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Stretching Barbed Wire Could you suggest how to make a stretcher for barbed wire?-F. W. G.

Saw from hickory, oak, or other hardwood a piece three-quarters of an inch

to drive through this steam. It often is unable to do this; and, as a result, work is brought to an abrupt standstill.

SIMPLE WIRE-STRETCHER.

thick by two and a-half or three inches wide, and of convenient length. Be sure there is no knot in the wood that can weaken it. At one end, fasten an iron plate containing a notch the width of a barb. Now catch in the notch a barb close to a post, and brace the plated end of the stick against the post. An excellent leverage can thus be secured and the wire will be tightened.

Operation of Electric Bell Please explain with diagrams the operation of an electric bell.-S. E. G.

The operation of an electric bell depends upon the principle that if a current of electricity flows through a coil of wire wound upon an iron core, the core becomes magnetized and will attract any magnetic substance to itself. A diagrammatic representation of an electric bell is shown in Fig. 1, in which M is the

For a Pinched Tube

How can I prevent the pinching of inner tubes in tires?-C. R. K.

The tube should first be carefully wiped with a clean cloth that has been well charged with talc powder. Then slightly inflate the tube, to remove folds and wrinkles. In introducing it into the shoe, feel inside around the rim, and underneath the tube, to be sure all is smooth and right. If a fold is discovered that refuses to yield to rubbing, remove the tube and repeat the process.

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Pumping Hot Water

Why is it that hot water cannot be successfully drawn through a pump?—W. H. A.

Under proper conditions, there is no reason why hot water cannot be pumped. But when the pump is not placed below the level of the supply, so that the water enters with little or no pressure, difficulty is likely to be experienced. When the piston rises, the pressure is reduced and the vacated space is flooded with steam. The reason for this is that a liquid will boil at a lower temperature than in the surrounding atmosphere if the pressure is reduced. This well-known fact is taken. advantage of in the boiling of syrups, etc. On its return, the piston is obliged

FIG. 1.

electro-magnet composed of a soft iron core of horseshoe shape wound with copper wire. The armature of the bell is mounted on a spring K, and carries a hammer H for striking the gong. On the back of the armature is a spring which makes contact at point D with a

backstop T. The action of the bell is as follows: When the circuit is closed through the bell, a current flows from terminal 1 around the cores of the electro-magnet, through the spring K and contact-point D, then through backstop T and terminal 2. The current magne

cuit with which it is connected in series. Normally the springs are separated as shown, and the circuit is open. The bell and the push-button are connected up in series with the batteries as illustrated in Fig. 3, in which P is the push, B the bell, and C the battery.

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tizes the core, which causes it to attract the armature, and the hammer strikes the gong. While in this position, however, the contact at D is broken, the current ceases to flow, and the cores lose their attractive force. The armature is, therefore, carried back to its original position by the spring K, making contact again, and the process is repeated. The bell will, therefore, continue to ring as long as the circuit is closed.

The bell-push, or means of closing the circuit, is shown in Fig. 2. P is the push

FIG. 3.

B

button; and when this is pressed upon, it brings the point of the spring S in contact with the spring R, thus closing the cir

Use of Soldering Paste

What is soldering paste, and how is it used? -W. S. C.

Soldering paste consists of a mixture of grease and chloride of zinc. Vaseline or petrolatum is the grease commonly used, the latter being probably just as effective and costing less. The composition is mixed as follows: One pound of petrolatum, one fluid ounce saturated solution chloride of zinc. The chloride of zinc solution is made by dissolving as much zinc in strong hydrochloric acid as it will take up. A thick, oily solution is the result. This is mixed with the petrolatum by vigorous stirring.

The mixture is used in electrical work as a flux for soldering, especially for soldering copper wires. It is also used in other fields where corrosion is not desirable.

Tropenas Process of Making Steel
Castings

Please explain or describe the Tropenas process of making steel castings?-W. A. H.

The difference between this method and the ordinary method is that instead of having the tuyères at the very bottom of the converter so that the blast goes up through the metal, the air is blown at a low pressure upon the surface of the molten metal. At a point 4 to 7 inches above this set of tuyères, is another set which supplies air to burn the carbon monoxide coming out of the metal. In this method there is a great increase in the amount of heat produced, and the steel is much hotter than if blown in the usual (Bessemer) way. These converters are better adapted than an open-hearth furnace for making very small charges.

Longest Subsurface Phone

By W. T. Walsh

ETWEEN the two great cities on Lake Michigan, Chicago and Milwaukee, there will soon be in operation the longest underground telephone system in the world. The feat of laying cables that would be capable of electrically transmitting the voice eighty-five miles, the distance from the Illinois to the Wisconsin city, would have been considered problematical several years ago; thirty

MEN LAYING CONDUITS. Chicago-Milwaukee telephone line.

miles was something of which to boast. But in 1900, Prof. M. I. Pupin of Columbia University, invented the load coil that bears his name, by which self-induction is almost entirely overcome-that is, the current of one cable is prevented from setting up an induced current in a parallel cable. Professor Pupin's invention may be compared to a balance, for it acts in such a way that both cables remain about equally charged, rendering "cross-talk" impossible. The appliance has often been used in the past for longdistance overhead systems; for subsurface cables, however, the construction of the Chicago-Milwaukee line marks an epoch.

The advantages of the conduit method lie in the lessened cost of maintenance, and in the increased efficiency of the

service rendered. Wind, nor rain, nor storm can disturb the cables. "A heavy snowfall brings down wires," will never be said of the Chicago-Milwaukee telephone line. Moreover, many fine towns, surburban in character, along the route, are preserved from the disfigurement of unsightly poles and webs of tangled wire.

The work of construction is divided between the Chicago and the Wisconsin telephone companies. The southern limits of Kenosha, Wis., indicate where one shall leave off and the other continue the labor. Trenching and laying the cables are not the only things that have to be accomplished. An adequate system of drainage also is provided for, and this through a rolling country traversed by ravines and varying considerably in the character of the soil.

Several gangs of men, ranging in numbers from fifty to 100, began the work simultaneously at various points. Excavation, of course, was the first step. Ordinarily, two feet is the depth of the ditch; but conditions are occasionally such as to render three times this depth necessary. Gullies, so frequently encountered, must be filled; rivers and ravines crossed by means of viaducts.

This initial work completed, all was ready for the installation of the conduits.

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Where concrete alone is used, the conduits are encased in a three-inch layer of the substance. In cross-country work, a four-inch bed of concrete is first laid. Upon this the conduits are placed, and covered with two inches of earth. Finally, a plank one and one-half inches in thickness, thoroughly impregnated with creosote, is set over all. Thus, in ordinary cases, the sides of the tile are protected only by the earthy walls of the trench itself. But where there is any likelihood of current interruption, as has been stated, the tile conduits rest securely encased in concrete armor, safe from water and surface pressure, and, in fact, from any danger except the unforeseen.

The drainage system has been alluded. to. At all hazards, the subtle trickle of water that steals electricity, the life of the telephone, must be prevented. At every two hundred yards' distance is placed a concrete basin. From 100 yards either way, the trench is drained into these basins. The fall is gradual, two inches in 100 feet. Town sewers, where available, afford valuable assistance in this draining.

At intervals of a mile and a-quarter, the Pupin load coils, the secret of the successful operation of the long-distance underground telephone line, are set in manholes of unusual size. Iron pots protect the coils.

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PANNING GOLD NEAR WASHINGTON, D. C.

environs of Washington City, where, if a man dig down to the gravel and black sand that lie over bed-rock, he cannot, by

TYPICAL GROUP OF MINERS.

panning, get a "color." It has not been found in sufficient quantities to make placer mining attractive, though many men have washed out enough gold to have a ring or charm made for themselves or a favored girl.

A

A few miles west of Washington, a man may see several small mines, some in operation and some abandoned. great deal of money has been sunk, and it is believed that some has been made. Great areas of gold-bearing rock have been uncovered or blocked out. Gold is obtained, but in many instances it has cost more to extract it than the gold was worth. Every now and then some small capitalist will take over one of the old mines and seek to make it pay.

At present there is one mine in which extensive operations are being carried on; and though the operators do not talk for publication, the belief is general that they are making a good profit from the mine. There are thousands of tons of ore in sight; and if you take a pound of the ore, crush it, and wash it, a fair amount of gold is obtained. Much of the ore assays high, but getting the yellow stuff out in paying quantities is the problem.

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