Magnetic-Suspension Pendulum

The Two Positions Occupied by the Slide-Opening Cover as It is Used on a Camera (Fig. 1, Fig. 2)

When a pendulum is not periodically supplied with energy its amplitude grows smaller and finally the motion ceases, due to the resistance of the air and the friction at the point of suspension. Usually the suspension is in the form of a knife edge bearing against plates of agate; sometimes the pendulum rod is simply attached to a very slender and flexible spring without any bearings. But the minimum of friction is obtained by means of magnetic suspension, as the following experiment will prove.

If the rod of a pendulum about 12 in. long, beating half seconds, is sharpened to a needle point and suspended from one of the poles of a magnet, it will be found that, if set into motion, it will continue to swing 15 times as long as the ordinary knife-edge suspended pendulum, and it will not stop until after about 16 hours, while one working on agate plates will stop in from 50 to 60 minutes. Similarly a top, provided with a fine-pointed axis of iron, will spin much longer when suspended from a magnet.

Magnetic suspension is used in precision instruments; for example, the minute mirrors which are used in certain telegraph systems to register writing photographically at the receiving end.

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In mechanical drawings cast iron is indicated by a series of straight lines across the parts made of this material. These lines can be quickly made with the usually discarded pencil stubs, if these are saved and sharpened in the following manner: The point is filed flat, as shown at A; then a slot is filed in the center of the lead with a knife file, as shown at B, and the points sharpened as in C. In this way two lines are drawn at one stroke neatly and in half the time.—Contributed by J. Kolar, Maywood, Ill.

To sharpen a carving knife draw the edge through and against the open edge of a pair of shears.

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The paddle-wheel boat, illustrated herewith, was built in the spare time I had on rainy afternoons and Saturdays, and the enjoyment I derived from it at my summer camp more than repaid me for the time spent in the building. The materials used in its construction were:

The dimensions given in the drawing will be found satisfactory, but these may be altered to suit the conditions. The first step will be to cut and make the sides. Nail the two pieces forming each side together and then cut the end boards and nail them to the sides. Lay this framework, bottom side up, on a level surface and proceed to nail on the bottom boards across the sides. The ends of these boards are sawed off flush with the outside surface of the sides after they are nailed in place. The material list calls for tongue-and-groove boards for the bottom, but plain boards can be used, although it is then difficult to make the joint water-tight. When the tongue-and-groove boards are used a piece of string, well soaked in white lead or paint and placed in the groove of each board, will be sufficient to make a tight joint.

Having finished the sides and bottom, the next step will be to fasten on the bottom keel. Adjust the board to its position and nail it in the center part where it lies flat on the bottom boards, then work toward the ends, gradually drawing it down over the turn and nailing it down. If the keel board cannot be bent easily, it is best to soak it in hot water where the bend takes place and the wood can then be nailed down without the fibers breaking. The inside keel is put on in the same manner, but reversed.

The Boat As It Appears without the Spring and Running Board and Used as a Pleasure Craft or for Carrying Freight, the Operator Facing in the Direction of the Boat's Travel

The next procedure is to make the paddle wheels. The hub for eachwheel is made of a 2-in. square piece of timber, 9 in. long. Trim off the corners to make 8 sides to the piece, then bore a 3/4-in. hole through its center. The 8 blades of each wheel, 16 in all, are 17 in. long, 6 in. wide and 3/4 in. thick. One end of each blade is nailed to one side of the hub, then it is braced as shown to strengthen the wheel.

Detail Drawing of the Boat and One of the Paddle Wheels. All the Material Required for the Construction is Such That can be Cut and Shaped with Ordinary Tools Found in the Home Workshop

The cranks are made of round iron, 3/4 in. in diameter, and they are keyed to the wheels with large nails in the manner shown. I had a blacksmith shape the cranks for me, but if one has a forge, the work can be done at home without that expense. The bearings for the crankshafts consist of wood, although it is preferable to use for this purpose two large iron washers, having a hole slightly larger than the diameter of the shaft, and drill holes in their rims so that they can be screwed to the wheel-box upright as shown. The bearings thus made are lubricated with a little lard or grease.

Detail of Paddle-Wheel Fastening, the Springboard Construction and the Fastening for the Rudder Control

The paddle-wheel boxes are built over the wheels with the dimensions given in the drawing, to prevent the splashing of water on the occupants of the boat.

The trimmings for the boat consist of three seats, a running board and a springboard. The drawings show the location of the seats. The springboard is built up of 4 boards, 3/4 in. thick, as shown, only nailing them together at the back end. This construction allows the boards to slide over each other when a person's weight is on the outer end. The action of the boards is the same as of a spring on a vehicle.

It is necessary to have a good brace across the boat for the back end of the springboard to catch on—a 2 by 4-in. timber being none too large. At the point where the springboard rests on the front seat there should be another good-sized crosspiece. Theboard can be held in place by a cleat and a few short pieces of rope, the cleat being placed across the board back of the brace. A little diving platform is attached on the outer end of the springboard and a strip of old carpet or gunny sack placed on it to prevent slivers from running into the flesh. In making the spring and running board, it is advisable to make them removable so that the boat can be used for other purposes.

The boat is steered with a foot-operated lever, the construction of which is clearly shown. For the tiller-rope guides, large screweyes are used and also for the rudder hinges, the pin of the hinge being a large nail. The hull can be further strengthened by putting a few angle-iron braces either on the in or outside.

To make the boat water-tight will require calking by filling the cracks with twine and white lead or thick paint. The necessary tools are a broad, dull chisel and a mallet. A couple of coats of good paint, well brushed into the cracks, will help to make it watertight as well as shipshape. The boat may leak a little when it is first put into the water, but after a few hours of soaking, the boards will swell and close the openings.

This boat was used for carrying trunks, firewood, rocks, sand, and for fishing, and last, but not least, for swimming. The boat is capable of carrying a load of three-quarters of a ton. It draws very little water, thereby allowing its use in shallow water. It has the further advantage that the operator faces in the direction the boat is going, furnishing the power with his hands and steering with his feet.

Loom Constructed of Sticks for Weaving Grass or Moss into a Camp Mattress

The camper who desires to "rough it" as much as possible and to carry only the necessities will find it quite a comfort to construct the bedding from grass or moss by weaving it in the manner of making a rag carpet, using heavy twine or small rope as the warp. Two stakes are set the width of the bed or mattress to be made, and a cross stick is attached to their tops. Several stakes are set parallel with the cross stick and at a distance to make the length of the mattress. The warp is tied between the tops of the stakes and the cross stick. An equal number of cords are then attached to the cross stick and to another loose cross stick which is used to move the cords up and down while the grass or moss is placed in for the woof. The ends of the warp are then tied to hold it together. When breaking up camp the cords can be removed and carried to the next camp.—Contributed by W. P. Shaw, Bloor West, Can.

Carrying a milk bottle by the rim is tiresome work for the fingers, so I constructed a handle, as shown in the sketch, from a piece of wire. The carrier can be easily placed in the pocket.

A Carrier Made of Wire to Quickly Attach on a Milk-Bottle Neck

The part fitting under the rim of the bottle neck is bent to form two semicircles, one hooking permanently at A, while the other is hooked at B after it is sprung around the neck of the bottle.—Contributed by Lawrence B. Robbins, Harwich, Mass.

kite

The material required for the making of a war kite is three pine sticks, each 60 in. long, one stick 54 in. long, one stick 18 in. long, all 1/2 in. square; 4 yd. of cambric; a box of tacks; some linen thread, and 16 ft. of stout twine.

Place two 60-in. sticks parallel with each other and 18 in. apart, then lay the 54-in. piece across at right angles to them 18 in. from the upper ends, as shown in Fig. 1, and fasten the joints with brads. At a point 21 in. below this crosspiece, attach the 18-in. crosspiece.

The extending ends of all the three long pieces are notched, Fig. 2, and the line is stretched taut around them, as shown by the dotted lines.

The Line should be a Very Strong One, Then Banners can be Flown on It

If the cambric is not of sufficient size to cover the frame, two pieces must be sewed together, then a piece cut out to the shape of the string, allowing 1 in. to project all around for a lap. The cambric is sewn fast to the string with the linen thread. Fasten the cloth to the frame part with the tacks, spacing them 1 in. apart. The space in the center, between the sticks, is cut out. Make two pieces of the remaining goods, one 36 in. by 18 in., and the other 36 in. by 21 in. The remaining 60-in. stick is fastened to these pieces of cambric, as shown in Fig. 3, and the whole is fastened to the main frame so as to make a V-shaped projection. The bridle strings, for giving the proper distribution of pull on the line to the kite, are fastened, one to the upper end of the long stick in the V-shaped piece attached to the kite, and the other to the lower end, as shown in Fig. 4. The inclination can be varied to suit the builder by changing the point of attachment of the kite line to the bridle. If it is desired to fly the kite directly overhead, attach the line above the regular point and for low flying make the connection below this point. The regular point is found by trial flights with the line fastened temporarily to the bridle, after which the fastening is made permanent.

The Sticks are Fastened Solidly with Brads, and the Cloth Sewed to the String around Their Ends (Fig. 1, Fig. 2, Fig. 3, Fig. 4)

The usual paper glider shaped as shown in Fig. 1 can be made to loop the loop and make corkscrew flights if prepared according to sketches herewith. It should be carefully made in the first place so that in its regular form it flies perfectly straight.

Ordinary Paper Glider and the Manner of Throwing It to Make the Different Flights (Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8)

To make the glider loop, the rear corners of the wings should be turned up at right angles, as in Fig. 2, and the glider launched with a great deal of force with the nose pointed slightly upward. This will require some practice, but one soon learns the trick. After looping once, as shown in Fig. 3, the glider descends in volplane. This form of glider will also right itself, if dropped from a height, nose downward, as shown in Fig. 4.

For a corkscrew flight the glider is prepared as in Fig. 5; one rear corner being bent up and the other down. In this form it flies horizontally, or downward, while rapidly rotating around its longitudinal axis, as shown in Fig. 6.

To make a spiral descent, the rear corners of the wings are bent up as in Fig. 2, and, further, the rear corner of the keel is bent at right angles, Fig. 7, whereupon it is thrown in the ordinary manner. It then takes the course shown in Fig. 8.

A cheap and very effective water filter can be made of a flower pot by plugging the hole in the bottom with a piece of sponge and fitting it as follows: Place powdered charcoal on top of the sponge to a depth of 1 in., then 1 in. of clean silver sand, and lastly 2 in. of small stones and gravel. It is hung with a bail at the top.

The illustration shows a very useful application of an ordinary electric door lock in the construction of a combination lock and alarm to be operated from the outside of the building.

The Brass-Tack Heads Holding the Numerals in Place Constitute the Combination Points

The three numerals, 1, 2, and 4, or any other combination of numbers constituting the house number on a door, are made of some kind of insulating material and fastened in place on a base of insulating fiber, or wood, about 1/4 in. thick, by means of ordinary brass-headed tacks, as indicated by the black dots. The tacks will extend through the base a short distance so the electrical connections may be made by soldering wires to them, as shown by the diagram, alternate tacks being connected together with the exception of three; for instance, A, B, and C.

The terminals of the leads that are connected to alternate tacks are in turn connected to the terminals of a circuit composed of an ordinary vibrating bell, D, and battery, E. If any two adjacent tack heads be connected together, except tacks A, B, and C, the bell circuit will be completed and the bell ring, which will serve as an indication that some one is tampering with the circuit. The person knowing the combination, connects the tack heads A and B, and at the same time connects the tack head C with F or G, or any other tack head that is connected to the plus side of the battery, whereby a circuit will be completed through the lock H and the door is opened. Any metallic substance, such as a knife, key, or finger ring, may be used in making the above indicated connection, and there will be no need of carrying a key for this particular door so long as the combination is known.

The base upon which the numbers are mounted and through which the points of the tacks protrude, should be mounted on a second base that has a recess cut in its surface to accommodate the wires and points of the tacks.

The combination may be made more or less complicated, as desired, by connecting the tacks in different ways, and by using a separate battery for the bell and lock. The circuit leading to the door lock, if there is one already installed, may be used and then no extra circuit is needed.

Such a device has been used on a private-desk drawer with entire satisfaction. The battery was placed in the back end of the drawer, and if it happened to fail, a new one could be connected to the points B and J so that the drawer could be opened and a new battery put in.

The Bend in the Pin will Hold in the Hair and Prevent the Loss of the Pin

To avoid losing a fancy hairpin, bend one leg of the pin as shown in the illustration. The hair caught in the notch formed by the bend will prevent the pin from dropping out.—Contributed by W. C. Loy, Rochester, Ind.

A metal surface polished with oil will keep clean longer than when polished dry.

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After building a number of kites from a recent description in Amateur Mechanics I branched out and constructed the aeroplane kite shown in the illustration, which has excited considerable comment in the neighborhood on account of its appearance and behavior in the air.

The Kite Being Tailless Rides the Air Waves Like an Aeroplane in a Steady Breeze

The main frame consists of a center-stick, A, 31 in. long, and two cross-sticks, of which one, B, is 31 in. long and the other, C, 15-1/2 in. long. The location of the crosspieces on the centerpiece A is shown in the sketch, the front piece B being 1-3/4 in. from the end, and the rear piece C, 2-1/4 in. from the other end. The ends of the sticks have small notches cut to receive a string, D, which is run around the outside to make the outline of the frame and to brace the parts. Two cross-strings are placed at E and F, 7 in. from either end of the centerpiece A, other brace strings being crossed, as shown at G, and then tied to the cross-string F on both sides, as at H.

General Plan and Outline of the Kite, Which may be Built in Any Size, If the Proportions are Kept, and Its Appearance in the Air on a Steady Breeze

The long crosspiece B is curved upward to form a bow, the center of which should be 3-1/4 in. above the string by which its ends are tied together. The shorter crosspiece is bent and tied in the same manner to make the curve 2-1/2 in., and the centerpiece to curve 1-3/4 in., both upward. The front and rear parts, between the end and the cross-strings E and F, are covered with yellow tissue paper, which is pasted to the crosspieces and strings. The small wings L are purple tissue paper, 4 in. wide at M and tapering to a point at N.

The bridle string is attached on the centerpiece A at the junction of the crosspieces B and C, and must be adjusted for the size and weight of the kite. The kite is tailless and requires a steady breeze to make it float in the air currents like an aeroplane.

The bridle string and the bending of the sticks must be adjusted until the desired results are obtained. Thebridle string should be tied so that it will about center under the cross-stick B for the best results, but a slight change from this location may be necessary to make the kite ride the air currents properly. The center of gravity will not be the same in the construction of each kite and the string can be located only by trial, after which it is permanently fastened.

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Homemade Still for Removing the Impurities in Water That is Used in Mixing Chemicals

Pure water, free from all foreign substances, is frequently wanted for making up photographic solutions and many other purposes. An apparatus for distilling water can be very easily made from galvanized pipe fittings. The outer cooling jacket A is a piece of 1-in. pipe, 2 ft. long, threaded on both ends, and bored and tapped for 1/2-in. pipe at B and C. A hole is bored and tapped for 1/2-in. pipe in each of the two caps used on the ends of the pipe A, and a piece of 1/2-in. pipe, D, 2 ft. 8 in. long, is run through the holes as shown. The joints are soldered to make them water-tight. Two 1/2-in. nipples, 4 in. long, are screwed in at B and C. The retort, or boiler, E, in which the impure water is boiled may be made of any suitable vessel and heated with a Bunsen or gas burner. A beaker, or other vessel, F, is placed below the lower end of the small pipe. The cold water from the faucet, which flows into the outer jacket at C and out at B, condenses the steam in the small pipe D, turning it into water which falls into the beaker in large drops. The water is often distilled a second time to remove any impurities which it might still contain.—Contributed by O. E. Tronnes, Evanston, Ill.

Having a sloping-top desk and being compelled to use the telephone quite frequently, I devised a support for the telephone so that it might stand level and not fall off. The sides of the stand were cut on the same slope as the desk top, and their under edges were provided with rubber strips to prevent slipping.—Contributed by J. M. Kane, Doylestown, Pa.

Stand with a Level Surface for a Desk Telephone to be Used on a Sloping Desk Top

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The monoplane glider illustrated has better fore-and-aft stability than the biplane, is lighter in proportion to the supporting surface, simpler to build, and requires very little time to assemble or take apart. The material list is as follows:

FRAME

WINGS

The first thing to do is to make the main frame which is composed of the four bamboo poles. The poles take the corners of a 2-ft. square space and are supported with the pieces of spruce that are 2 ft. and 3 ft. long, the shorter lengths running horizontally and the longer upright, so that each upright piece extends 1 ft. above the two upper poles. All joints should be fastened with 3/16-in. stove bolts. The wire used to truss the glider is No. 16 gauge piano wire. The trussing is done in all directions, crossing the wires between the frame parts, except in the center or space between the four poles.

The Start of the Glide should be Made from the Top of a Hill, Then a Little Run will Carry the Airman Several Hundred Feet through the Air

The framework of the main wings is put together by bolting one of the crosspieces at each end of two wing bars, then another 4 ft. from each end, whereupon the wing bars are bolted to the main frame. The frame is then braced diagonally between these pieces. The ribs, spaced 1 ft. apart, are fastened to this frame with 1-in. brads. The ribs are so bent that the highest part will be 5 or 6 in. above the horizontal. The bending must beuniform and is done when fastening them in place.

The material used to cover the wings and rudders is strong muslin. The cloth is first tacked to the front wing bar, then to the ribs, and sewed to a wire which is fastened between the ends of the ribs. Large brass-head tacks should be used through a strip of tape to fasten the cloth to the ribs. The rear wings are constructed in a similar manner. After the cloth is in place it is coated with starch or varnish.

Details of Tandem Monoplane Glider, Showing the Main Frame and Wing Construction, and the Manner of Placing the Crossed Bracing Wires Between the Parts and to the Wing Ends

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The two vertical rectangular spaces in the main frame, just under the rear wings, are covered with cloth to act as a rudder. The upper and lower bracing wires for the wings are attached with snaps and rings so that the glider can be easily taken apart.

It is best not to use the glider in a wind greater than 30 miles an hour. It is started from the top of a hill in the usual manner. Glides can be made running from 60 to several hundred feet.

Where it is necessary to carry a well filled and heavy suitcase the light truck shown in the sketch will be a great assistance. The truck is constructed on the folding plan, similar to a go-cart, and can be carried on the side of the case. The wheels are those used on a go-cart, with rubber tires and about 6 in. in diameter. These are fitted to standards carrying a hinged top piece, the upper ends of the standards being hinged in a like manner. The standards should be cut to the proper length for the person carrying the suitcase.—Contributed by Mrs. Harriet M. S. Kerbaugh, Allentown, Pa.

The Small Truck will Greatly Assist the Carrying of a Heavily Loaded Suitcase

Remove the lock and cut the mortise deep enough to admit a 3-volt battery lamp with a suitable socket attached. The lamp is then connected to wires which are concealed and run to a battery of three dry cells in the basement or other convenient place. A small push button is attached in the line and placed near the knob on the door. A small recess must be cut in the mortise so that the light from the lamp will shine directly on the inside of the plate over the keyhole.—Contributed by Armand F. Lamarre, St. Remi, Can.

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A simple glider of the monoplane type can be easily constructed in a small workshop; the cost of materials is not great and the building does not require skilled workmen. Select the material with care and see that the wood is straight-grained and free from knots. The following list of spruce pieces is required:

The following list of poplar pieces is required in making the supports for the cloth covering on the wings and rudders.

The following list of oak pieces is needed:

In addition to the lists given, four pieces of bamboo, 16 ft. long, tapering from 1 or 1-1/4 in. at the large end to 3/4 in. at the small end, are used for the main frame.

Monoplane Glider in Flight

The first part to make is the main frame A which is constructed of the four bamboo poles. They are made into a rectangular frame with crossbars marked B cut to the right length from the 12-ft. piece of spruce, 1/2 in. by 1 in. The bars C and D are of oakcut from the 6-ft. piece, 5/8 in. by 1-1/4 in. All of these crossbars are fastened together in rectangular form by means of stove bolts. The bamboo poles are then bolted to the inner corners of the frames with 3/16-in. bolts. Place the bolts through the bamboo close to a joint to prevent splitting. The frame is then rigidly trussed by diagonal wires marked E crossing all rectangles. The wire used for trussing all the parts throughout the glider is piano wire, 16 gauge. The arm pieces are bolted to the sides of the rectangular frames beneath the wings.

Plan View

Side Elevation

Front Elevation

Wing Bar

The framework of the main wings or planes should be put together by bolting the cross struts F at regular intervals on the under side of the main spars G. Brace the frame diagonally with the piano wire. The ribs are nailed to the main spars by using 1-in. brads. The ribs are spaced 1 ft. apart, and curved so that the highest part will be 5 in. from the horizontal. Each rib extends 15 in. back of the rear spar. The rudder is made in the same manner.

The vertical rudder is made to fold. A small pocket arrangement H is made from which the rigs of the vertical rudder diverge.

The covering of the wings and rudders should be a good quality of muslin or some light aeronautical goods. The cloth should be tacked to the front spar, to the ribs, and then sewn to a wire which connects the ends of the ribs.

Construct the triangular arrangement marked J to which the wings are braced. The wing bar supports are shown in the illustration. The bottom wires are braced to the crossbar K shown in the front elevation.

The bracing wires are all fastened to a snaphook which can be snapped into the rings at the places marked L. This method will allow one quickly to assemble or take apart the plane and store it in a small place. The vertical rudder should be braced from each rib to the front spar of the horizontal rudder and then braced by the wires M to hold the rudder from falling back. The rudder is then braced to the main frame and the main frame is braced by the wires N to the wings. This will hold the plane rigid. Use snaphooks and eyebolts wherever possible so that the plane can be quickly assembled.

The triangular arrangement J is bolted to the wings and the top wires put in place. The wings are then put on the main frame and bolted to the bars marked C and D, after which the bottom wires are fixed in place.

Take the glider to the top of a hill, step into the center of the main frame just a little back of the center of the wings. Put your arms around the arm pieces, face the wind and run a few steps. You will be lifted off the ground and carried down the slope. The balancing is done by shifting the legs. The glides should be short at first, but by daily practice, and, as the operator gains skill, glides can be made up to a length of several hundred feet. Do not attempt to fly in a wind having a velocity of more than 15 miles an hour.

The exerciser consists of a disk, 5 ft. in diameter, pivoted in the ground near the kennel. The disk revolves on a 5/8-in. pin set in a post made of a 4 by 4-in. piece of timber. The disk is made of common lumber fastened together with battens on the under side. Our dog seems to enjoy this kind of exercise.—Contributed by Hazel Duncan, Denver, Colo.

Revolving Disk Exerciser

The sketch illustrates a gas generator designed for laboratories where gases are needed in large quantities and frequently. The shelf holding the large inverted bottle is of thick wood, and to reinforce the whole apparatus, a 1-in. copper strip is placed around the bottle tightly and fastened with screws turned into the woodwork. The shelf above is attached last, and upon it rests the bottle of commercial acid required in the gas generation. The pump shown is for use in starting the siphon.

Gas Generator of Large Capacity That will Work Automatically as the Gas is Removed

The large bottle used as a generator may be either a 3 or 5-gal. size, and after it is placed in the position shown, a sufficient amount of the solid reagent needed in gas generating is placed in the mouth before the exit tube, leading away below, is fixed in position. If sulphureted hydrogen is required, ferrous sulphide is used; if hydrogen is required, zinc is placed within; and to make a carbon dioxide, marble, or its equivalent, is inserted. Whatever gas is required, a sufficient quantity of the solid material is put in to last for some time in order not to disturb the fastenings.

When all is ready, the pump is used gently to start the acid over the siphon and into the generator from below. The gas generated by the action of the acid on the solid soon fills the bottle. The screw clamp on the exit tube is loosened and the gas passes into the bottle of water and charges it, in the case when sulphureted hydrogen is required. In the other cases, when sufficient gas has been generated, the screw clamp is tightened, and the gas soon attains considerable pressure which forces the acid back out of the generator and into the acid bottle above. The whole apparatus now comes to an equilibrium, and the gas in the generator is ready for another use.—Contributed by W. M. Mills, Bakersfield, Cal.

Procure a strip of sheet metal, 6 in. long, 1 in. wide, or as wide as the armature core is long, and 3/32 in. thick. Bend this into a U-shape, as shown, and file each end similar to the barb on a fishhook. Drill two holes for a bolt to pass through the sheet-metal ends. Fasten a screw or bolt in the center of the bend, to be used for gripping in a chuck or polishing head. Core segments can be quickly wound with this device.—Contributed by Geo. B. Schulz, Austin, Illinois.

Armature Cores are Easily Revolved to Fill the Core Openings with Insulated Wire

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A clerk finding the cement floor of the office uncomfortably cold to the feet, devised a footstool in the following manner: A shallow box was procured, and four small truck casters were fastened to the bottom. A piece of carpet was laid on the inside of the bottom and some old newspapers placed on top of it. When seated at the desk, he placed his feet inside the box on the papers. The casters elevated the box from the cement, just high enough to avoid dampness and cold, and permitted an easy change of position.—Contributed by L. Alberta Norrell, Gainesville, Ga.

The material required to construct a telegraph sounder, like the one shown in the sketch, consists of two binding posts, magnets, a piece of sheet metal, and a rubber band. These are arranged as shown, on a wood base or, better still, on a metal box. In using a metal-box base, be sure to insulate the connections at the magnet coils and binding posts.

An Inexpensive and Homemade Sounder for Use in Learning the Telegraph Codes

This instrument will be found by those studying the telegraph codes to give good results, equal to any of the expensive outfits sold for this purpose.—Contributed by Chas. J. La Prille, Flushing, N. Y.

The sketch represents a force filter which is well adapted for use in small laboratories. The water is turned on at the faucet and draws the air through the side tube by suction, which in turn draws the air in a steady stream through the Wolff bottles. The tubes may be attached to a filter inserted in a filter bottle and filtering thus greatly facilitated. The connection to the faucet can be made, as shown in the detailed sketch, out of a long cork, by boring a hole large enough to fit the faucet through the cork and another slanting hole, joining the central hole, on the side for a pipe or tube. At the lower end of the cork a tube is also fitted, which may be drawn out to increase the suction. The inclined tube should be slightly bent at the lower end.—Contributed by W. M. Mills, Bakersfield, Cal.

A Slight Vacuum is Formed by the Water Flowing through the Cork, Which Forces the Filter

One of the most amusing as well as useful devices for a beginner on roller skates is shown in the sketch. The device is made of 3/4-in. pipe and pipe fittings, with a strip of sheet metal 1 in. wide fastened about half way down on the legs. On the bottom of each leg is fastened an ordinary furniture caster which allows the machine to roll easily on the floor. The rear is left open to allow the beginner to enter, then by grasping the top rail he is able to move about on the floor at ease, without fear of falling.—Contributed by J. H. Harris, Berkeley, Cal.

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