very handy combination knife and meat saw can be made of an old discarded saw blade. The blade is cut on a line parallel with the toothed edge, allowing enough material to make a good-sized blade, then the straight part is ground to a knife edge and a wood handle attached at one end. The handle is made in halves, placed one on each side of the blade, and riveted together, then the projecting metal is ground off to the shape of the handle.--Contributed by A. C. Westby, Porter, Minn.

Clamp Used as a Vise

A carpenter's wood clamp fastened to the edge of a bench, as shown in the sketch, makes a good substitute for a vise for many kinds of light work. If the clamp is located over or in front of the bench post, holes must be bored in the latter to admit the ends of the clamp screws. A hole is bored through the shoulder screw and a handle attached as shown.--Contributed by H. W. J. Langletz, Harrisburg, Pa.

Wire Expansion Meter

When there is a current of electricity in an electrical conductor a certain amount of heat is generated due to the opposition or resistance of the conductor to the free passage of the electricity through it. The heat thus generated causes a change in the temperature of the conductor and as a result there will be a change in its length, it contracting with a decrease in temperature and expanding with an increase in temperature. The temperature of the conductor will change when the current in it changes, and hence its length will change, and it will reach a constant temperature or a constant length when the current in it is constant in value and the rate at which it is giving off heat is exactly equal to the rate at which heat is being generated in it.

The fact that there is an actual change in the length of the conductor due to a change in current in it constitutes the fundamental principle of the following simple instrument.

The parts needed in its construction are as follows: An old safety-razor blade; one 8-in. hatpin; two medium-size nails; a short piece of German-silver wire; a small piece of sealing wax; a 1/2-in. board for the base, approximately 3-1/2 in. by 10 in., and a small piece of thin sheet brass. Remove the head from the hatpin and fasten the blunt end in the center of the safety-razor blade A with a piece of sealing wax so that the pin B is perpendicular to the blade as shown. Now drive the two nails into the board C, so that they are about 1/4 in. from the edges and 1-1/2 in. from the end. Fasten the piece of German-silver wire D to these nails as shown. The size of this wire will depend upon the value of the current to be measured. Make a small hook, E, from a short piece of rather stiff wire and fasten it to the hatpin about 1 in. from the razor blade. The length of this hook should be such that the pointed end of the hatpin will be at the top of the scale F when there is no current in the wire, D. The scale F is made by bending the piece of sheet brass so as to form a right angle and fastening it to the base. A piece of thin cardboard can be mounted upon the surface of the vertical portion of the piece of brass and a suitable scale inked upon it. The instrument is now complete with the exception of two binding posts, not shown in the sketch, that may be mounted at convenient points on the base and connected to the ends of the German-silver wire, thus serving as terminals for the instrument.

The completed instrument can be calibrated by connecting it in series with another instrument whose calibration is known and marking the position of the pointer on the scale for different values of current.

How to Make a Fire and Burglar Alarm

A very serviceable fire and burglar alarm may be installed by anyone who can work with carpenters' tools and who has an elementary knowledge of electricity. Fire and burglar alarms are divided into two general types, called "open circuit" and "closed circuit," respectively.

In the open-circuit type of alarm all the windows, doors, and places to be protected are equipped with electrical alarm springs which are in circuit with an ordinary vibrating bell and battery, and these alarm springs are all normally open. When a window or door is disturbed or moved more than a predetermined amount, the bell circuit is closed and the alarm sounded. The arrangement of such an alarm is shown in Fig. 1. A switch, A, is placed in circuit so that the alarm may be disconnected during the day and the opening and closing of doors and windows will not operate the bell. It is best not to place a switch in the fire-alarm circuit as this circuit should be in an operating condition at all times.

The alarm switch controlled by the window consists of a narrow metal plate, B, and a spring, C, mounted in a recess cut in the side of the window frame. The spring C is bent into such a form that its upper end is forced into contact with the plate B, when the window is raised past the outwardly projecting part of the spring C, and the bell circuit is thus closed. The position of the alarm switch can be adjusted so that the window may be opened a sufficient distance to permit the necessary ventilation but not allow a burglar to enter.

The alarm switch controlled by the door is arranged in a different manner. In this case the free end of the spring D is held away from contact with the spring E by the edge of the door, which forces the spring D back into the recess cut in the door jamb. When the door is opened the spring E is permitted to move out and come into contact with the spring or plate E, and the alarm circuit is thus closed. The form of the spring D can be so adjusted that the door may be opened some distance, but not enough to allow a person to enter, before the alarm is sounded.

An alarm switch, identical with that just described for the door, should be mounted in the upper part of the window frame to take care of the upper sash. This alarm switch may be located low enough to permit the window to be lowered for the purpose of ventilation without sounding the alarm.

The wires for these various alarm switches should be run as near completely concealed as possible to prevent them being tampered with by curious parties, who may unintentionally break one of the conductors and thus make some part of the system inoperative. It might be best to test the system occasionally, to make sure all switches are in operating condition.

The fire-alarm switch consists of two springs that are held from contact with each other by means of a thin cord. This switch is placed in the location to be protected, or wherever a fire is most likely to break out, such as over the furnace, in the coal bin, etc. When the cord is destroyed the springs make contact and the alarm is sounded. A metal having a very low melting temperature may be used instead of the cord, and the alarm will be sounded when the temperature exceeds a certain amount and the actual occurrence of a fire thus prevented. In some cases, the fire-alarm switch may be completely destroyed and the alarm circuit will then be opened and the bell will cease ringing. To prevent this trouble a small electric drop may be placed in the circuit, the arrangement being similar to that shown in Fig. 2. When the shutter of the drop falls, due to the closing of the alarm circuit, there is a second circuit closed, and this second circuit remains closed until the shutter is restored to its vertical or normal position, or the switch, A, is thrown to the open point. The addition of the drop in the burglar-alarm circuit may prove to be an advantage, as a burglar cannot stop the alarm, after he has once closed any of the alarm switches and operated the drop, by simply restoring the window or door to its original position.

In the closed-circuit type, the alarm switches are all normally closed and the alarm is sounded by opening the circuit at some point. The arrangement of such an alarm is shown in Fig. 3. The alarm switches are all connected in series in this case and in circuit with a closed-circuit battery and relay or drop. The drop or relay controls a local circuit composed of an open-circuit battery and an ordinary vibrating bell.

The operation of a drop on a closed circuit is a little different from its operation on a normally open circuit. The drop for the closed circuit must be so constructed that its latch holds the shutter in a vertical position when there is a current in the drop winding, but allows it to fall as soon as the drop circuit is opened.

An ordinary telegraph relay may be used in connection with the closed-circuit alarm. The connections to the relay are such that the bell circuit is normally open and remains so until the armature of the relay is released, which does not occur until the circuit of which its winding is a part is opened at one of the alarm springs. A special switch, A, and resistance, B, are shown connected in circuit in Fig. 3, the object of which is as follows: When it is desired to disconnect the alarm springs or make them inoperative they must be replaced by another circuit which will permit a sufficient current to pass through the relay winding at all times, to prevent its armature from being released and sounding the alarm. The switch A is so constructed that either the alarm switches or the resistance B is in series with the battery and relay winding at all times, there being no open-circuit position for the switch.

The fire-alarm switch for this type of signal may be made from a narrow piece of tin foil, or some metal having a low melting temperature, mounted between two insulated clips that are connected in the alarm circuit.

Strips of gold or silver foil may be placed on windows and connected in the alarm circuit, which will give a protection from theft by breaking the glass.

Two or three gravity cells will serve very nicely for the closed-circuit battery, while several dry cells will do for the open-circuit or bell battery.

All types of alarm switches can be purchased at any up-to-date electrical supply house, but their construction and operation is so simple that they may be easily made by almost anyone. A detailed description of the construction of the various parts of the above circuits will not be given here, but such details can be safely left to the ingenuity of the person installing the system.

It is easily seen from the above description that a burglar who might discover that a house was wired for alarm would be greatly perplexed to know what to do, for the very thing that would prevent one kind of alarm from ringing would cause the other to ring.

Removing a Rear Bicycle Sprocket

If a bicycle rider desires to remove the rear sprocket for changing the gear, or for any other reason, and there is no large pipe wrench at hand, a piece of tube or pipe, as shown in the sketch, can be used as a lever. Fasten one end of the chain in one end of the pipe with a wedge and place the other end of the pipe on a sprocket. The chain is then placed over the sprockets and a leverage equal to any pipe wrench is secured.--Contributed by Jno. V. Loeffler, Evansville, Ind.

Hand Propeller-Wheel Attachment for a Rowboat

The rear fork of an old bicycle frame, with the crank hanger attached, and the rear hub constitute the main parts of the propelling device. One of the cranks is cut from the hanger and a bracket attached to the frame, as shown, for making it fast to the stern of the boat. Two propeller blades are bolted to the rear hub. A rudder is fastened to the rear tube of the frame with hooks and eyes so that it can be turned with a handle at the top, or with ropes run to a wheel. The illustration shows the connection of the device to a boat.--Contributed by Berge Lion, Fresno, Cal.

An Attached Back for a Photographic Printing Frame

In using the ordinary photographic printing frame with a spring-pressure back, the back must be entirely removed from the frame to put in the paper, and as this operation is carried on in a dim light, the back is often mislaid, causing no little inconvenience and delay. To do away with this annoyance, I placed at one end of the frame, as shown in the sketch, a second hinge made of cloth or any pliable material. When the pressure springs are released, the back swings down on this auxiliary hinge, and after changing the papers, it is instantly closed by a slight movement of the hand, making it very rapid and easy to use.--Contributed by Thos. L. Parker, Wibaux, Mont.

Repairing a Worn Stop Cock

The plug of a worn stop cock, or one that has been reground, of the type shown in the illustration will project beyond the bottom so that the ring, or washer, and screw will not draw it tightly into place.

To remedy this trouble, file off a portion of the plug on the line AA and also file off a sufficient amount of the screw on the line BB. When the plug is replaced and the washer and screw drawn up, the stop cock will be as good as a new one.--Contributed by James M. Kane, Doylestown, Pa.

Tool Holders Made of Brass Clips

Hangers to grip tool handles can be easily formed of sheet metal in any desired material. The clips are shaped as shown at A in the sketch. Any number of the clips may be fastened with screws to a wood crosspiece or a wall in such a manner as to make openings into which the handles of the tools are pressed. Before fastening the clips they should be spaced for the widths of the handles.--Contributed by F. H. Tillotson, Sycamore, Ill.

Removing Perspiration Stains from Delicate Cloth

Lay the stain in the cloth over some blotting paper, and sponge the cloth with a grain-alcohol and ether solution, which should be made by mixing equal portions of each. The sponging should be quite vigorous and kept up until the cloth is dry, then the spot should be touched lightly with ammonia water, which can be purchased at any drug store. This will leave a slight blur, which can be removed by rubbing with French chalk on the wrong side. The chalk is cheap and can be procured with the ammonia water. Do not forget the blotting paper, as it keeps the solution from forming a ring around the spot.

Buttonhole Cutter

If the buttonhole scissors are mislaid or there are none at hand, the holes may be cut in the manner shown in the sketch. Place a piece of wood, having a width equal to the length of the buttonhole, on the table and lay the cloth over it in the line where the holes are required, then draw a sharp knife across the cloth on the wood where the holes are marked. This will cut the cloth neatly and accurately.--Contributed by A. S. Thomas, Gordon, Can.

Filing Small Rods in a Lathe

Reducing the diameter of a small rod by filing while it is turning in a lathe is a difficult thing to do, as the pressure of the file on one side bends the rod. The filing may be easily accomplished by using two files, as shown in the sketch. In this manner almost any amount of pressure can be applied by squeezing the files together without danger of bending the rod.--Contributed by J.F. Tholl, Detroit, Mich.

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Young sleepwalkers may be cured if watched and given a good switching until they are wide awake.

A D'Arsonval Galvanometer

A galvanometer in which the moving part of the instrument is a permanent magnet controlled by the action of the earth's magnetic field and the magnetic effect of a current in a coil of wire, that usually surrounds the magnet, has the great disadvantage of having its indications changed, although the current itself may remain constant, due to a change in the strength of the magnetic field in which the instrument operates. The operation of instruments of the above type is satisfactory only in localities where there is a practically constant magnetic field for them to operate in, which it is almost impossible to have, due to the presence of permanent and electric magnets and magnetic materials such as iron and steel.

An instrument constructed as follows will not have the above disadvantage and its operation will be a great deal more satisfactory, as its indications will be practically independent of outside disturbances. In this instrument, the moving part is the coil carrying the current, and it moves in a permanent magnetic field so strong that other disturbing magnetic effects can be neglected. The coil is hung by means of a fine wire and the twist in this wire is the only force acting to bring the coil back to its zero position, after it has been deflected, and maintain it there.

The construction of the magnet and containing case for the instrument will be taken up first. Obtain a piece of Norway iron, 1/2 in. square and about 9 in. long. Bend this piece into the form shown in Fig. 1, and file off the inner edges until they are parallel and about 7/8 in. apart. Drill four 1/8-in. holes in the ends of this piece, two in each end, as indicated. This piece of iron is first tempered and then magnetized by placing it in contact with a powerful electromagnet. Cut a second piece from some soft iron with dimensions corresponding to those given in Fig. 2. Drill two 1/8-in. holes, A and B, in this piece as shown in the sketch. This second piece is mounted between the poles of the magnet, as follows: Cut from some 1/32-in. sheet brass a piece similar to the one shown in Fig. 3. Drill the holes indicated and thread those designated by A, B, C, D, E, and F to take a 1/8-in. machine screw. Bend the upper end of the piece over at the point indicated by the dotted line until it is perpendicular to the lower part. The center of the hole in the projecting part K, when it is bent over, should be about 1/4 in. from the outer surface of the main part of the piece. The small piece of iron is then fastened to the piece of brass with two round-headed screws that pass through the two holes in it and into the holes A and B in the brass piece. The magnet is mounted, also with small brass screws, so that the main part of the magnet and the piece of brass extend in opposite directions, as shown in Fig. 1. The assembled parts are then mounted on a wooden board, whose dimensions are given in Fig. 1, with three brass screws that pass through the holes G, H, and J, as shown.

The moving coil of the galvanometer is constructed as follows: Cut from some 1/8-in. pine a piece 1-1/8 in. long and 5/8 in. wide. Cut two other pieces whose dimensions, except their thickness, are 1/4 in. larger than the first piece. Then fasten these two pieces to the sides of the first, with three or four small screws through each of them, thus forming a small spool. Saw about 16 slots with a very fine saw in the edges of the projecting pieces and a short way into the edge of the center piece. Wind on this spool about 300 turns of No. 38 gauge silk-covered copper wire. Start with the terminal of the wire in the center of one end of the spool, with a few inches of free wire for making connections, and end up with the terminal in the center of the opposite end of the spool. A small thread is then passed through the slots under the coil and tied, thus serving to hold the various turns of wire together when the coil is removed from the form. The coil should be given a coat of shellac as soon as it is removed from the form.

Two pieces must now be attached to the top and bottom of the coil to be used in making electrical connections and suspending the coil. Cut from some very thin sheet brass two pieces whose dimensions correspond to those given in Figs. 4 and 5. Drill a small hole in the center of each of these pieces. Bend the lower part of each piece over at the dotted lines L until it is perpendicular to the main portion of the piece. The bent-over portions of these two pieces are then fastened to the ends of the coil with some fine thread, making sure that they are in the center of the ends before they are fastened. The terminals of the coil are now soldered to these pieces. It would be best to place a sheet or two of thin paper between the brass pieces and the coil, to prevent any part of the coil, except the ends, from coming into contact with the brass pieces. Obtain a small piece of thin mirror and mount it with some glue, as shown by the dotted lines in Fig. 4.

The upper support for the suspension is shown in Fig. 6 and consists of a 1/8-in. threaded screw, A, that passes through the hole in the part K, Fig. 3, and is provided with two lock nuts, B. The lower end of this screw should be slotted a short distance, and a small screw put through it, perpendicular to the slot, so that a wire can be easily clamped in the slot by turning up the screw. Next, take a piece of 1/32-in. brass, as shown in Fig. 7, and bend it at the dotted line A until it forms a right angle. The hole B should be threaded to take a 1/8-in. screw. The holes C and D are for mounting the piece on the back of the instrument. Slot the end of a 1/8-in. screw, about 1/2 in. long, and put a screw through the end as for the upper support for the suspension. This piece is mounted below the position the coil is to occupy, as shown by M, Fig. 1.

A case should be made for the galvanometer whose inside dimensions correspond to those of the piece N, Fig. 1, and whose depth is about 3/4 in. more than the thickness of that piece. Four pieces of wood can be fastened in the corners that will allow the case to slip just far enough on the piece N to make the edge of the case and the back surface of the piece N flush. Cut an opening in the front of this case, about 2 in. long and 1 in. wide, in such a place that the center of the opening is about level with the ends of the magnet. Fasten, back of this opening, a piece of thin glass with four small screws whose heads rest upon the edge of the glass. The interior of this case and all the parts should be given a coat of lampblack mixed with a little vinegar. Two small binding posts, O and P, are mounted on the upper end of the piece N and connected to the upper and lower supports for the suspension of the coil.

This galvanometer will work best, of course, when it is in an exactly vertical position and the following simple device, when attached to it, will allow it to assume this position independent of the level of the surface its base may rest upon. Cut from some 1-1/8-in. brass two pieces, 1/2 in. wide and 2-1/2 in. long. Drill a 1/8-in. hole in the center of each end of them, 1/4 in. from the end, and a 1/4-in. hole through the center of each. Bend these pieces to a 3/4-in. radius. Cut from some 1/2-in. hard wood a block, 1-1/4 in. square. Fasten the two pieces of brass to the wooden block with 1/8-in. screws, as shown in Fig. 8. One of these pieces is fastened to the upper end of the piece N, Fig. 1, so that the galvanometer will hang vertically. The other piece is fastened to a bracket from which the galvanometer is suspended. A suitable bracket for this purpose can be easily made. When the galvanometer is hung in this way, two binding posts are mounted on the bracket, and connected to the two on the galvanometer. In this way the galvanometer will not be disturbed when making connections.

The suspension is made as follows: Take a piece of small copper wire and roll it out flat. Solder one end of a piece of this wire in the hole in the piece of brass, with the mirror mounted on it. Fasten a piece of the same wire to the lower brass piece, attached to the coil. The upper piece of wire is then clamped in the end of the screw A, Fig. 6, so that the coil hangs perfectly free about the iron core. The lower piece of wire is bent around a small rod several times and its end fastened in the slot in the lower screw.

The deflection of the instrument is read by causing a beam of light from a lamp or candle to be reflected from the mirror to a scale located in front of the instrument. If the light from the lamp is allowed to shine through a small slit in a piece of dark paper, there will be a streak of light reflected upon the scale, instead of a spot.

To use this instrument in measuring larger currents than it will safely carry, connect it in parallel with another resistance which will carry the larger part of the total current. The galvanometer can be calibrated with this resistance, which is known as a shunt.

How to Make Advertising Lantern Slides

Procure some old discarded photographic films and remove the gelatin coating by soaking them in hot water. When dry, write the desired words on the thin celluloid and place it between two pieces of glass, lantern-slide size, and bind them as in making a lantern slide.

With the use of a carbon paper a very nice slide can be made by writing the words on a typewriter, and it will serve the purpose of an expensive announcement slide.--Contributed by F. P. Dickover, Atkinson, Neb.

Utilizing Old Brush Handles

The handle cut from an old dusting brush, fitted with the brass end of a shotgun shell, makes a first-class tool handle. The handle is cut off at A and the wood cut down to fit tightly into the brass shell.--Contributed by James M. Kane, Doylestown, Pa.

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Tincture-of-iodine stains may be removed from clothing or the skin by using strong ammonia water.

Preserving Paints and Pastes

White lead, thick shellac, and pastes that are used occasionally may be preserved by laying a piece of leather over the exposed surface. When these materials are kept in cans, cut a piece of leather from the upper of a heavy boot of such a size that it will drop freely into the container. Form a handle on the leather disk by driving a nail through its center from the under side. Press the disk down smoothly over the surface of the contents and a thin film of oil will soon form over the disk, effectually excluding the air. A loose cover is placed over the container, to keep out dust.--Contributed by Luther McKnight, Colorado City, Col.

A Burner for Soldering Small Work

As it was necessary for me to solder the joints of fine wires on electrical instruments, and other small work, I found myself in need of a blowpipe that gave a small but very hot and easily directed flame, was automatic in its operation and required no blast. I tried an ordinary acetylene burner on coal or city gas, and found it gave an intensely hot, nonluminous flame, due to the forced draft of air through the small holes. This flame will melt silver, copper and, also, silver solder. Its great advantage lies in the fact that it may be used for sweating together small articles rapidly and with great neatness. I always keep this blowpipe burning, as the gas it consumes is very small, and the burner is kept within easy reach by using a hanger, as shown in the illustration.

A single jet of flame is obtained by stopping up one of the tips, which is very useful in many ways. This flame may contain a small luminous spot on some city gas, but it does not interfere with the heat.--Contributed by Arthur Worischek, New York City.

A Safety-Match-Box Holder

A holder, as well as a tray, for safety matches can be made from any ordinary tobacco can. The metal on one side is cut as shown and the pieces bent up to form standards for holding the match box in an upright position. The openings left where the metal was raised are used for dropping the burned matches into the box. The hinged cover is used for emptying the tray.--Contributed by David B. Lutz, E. St. Louis, Ill.

Removing Ink Stains from Book Leaves

When the leaves of a book are accidentally stained with ink it can be removed quite readily by the following process: After removing as much of the ink as possible with a camel's-hair brush dipped in water, soak the stained parts in a solution of oxalate of potash, or better still, oxalic acid. This will remove all the ink. Treat again with water, as before, so that when it dries out no salt will appear on the paper. This process does not affect printer's ink.--Contributed by S. G. Thompson, Owensboro, Ky.

A Needle-Spray Nozzle

To make a needle-spray nozzle, either insert a 22-caliber cartridge in a small tube, or place a 45-caliber shell over the end of the tube and solder it in place. The end is perforated to make one or more small holes, as desired.

How to Make an Electrotype Stamp

The method described in the following produces a very good metal stamp for any name, initial, drawing, etc.

Procure a smooth and perfectly level sheet of brass about 1/16 in. thick and about 3 by 4 in. in size. Nickelplate the brass so that the copper deposit will not stick to it. If a small plating outfit is not at hand the piece may be plated at a local plating works for a nominal price. Dip the plate in melted paraffin until the coating is about 1/16 in. thick and see that no metal is exposed. Drill a hole in one corner and attach a wire.

Draw the letters or sketch desired, using a metal stylus having a sharp point, taking care to make the lines scratched in the wax clean and open to the surface of the metal (Fig. 1).

A large open-mouthed bottle or glass tank will be required for the plating solution, which is made by dissolving copper sulphate in water until the solution is saturated with the sulphate and then adding a few drops of sulphuric acid. Immerse the plate in the solution as shown in Fig. 2 and connect with the zinc pole of the battery. Put a piece of pure copper in on the opposite side of the jar and connect with the carbon pole of the battery, using care in each case to keep the connection of the wire and the upper part of the plate above the surface. One or two dry cells will be sufficient. If the current is right, the deposit on the waxed plate will be a flesh pink; if too strong, it will be a dirty brick color and the plate will have to be washed and the current reduced. When the desired thickness of metal is deposited, remove the plate and pour boiling water on the back. This will remove the thin copper shell and the nickeled plate may be laid away for future use.

Procure a flat pan and after placing the shell in it, face down, sprinkle a little resin or soldering flux on the back. Lay three or four sheets of the lead from tea packages on the back of the shell and heat it over a spirit lamp or on the stove until the lead melts and runs into the crevices on the back of the copper, thus making it solid and suitable for mounting. Mount as shown in Fig. 3 with small brass screws and after polishing the surface to remove dirt, etc., the stamp is ready for use.

An ordinary stamp pad will do for inking, but the best ink to use is printer's slightly thinned, as the ordinary rubber stamp ink is not suitable for a metal stamp.--Contributed by S. V. Cooke, Hamilton, Ont.

A Cover for a Bottle

If a glass medicine bottle is to be carried constantly in the pocket, it is best to cover it with leather or rubber. The sketch shows how to cut the pattern so that it will fit a square bottle. The bottle is placed on the leather, or a piece of paper as a pattern, and the outlines marked upon it. The leather or paper is then folded over four times and cut out as shown. This cover will prevent the glass from being scattered in the pocket should the bottle be accidentally broken. It always provides a means of distinguishing it from other bottles of the same type and size.--Contributed by James M. Kane, Doylestown, Pa.

Boring a Long Hole

The usual method of boring a hole through a piece of wood longer than the bit is to bore from each end. To make the hole straight by this method, split the wood or saw it in halves, then make a knife kerf in both pieces on a center line of the hole and glue the pieces together. The spur of the bit will follow the kerf from either end, and the result will be a meeting of the holes, almost perfectly in the center.--Contributed by Ernest J. Dickert, Niagara Falls, N. Y.

Covering for a Gas-Stove Top

While frying or cooking on a gas stove the grease will spatter over the top and make the cleaning rather difficult, especially where there are many crevices. A simple method of avoiding this trouble is to place a paper over the top of the stove, with round holes cut out for each burner a little larger than the pots and pans used in the cooking. This will keep the stove very clean with a minimum of bother. A paper cut to fit the under pan will keep that part clean.--Contributed by S. F. Warner, East Orange, N. J.

Homemade Skis

Not having a bent board suitable for a pair of skis, I proceeded to make the skis in the following manner: A cheese box was procured and two pieces cut out of the side, each 15 in. long and 3 in. wide. These were used for the upturned ends and two boards, 6 ft. long and 3 in. wide, served as the runners. A notch, 4 in. long and 1/8 in. deep, was cut in one end of each board to receive one end of the thin curved pieces cut from the cheese box, which were fastened with screws. The upper end of each thin piece was cut to a point.

A piece for the foot, 10 in. long and 3 in. wide, with a notch 1 in. wide and 1/4 in. deep, was fastened in the center of the runner. A strap is run through the notch for holding the ski to the foot--Contributed by Henry Meuse, Reading, Mass.

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To remove iron rust or ink stains from cloth, use a warm solution of oxalic acid with a few crystals of citric acid added. Repeat the washings until the stain is removed.

How to Make a Dry Cell

The containing vessel for the cell should be made from sheet zinc. It should be cylindrical in form, approximately 2-1/2 in. in diameter and 6 in. long. This vessel is to form the negative terminal of the cell and a suitable connecting device, similar to the one shown in the sketch, should be provided and securely fastened to the upper edge of the vessel. The vessel should be lined with some heavy blotting paper, both sides and bottom.

Place into a glass jar a small quantity of chloride-of-zinc crystals, and pour over them 1/2 pt. of distilled water. Allow the crystals to dissolve at least one-half hour. If the crystals all dissolve, add more until some remain in the bottom of the jar, or until the liquid is saturated. Pour off the solution and dilute it by adding an equal part of distilled water. Add to this solution sal ammoniac, in the proportion of 1 lb. of sal ammoniac to every 2 qt. of liquid. Fill the dry-cell vessel with this solution and allow it to remain until the blotting paper is completely saturated.

Obtain a good size electric-light carbon, about 5/8 in. in diameter, and file one end down as shown. Drill a hole through the carbon and mount a terminal.

Make a mixture of equal parts of finely powdered carbon and manganese dioxide of sufficient amount to almost fill the vessel. Add to this mixture some of the solution and thoroughly mix them. Continue adding solution until a thick paste is formed.

Pour the solution out of the vessel and allow the latter to drain for a few minutes in an inverted position. Place the carbon rod in the center of the vessel and pack the paste down around it, being careful not to move the carbon rod from its central position. The vessel should be filled with the paste to within about 5/8 in. of the top. The lower end of the carbon rod should not be nearer the bottom of the vessel than 1/2 in. Over the top of the paste place a mixture of equal parts sand and fine sawdust and then, over this, a layer of pitch, which acts as a seal for the cell. A layer of blotting paper should be placed between the sand-sawdust mixture and the carbon-manganese mixture. The side lining of the vessel should be turned in before the sand-sawdust mixture is placed in the top of the cell. The outside of the cell should be covered with some heavy pasteboard, which will serve to insulate the negative terminal from the surface upon which the cell rests.

A Hose-Nozzle Handle

A handle for a garden-hose nozzle is easily made of a piece of wire and the wooden part of a package carrier. The wire is bent to receive the hose at A, and, after the handle is slipped on, the other end is formed to fit tightly over the brass nozzle at B. The hose nozzle can be easily carried with the handle, which will keep the hand dry.--Contributed by F. G. Marbach, Cleveland, O.

Guide for Cutting Mortises

After spending considerable time in cutting one mortise in a piece to make the settee described in a recent issue of Popular Mechanics Magazine, I devised the plan shown in the sketch which enabled me to cut all the mortises required in the time that I cut one in the ordinary manner. Two metal plates, one of which is shown in the sketch, having a perfectly straight edge, are clamped on the piece with the straight edge on the line of the mortise. A hacksaw is applied through holes bored at the ends and a cut sawed along against the metal edges.--Contributed by George Gluck, Pittsburgh, Pennsylvania.

Insect-Proof Poultry Roost

To protect the poultry from mites and other insects while roosting, I constructed a roost hanger, as shown, with oil cups made of empty shoe-polish cans. The cover of the box was nailed to the roost and the bottom, for holding the oil, on top of the roost support. A large nail was driven through the support from the under side and through the center of the can bottom, so that about 1-1/4 in. projected above the latter.

The can cover was perforated in the center and a hole, about 1/2 in. deep, was drilled in the roost so that the end of the nail would easily slip into it. The bottom of the can was filled with a mixture of kerosene, vaseline and carbolic acid and the roost set in place. Both ends of each roost are fixed in the same way. This makes it impossible for any insects to get on the roost.--Contributed by Rudolph Netzeband, St. Louis, Mo.

To Prevent Shade Rollers from Unwinding

Obtain a stick for the hem on the lower end of the shade that is 2 in. longer than the shade is wide. Place two small wood screws in the window casing below the shade roller in such a position that they will catch the ends of the stick when the shade is raised to the top.--Contributed by Harry E. Kay, Ossining, N. Y.

A Screen and Storm-Door Cushion

A good cushion that will prevent a spring door from slamming can be made out of material cut from an old rubber boot or, better still, from an old hollow rubber ball. Three strips of heavy rubber, 1-1/4 in. long and 3/8 in. wide, are cut and each fastened with two tacks so that the center will make a hump, as shown in the sketch. One cushion is fastened near the top, one near the bottom, and one in the center, in the rabbet of the door frame.--Contributed by D. Andrew McComb, Toledo, O.

Repairing a Coaster Brake

Anyone having a bicycle coaster brake that is apparently useless because it will not brake, can easily repair it in the following manner: Remove the inner hub by unscrewing the cones and insert a piece of clock spring, about the same width as the brake shell and almost as long as its inside periphery. Replace the parts and the repair will render the brake quite as efficient as a new one. The spring serves as a braking surface for the expanding steel shoes of the brake.--Contributed by Heber H. Clewett, Pomona, Cal.

Flypaper Holder

The ordinary method of using sticky flypaper is quite annoying, as it cannot be easily removed from anything that may come in contact with its sticky surface. The best way to avoid this trouble is to make a holder for the paper, and one can be constructed of a piece of wire and a metal cover taken from a jelly glass. The wire is threaded at one end on which the cover is clamped between two nuts. The upper end of the wire is shaped into a hook for hanging it wherever desired. The paper is rolled with the sticky side out and tied with strings, then slipped over the wire and set into the inverted cover. The cover prevents any of the sticky substance from dripping onto the floor and the wire holds it from being blown about the room.--Contributed by Percy de Romtra, Cape May Point, N. J.

A Fish Rake

The fish rake can be made in any size, for minnows or salmon, but it is especially adapted for fish that run in schools, like smelt, herring and minnows. Procure a piece of wood, 7 ft. long, 4 in. wide and 7/8 in. thick, and make a handle 3 ft. long on one end. Dress the other end to an edge, rip off a 1-in. strip and drill holes to receive nails or pieces of wire from the back, through the edge, and projecting about 4 in. The strip is then replaced and fastened with screws. The handle can be cut from the blade and jointed by using tubing. This makes it handy to take apart and pack.--Contributed by L. W. Pedrose, Seattle, Wash.

To Harden Small Blocks of Wood

Small blocks of wood can be hardened so that they will not split so easily when small screws are inserted by boiling them in olive oil for about 10 minutes. The olive oil can be kept for future use. If it is desired to waterproof the blocks after hardening them, they should be placed in melted paraffin and allowed to cool in the solution. This gives the block of wood a good appearance and makes it nonabrasive and waterproof.

Homemade Clothesline Reel

It is much better to make a small reel, like the one shown, for a clothesline than to wind the line on the arm, the usual method of getting it into shape for putting away.

The reel consists of two strips of wood, 16 in. long, 3 in. wide and 7/8 in. thick. These are joined together with two pieces of broom handle, allowing a space of 9 in. between the sides and an extending handle of 5 in. on opposite sides, as shown.--Contributed by Bert Longabaugh, Davenport, Iowa.

Gear-Cutting Machine

Perhaps the last thing that would be thought within range of the amateur who lacks a full equipment of machinery is the cutting of gear wheels. The device shown in the sketch is very practical, and, with the most ordinary assortment of iron-working tools, will serve to turn out an accurate gear.

No system of supports is shown, as they are easily supplied. A flat, square board, B, as large as can be obtained--2 ft. on a side being the safest minimum--is used for a dial. A sheet of paper is pasted over the entire board and a large circle drawn on it. This circle is divided into as many parts as there are to be teeth in the gear. A depression is made with a prick punch at each division. A shaft, C, is run through the center, to which an arm, A, is firmly attached. A nail, N, is placed at the end of the arm so that the point can enter each of the punch marks on the periphery or circumference of the circle. A blank wheel, W, is attached to the shaft C, in the position shown, and resting on the iron plate or strap F. A cutting tool, D, works up and down in a slot in F. This cutter is held away from the blank wheel by the spring S, and moved up to it by the screw G, acting through the sliding member H. A stove bolt may be used for G, with the nut firmly fastened to the strap F. The cutter is actuated with a handle E, whose motion is limited by the pegs as shown. In Fig. 2 is shown a top view of the strap E, with a cross section of the cutter and the slot in which it works.

The operation of the mechanism is as follows: With the blank wheel in place set the nail N in one of the punch marks and move the handle E downward. This will make a slight cut on the wheel. Then give the screw G a turn or two, which will make the cutter take a deeper bite, and push the handle down again. This operation is repeated, screwing G constantly deeper, until it is stopped by the locknut J, which regulates the depth of the cut. Move the nail N to the next punch mark and repeat. The operations are very quickly performed and the circle will be closed almost before you know it.

There are several points to be observed. The accuracy depends upon three things. First, the slot through which the cutter passes must be tight-fitting, even at the expense of working hard. Second, the shaft C must fit tightly in the holes made for it through B and F, also the arm A must be firmly attached, the shaft being filed flat at the point of attachment. The blank wheel should be keyed on the shaft or securely fastened with a setscrew. Third, the nail N must enter the punch marks accurately. As the grinding circle is so much larger than the blank, any error here is greatly reduced in the finished wheel. Once in a punch mark the nail must not be allowed to slip until the tooth has been cut.

In practice, it will be found better, after each stroke of the handle, to give a quarter turn outward to the screw G, thus avoiding the scraping of the tool on the up stroke. The cutter can be made of any suitable steel with the cutting point ground to give whatever shape is desired for the tooth. The best shape for any particular purpose can be found by reference to a book on gears.

This cutter is adapted, of course, only to the softer metals. For experimental purposes a blank cast in type metal is excellent and will last as long probably as required. The mechanism here described will cut brass perfectly well and a gear made of this more durable metal will answer for a finished construction. Type-metal blanks commend themselves because they are so easily cast, any flame which will melt solder being sufficient, and the molds, of wood, plaster of Paris or any easily worked material, being quickly constructed.--Contributed by C. W. Nieman, New York City.

A Potato Peeler

The guard is made of a piece of wire about 1 in. shorter than the blade of an ordinary table knife. The ends of the wire are turned into a coil to resemble a coil spring with coils close together. Allow enough wire to project on one end to be flattened and pointed for an eye extractor.

When this device is placed on the knife, the contrivance works on the same principle as a spokeshave. The first setting peels the potato without any appreciable waste, the other setting may be as desired for cutting slices.--Contributed by H. W. Ravens, Seattle, Washington.

An Easy Way to Develop Roll Film

This is simply a different motion to the tiresome seesaw one usually employs when films are being developed. In wetting them down previous to immersion in the developer, do not keep them in the water long enough to become limp, but remove them after a few quick dips, says Camera Craft, They will then retain some of their curling tendency, so that by taking one end in one hand and gradually lowering the film into the dish of developer and then raising it out of the dish, it will be found that the film will roll and unroll quite readily, much as one would let out or wind in a reel. This method will result in quicker development, because the roll is nearly always immersed in developer. The method necessitates using only one hand, making it possible to develop a second strip at the same time with the other. The illustration shows quite clearly just how the film will behave.

A Shoe Hanger

An inexpensive shoe hanger can be made of a strip of tin, about 1/2 in. wide and as long as the space will permit. Cut notches along one edge and bend the tin and tack or screw it on a strip of board or to the inside of the closet door. The shoes are hung up by the heels with the toes down.--Contributed by C. R. Poole, Los Angeles, Cal.

How to Make a Small Vertical Drill

A small hand drill with a three-jaw chuck that will take the smallest drill can be purchased very reasonably. For ordinary work these drills do very well, but for comparatively deep holes, or when using long, slender drills, some sort of a stand should be made, if for no other reason, to avoid breaking the drills, which is almost invariably due to the side motion of the hand. There are other reasons, however, for making such a stand, and these lie in the fact that it is impossible to drill by hand at right angles with the surface of the metal, or to hold such a drill sufficiently steady to avoid widening the hole around the top.

As each make of hand drill will require a somewhat different form of stand, no detailed description need be given of the one illustrated. The principal point is to have the base and standard securely set at right angles to each other, and then provide a smoothly sliding piece to which the hand drill may be clamped. The edges on this slide and the corresponding guides should be planed off to an angle of 45 deg. One of the guides should be adjustable, which may be arranged by elongating the screw holes and placing small washers under the heads of the screws that hold this guide to the main standard.

A neat little hand drill, arranged in this manner and firmly secured to the bench, may also be used for finishing the ends of small shafts, either flat or pointed, for polishing screw heads, etc., to all of which it gives that workmanlike appearance that can only be had when things are polished with a true rotary motion.--Contributed by John D. Adams, Phoenix, Ariz.

Decorating Candles

Candles can be easily decorated by the following method: The designs can be selected from paper prints which are tightly wrapped around the candle with the design in contact with the wax. Strike a match and play the flame over the back of the paper. Allow time enough for the melted wax to harden and then remove the paper. The print will be transferred to the wax.

Select designs that are not larger than the circumference of the candle. A good impression of ink on thin paper works best.--Contributed by J. J. Kolar, Maywood, Ill.

Homemade Hacksaw Frame

A home workshop not having a complete set of tools may be supplied in many ways with tools made by the owner. The hacksaw frame illustrated is one of these. The frame is made of hard wood. The saw end is inserted in a slot sawed in the handle end, and a screw or small bolt holds it in place. The other end is equipped with a bolt having a sheet-metal head, as shown at A. The blade is kept from turning by a projection of the sheet metal which fits in a saw cut made in the frame.--Contributed by W. A. Henry, Galesburg, Ill.

Drill Press on an Ordinary Brace

As the greater part of the energy required for drilling metal by hand is used for feeding the drill, I made what I term a drill box in which the brace is held perfectly true and pressure is applied by a weight. The feed can be changed for the different metals and sizes of drills, also for drilling the hard outside of castings and relieving the drill for the softer body. The constant feed will cause the drill to turn out a long chip, and a number of holes may be drilled to a uniform depth by using the same feed and counting the turns of the brace handle.

To build the box, first find the dimensions of the brace, as shown in Fig. 1: the diameter of the head A, the clearance B from the top of the head to 1/4 in. above the top of the handle C, and the over-all length D when the longest drill is in the brace. Make a box having an inside length equal to the dimension D, plus whatever additional height may be necessary for the work. Make the inside width twice the distance C, plus 6 in. for clearance; and the inside depth the length C, plus one-half of the dimension A, plus 3 in. Use material 7/8 in. thick and nail the parts together to form a rectangular frame. Cut a piece of broomstick as long as the dimension B, and two pieces of wood as long as the inside width of the box and as wide as the dimension B. Cut two pieces 1/16 in. longer than the dimension A and as wide as the length B. Nail these latter pieces together as shown in Fig. 2, leaving a square space in the center. This frame is to be nailed inside of the top of the box flush with the front, but before doing so lay it on top of the box to determine where the center of the square space will come, and bore a hole, large enough for the round stick cut from the broom handle to slip through easily, then nail the frame on the under side of the top piece.

Procure a tough piece of wood, 1-1/2 in. square and long enough to project 2 in. over the right and 10 in. over the left side of the box top, and when in this position, locate the hole bored for the round stick and bore a hole in the square stick, 1/8 in. deep, to coincide with it. Place the head of the brace in the guide and push it up until it touches the top of the box and block it up in this position, then drop the round stick through the hole and rest it on the head of the brace. Place the socket in the lever over the top of the round stick. Make a loop, 8 in. long, of heavy wire and hang it over the right end of the lever and mark the box at the lower end of the loop. Turn in a large screw 1/2 in. below this mark allowing it to project enough to hook the loop under it. Remove the round stick and put a screw at the point the bottom of the loop reaches when the lever is flat on the top of the box. Another screw turned in between these two will be sufficient to hold the lever in position. Different-sized weights, of from 5 to 10 lb., are used on the lever, but for small drills the weight of the brace alone is sufficient.--Contributed by Maurice Coleman, W. Roxbury, Mass.

Homemade Picture-Frame Miter Box

Any person wishing to make a picture frame, or to cut down an old one, requires a miter box for that purpose, so that the molding may be properly held while sawing it, and also for nailing the corners together. I made a miter box, as shown, and found it to be just the thing for this purpose. It is built on a base similar to an overturned box, the saw guides being held on the ends of a piece, constructed as shown at A. Holes are cut in the top, as shown at B, for one of the guides and for the two wedges. Two pieces, C, are fastened with their outer edges at perfectly right angles on the top.

The frame parts are clamped against the pieces on top with the wedges driven in between the frame parts and the brackets DD. After cutting the frame parts they are tightly held in place while fastening them, in any manner desired.--Contributed by A. S. Thomas, Amherstburg, Can.

Tank-Development Methods Used in Tray Development

If there are a number of plates to be developed, place a rubber band, about 1/8 in. wide, around the ends of each plate and put them together in a tray. The bands keep the plates apart. The developer is made up as for a tank and poured over the plates, then another tray, or dark covering, is placed over the top. Allow this to stand, rocking the tray from time to time, the same length of time as is required for tank development.--Contributed by Earl R. Hastings, Corinth, Vermont.

A Pushmobile Racer for Ice

The pushmobile shown in the illustration takes the place of the one with rollers that is now so popular with the boys. The materials required, usually found about any home, consist of a foot board, 1 in. thick, 2-1/2 in. wide and 2 ft. long; two pieces of wood, each 3/4 in. thick, 2-1/2 in. wide and 9 in. long; one steering post, 1 in. thick, 1-1/2 in. wide and 30 in. long; one handle, 6 in. long; one small hinge; one carriage bolt, 1/2 in. in diameter and 2-1/2 in. long; two 1/2-in. washers; a few screws, and a pair of discarded ice skates.

One of the 3/4-in. thick pieces is fastened solidly to one end of the foot board with the ends flush. The other piece is swiveled with the bolt at the opposite or front end of the foot board so that at least one-half of the piece projects beyond the end. The steering post is hinged to the projecting end. The skates are fastened to the 3/4-in. pieces for runners. The manner of propelling the racer is the same as for the pushmobile.--Contributed by W. E. Crane, Cleveland, O.

Homemade Ellipsograph By Chelsea Curtis Fraser

An efficient ellipsograph is the only device that will make true ellipses of various sizes quickly, and such a machine is in demand on some classes of work in a drafting room. Its cost, however, is prohibitive where only few ellipses are to be drawn, but a person handy with tools can make an apparatus that will do the work as well as the most expensive instrument.

The completed ellipsograph, herein described, will appear as shown in Fig. 1. It consists of two main parts, the base and the arm. The former is a hardwood piece, A, Fig. 2, to the side center of which is attached another hardwood piece, B. This latter piece may be dovetailed into A, but an ordinary butt joint will suffice, as a one-piece base, C, also of hard wood, is glued to the bottom surfaces of the pieces A and B, thus securely holding them together. Before gluing, however, care must be taken to see that the piece B is exactly at right angles with the piece A. This can be done with a try-square. Dimensions are given in Fig. 2. The same letters are used throughout for the same parts.

A 1/16-in. groove, H, is cut out at the juncture of A and B, to admit the flange of the minor-axis swivel head. Another groove, J, is made along the longitudinal center of the piece B, to receive the spine of the major-axis swivel head. Sheet brass plates, D and E, are cut from 1/16-in. stock and attached to the top of the piece A with screws. The plates F and G are of the same material and fastened in a like manner to the upper surface of the piece B. All plates project slightly where they touch the groove borders, as shown. This is to provide a bearing for the projections on the sliding parts against metal instead of wood. A piece of thin celluloid or brass plate, K, is inserted in the bottom side of the base C so that the point will be exactly in line with the center groove J, and extend outward 1/8 in. This point indicates the center of all ellipses to be drawn. In the bottom of the base C, at each end, drive an ordinary pin and cut it off so that a part of it will project beyond the surface of the wood. These extending ends are pointed with a file, and serve to keep the instrument from slipping when in use.

The arm L is shown in Fig. 3. It is made of either maple or birch. Follow the dimensions given, cutting a slot through it longitudinally, as shown at M, narrower on the upper side than on the lower, the upper being 1/4 in. wide. An octagon-shaped piece of wood, N, 1/2 in. thick, is glued to the end, to give a good seating for the sleeve O, which is a piece of 1/2-in. solid-brass rod, 2 in. long, drilled to receive closely the pencil sheath. The latter, P, can be made from a section of brass tubing such as is used in a bicycle-pump valve. The upper end is notched to receive a rubber band, and an ordinary pencil can be cut down to fit closely into the other end. The piece O fits tightly in a hole bored through N and L.

The detail of the minor-axis swivel head is shown in Fig. 4. This swivel head consists of two pieces of brass, one, marked Q, being 3/8 in. square by 3/4 in. long and the other, R, 7/8 in. square by 1/2 in. long, with a notch cut out as shown. These parts, as well as the somewhat similar ones for the major-axis swivel head, can be cast cheaply, or block brass may be cut with a hacksaw and filed to the right shape. A shortened dry-cell screw, S, with washer, to fit a tapped hole drilled in the piece Q, serves to bind the head where desired on the arm. The flange T is a piece of 1/16-in. brass driven into a slot cut in the piece R. The piece R is pivoted to the piece Q, as shown, by means of a piece of wire nail which engages Q, by friction, the lower end being fitted with a washer and riveted loosely so that the parts will turn freely.

The major-axis swivel-head detail is shown in Fig. 5. The piece U is the same size as Q, Fig. 4, with its screw set a little farther forward to make room for the pivot V, which loosely joins U and W together. The pivot is made of a wire nail, riveted on both ends. The piece W is of brass, 1/2 in. thick, 3/4 in. wide and 7/8 in. long. The spine X is made just thick enough to pass freely in the groove J, Fig. 2. A screw taken from a discarded dry-battery cell is used to bind the head to the arm.

To operate the ellipsograph, draw a line, Y, Fig. 1, on the paper, which is to mark the major axis of the ellipse. About midway of its length make a point to represent the center. On the latter set the point K, Fig. 2, and adjust the bottom forward edge of the base C parallel with the line Y. Set the minor-axis swivel head at such a point on the arm L that, when the latter is directly on top of the piece B, the pencil will touch the paper at a distance from the center, marked by K, equal to half the minor axis of the proposed ellipse. To secure the major axis swing the arm until it is parallel with the piece A, leaving the major-axis swivel head unset, and set it when the pencil point has been adjusted to the proper major radius.

Grasp the arm with the right hand between the swivel heads and bearing down, swing the pencil end from right to left. The rubber band will keep it constantly on the paper with even pressure. When half of the ellipse is completed detach the rubber band and reverse the instrument to the opposite side of the longitudinal line Y and draw the other half in the same manner.

Protector Cap for a Chisel Handle

The ordinary chisel handle will soon split and break under the continuous blows of a mallet. A very good and inexpensive method of preventing this is to procure an ordinary patent bottle cap and place it on the end of the handle. It is advisable to shape the end of the handle like a bottle top in order to firmly hold the cap in place.--Contributed by Bert Verne, San Diego, Cal.

Sweeping Compound

A good sweeping compound may be made as follows: Mix 1/2 pt. of warm paraffin oil with 2 oz. of melted paraffin wax and add 2 oz. of artificial oil of sassafras. Then pour the mixture into 10 lb. of sawdust and work the whole thoroughly together. Add to this mixture 4 lb. of clean sand and 1/2 lb. of coarse salt. Each article mentioned is comparatively cheap, and the compound can be kept in an open container.--Contributed by Loren Ward, Des Moines, Iowa.

Freezing a Basin to a Chair

Fill a basin or pot half full of snow, and secretly put a handful of table salt in it and place the vessel on a chair or table, wetting the space where it is to be set. After holding the basin in place for about two minutes, continually stirring the contents, it will freeze to the chair so solidly that when the basin is lifted the chair will come along with it.

This experiment is quite interesting to an audience and can be performed at any assemblage with success. If the instructions are carried out closely, the trick will always succeed and the audience will consider it magic. Even if performed in a warm room, the combination of snow and salt will reduce the temperature below the freezing point where the bottom of the vessel comes in contact with the chair seat.--Contributed by Harry Slosower, Pittsburgh, Pa.

An Envelope and Stamp Moistener

A moistener for postage stamps or envelopes can be easily made from a screw-top jar. A strip of felt cut as wide as the jar is deep and made into a roll large enough to fit the neck of the jar serves as a wick. The metal top is perforated, and, after filling the jar with water, it is screwed into place. This makes a very inexpensive moistener for the library desk.

A Homemade Drill Press

An ordinary breast drill is used in the construction of this drill press, it being rigidly secured to a piece of oak, A, 2 in. square and 18 in. long, which is a sliding member on the pipe B. In attaching the breast drill to the wood, a bolt, having a hook on the head end, was used at the top, at C, and a stud at the bottom D. Pipe clips, EE, were attached on one side of the block to fit loosely over the pipe B. The vertical part of the pipe is supported by two horizontal pieces, FF, which are fastened to a post. A feed lever, G, is pivoted at the top of the vertical piece of oak A and fulcrumed on the post with a bolt through a slot, the extending end carrying a weight as a counterbalance. The illustration clearly shows the construction of this very useful drill press.--Contributed by W. A. Ready, Boston, Mass.

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A pair of bicycle trousers guards makes excellent sleeve bands when the cuffs are turned back and rolled above the elbows.

Arts-Crafts Leather Work By Mary C. Scovel