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tension of the clamp. A hole must be cut in the platform for the insertion of the clamp. The shank should be pierced with several holes so as to allow for larger pieces of wood. The treadle g, at the bottom, is kept in place by a peg at h.

To put the finished horse to use, the workman inserts the piece of wood under the edge of the clamp, and presses back upon the treadle with his foot. The wood is thus securely caught. The shaving can now be done with the drawing knife, more easily and expeditiously than would. be the case if a vise were used.

Improved Furnace Ventilation What is the latest and best method of ventilating with hot-air heating?-H. S. G.

ber of the American Society of Heating and Ventilating Engineers, at its meeting in Chicago last July.

The system herein described differs from the ordinary type in that ventilation is satisfactorily secured for all the rooms of the house. Any up-to-date furnace, large enough for the service it will be called upon to perform, may be installed. Fresh air should be obtained directly for the furnace, which ought to be centrally located. The warm-air chamber or box need be connected with the registers in the various rooms by only one-half the number of pipes ordinarily used. The basement is not filled with hot-air pipes, as is the custom in present modes of hotair heating.

The illustration shows the method of connecting the wall pipe to the top of the

There are numerous methods, each of improved side-wall register. The method

of pipe construction in the basement is also indicated. The registers in the various rooms are provided with a double metal box. Between the inner and outer casing there is an air-space. A ventilating opening is provided for. This opening sucks the atmosphere from the heated room and conducts it through the airspace upwards. Where single wall pipes are used, the air passes around the pipe. Where double wall pipe is used, the air passes between the two casings. The heated wall pipe causes the air of the room to move off rapidly. Vent pipes should conduct the bad air to a chimney flue. This flue should be used for this purpose only.

IMPROVED FURNACE HOT-AIR SHAFT.

which has advantages peculiar to itself. Probably one of the most satisfactory systems is that recommended by a mem

Wireless' Greatest Distance

To what distance can the wireless telegraph be successfully operated?-F. N.

This is a question that cannot be answered very definitely. Messages are supposed to have been sent across the Atlantic, by Marconi. Vessels at sea several hundreds of miles apart, readily communicate with one another by wireless. The efficiency of the service varies considerably with place and atmospheric conditions. What the instruments in use to-day are fully capable of doing, cannot be stated. Results from day to day, with the same instruments, show very great discrepancies.

Taking an Indicator Card Explain in full the method of taking an indicator card.-R. C. T.

The instrument should first be examined and put into proper condition and adjustment. This should include the following points: (1) The joints should all work freely, but with-out lost motion; (2) the piston should not bind, nor should it be so loosely fitted as to allow serious leakage. A slight leakage, however, is better than too snug a fit; (3) the working surfaces of the barrel and piston should be carefully wiped and oiled. This should be repeated from time to time when a series of cards is being taken. The joints of the pencil motion should also be lu- A bricated with clock oil as often as may be required.

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(4) The pencil points should be sharpened and the screw stop so adjusted that the point can rest only lightly on the

paper.

The operation of taking the card itself is briefly as follows:

The indicator is attached to the cock; a blank card is placed on the drum; and the cord connection is adjusted so that the drum will have the proper stroke without coming against the stop at either end. In attaching the blank card, the most convenient way will be to bend the sheet of paper around and grasp both edges between the thumb and forefinger as at AB. Then slip over the drum and under the clips, so that the latter will come outside the paper as shown at PQ,b.

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from which the diagram is desired, and the pencil immediately takes up its motion corresponding to the varying pressures of the steam. The indicator piston should be allowed to work in this way for a few strokes, or until everything is warmed up into working condition.

When everything is in readiness, the pencil motion is moved up against the stop so that the pencil, resting lightly on the paper, will trace its path for a complete revolution, or longer if desired. Then remove, and shut off the indicator from the cylinder. This will connect it with the air; the indicator piston will come to equilibrium under atmospheric pressure; and the atmospheric line may then be drawn. The drum connection is then unhooked, the paper removed, a fresh one replaced, and the next card taken when desired.

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ADJUSTING AN INDICATOR CARD.

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If one indicator is used for both ends of the cylinder, both cards should be taken on the same paper with as small an interval between as possible. The cock is swung over for one end, and the card taken;

and then immediately swung over for the other end, and the second card taken without loss of time. The cock is then closed off, connecting the indicator with the air; and the atmospheric line is then drawn.

Each card, as it is removed from the indicator, should be marked with sufficient data to identify it, and make possible its use for the purpose intended. This should include at least the following items: (1) Cylinder; (2) end from which card is taken; (3) revolution; (4) scale of spring; (5) if a series of cards are being taken, the time and serial number should also be set down.

The various other items usually printed on the back of the card may be filled in at a later time, as may be convenient. When cards from both ends are taken on one paper, we must be able to assign each to its proper end of the cylinder. The surest way of determining this is to shut off the connection to one end of the cylinder entirely, and then take the card from the other end. It will thus appear how the card from this end lies on the paper-whether with admission line to the right or to the left; and this will show how to mark the entire series of cards taken with the same arrangement of reducing gear, etc.

main piece A. At one end of this eightinch piece, drive a staple D; at the other end, a hook G. Next take a rope, fasten a ring at one end F, and run around the crank-shaft and through the staple, as indicated. The apparatus is now ready for

use.

Thrust the point of the tapering stick

MISSION STYLE LIBRARY TABLE.

into the shock, and bind the around rope the latter by catching the ring on the hook. On turning the crank, the rope will wind itself about the larger stick between the washer and the crank.

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Making a "Mission" Table

Will you please explain the construction of a "mission" library table large enough for three or four persons to gather about?-T. J. M.

The accompanying drawing gives a general view of a standard style of such a table as you speak of. One whose top is about 48 inches long and 28 inches. broad, will doubtless answer your purpose. The height should be about 29 inches. Legs 3 inches square, set 14 inches from the corners, will offer a firm support. The shelf supporting the trough for books, is set 10 inches from the floor. A full drawer may be put in, or small, corner drawers, according to taste or needs. The board for the top is 14 inches thick. Pegs should be used throughout, instead of nails. Smoothplaned oak makes excellent material for furniture of this kind.

The staining to a dark hue may be done after the construction is completed.

Cleaning Sooty Bricks

Soft coal smoke has spoiled the appearance of my pressed-brick house. How can I remove the sooty deposit?-G. T. S.

Make a mixture as follows: One pint of liquid ammonia; 1 gallon soft soap; pounds powdered pumice. A soft, pasty substance should be the result. Brush the dust off the brickwork. Then apply the mixture with an ordinary new whitewash brush. At the end of some 20 minutes, take a scrubbing brush and use. it vigorously. Rinse down with a hose, or clean with a large sponge and lukewarm water. The bricks will come out as if new.

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coal, puddled bar, or blister steel, and charcoal. The crucibles are made of clay or graphite, with a capacity of 50 to 85 pounds. The charge is put into the crucible, and after melting is allowed to stand for a time, called the "killing period," and then poured into moulds.

In American practice, graphite crucibles are used, which are made from a mixture of fire-clay and sand, and about 50 per cent graphite. This mixture is ground, allowed to stand for a few days, and is then moulded by being pressed into a wooden mould. When dry, it is baked in a kiln. These crucibles can be used about five times, if the successive charges. are gradually diminished in amount.

The crucible is charged cold. The pieces of iron are surrounded with charcoal, with a little manganese, and sometimes a little salt or ferrocyanide of potassium mixed with it. The crucible, after being covered, is placed standing on the coal in a hot furnace. After three hours, during which the contents are melted, the cover is lifted, and the melter examines the charge to determine the length of the "killing" period. During this period, which is about 45 minutes, the metal is becoming tranquil and is taking silicon from the sand in the walls of the crucible. This silicon prevents blow-holes. At the right time and temperature, the crucible is lifted out and the slag skimmed off. The metal is now ready for casting or "teeming."

The ingots are graded and hammered. into bars for different uses. Crucible steel furnishes the finest grades for cutlery and machine tools; it is superior to Bessemer and open-hearth steel, because pure materials are used and the process is carried on in a closed vessel, thus protecting the metal from sulphur gases

from the fuel.

Pictures by Flash-Light Would you please explain how to take a picture by flash-light?-O. S.

Place a card for a reflector behind the flashlight, the latter being about 25 inches from the camera and level with it.

When ready, open the camera shutter, as in a time exposure, light the flash, and close the shutter at once.

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broken stone make generally the best proportions. In cases where gravel is easy to procure, this may be substituted for stone. In the center of a large block the proportion of stone and sand may be increased with very satisfactory results.

Mixed concrete should never be shoveled into a hole full of water, as the stone or gravel will sink first and the other material follow according to its specific gravity. Where it is necessary to lay the foundations under water, the dry mixture must be placed in bags and so deposited. While the concrete thus assumes an irregular form, this method has proved highly successful in building footings. The following method is employed where the forms extend clear to the bottom under water. A special shovel or bucket is filled with the concrete and lowered to the bottom, where it is emptied.

Concrete in foundations, even in large buildings, is rarely reinforced. Where the foundation is upon uneven ground,

reinforcing is advisable, and especially upon soil liable to settle or crack. Old steel rails may be used, where reinforcing is necessary. There is a tendency to use more metal for this purpose than is really needed, however.

Concrete should not be allowed to freeze during setting. Freezing after setting, however, seems to do it no special injury. In foundations, retaining walls, etc., a saturated salt solution is sometimes mixed with the concrete. This prevents freezing, and the material seems to suffer no injury from its presence.

2. Cinder concrete is made by taking boiler cinders and mixing them with cement. The concrete so made weighs far less than stone or gravel concrete. The material loses considerably in strength, however. It does well enough for floors, but should never be used in damp places, as the porous cinders readily absorb moisture. It is equally faulty in the construction of beams and pillars.

Place of Air-Chamber on Steam Pumps Where should the air-chamber on a steam pump be placed?-E. B. M.

The air-chamber on the discharge should be placed at the highest point of the valve-chest and above the delivery opening so that the air will not tend to slip out with the water. Even then the air will be gradually absorbed by the water; and provision must be made for renewing the air-cushion - either when the pump is not in use, by admitting air through a cock and allowing some water to escape from the valve-chest; or continuously, by an automatic pump.

The suction air-chamber should be so placed that the stream of water flowing to the pump will cushion against the air in it without changing its direction abruptly. Two positions which fulfil this condition are shown in the accompanying figure. If it is impossible to place the suction chamber in such a position, the capacity should be increased considon the erably, the amount depending on speed at which the pump is to be run.

New Cure for Appendicitis In Germany collangol, a silver solution, is curing appendicitis without the necessity of an operation.

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