lustrations may be found in electric railways,
and where water power can be obtained as the primal source of energy,
the cost is not excessive. It is found, however, that even with the most
improved forms of mechanism, in electrical construction, the internal
combustion engines are far more economical.

_Transmission of Energy_

One of the great problems has been the transmission of the current to
great distances. By using a high voltage it may be sent hundreds of
miles, but to use a current of that character in the cars, or shops, or
homes, would be exceedingly dangerous.

To meet this requirement transformers have been devised, which will take
a current of very high voltage, and deliver a current of low tension,
and capable of being used anywhere with the ordinary motors.

THE TRANSFORMER.--This is an electrical device made up of a core or
cores of thin sheet metal, around which is wound sets of insulated
wires, one set being designed to receive the high voltage, and the other
set to put out the low voltage, as described in a former chapter.

These may be made where the original output is a very high voltage, so
that they will be stepped down, first from one voltage to a lower, and
then from that to the next lower stage. This is called the "Step down"
transformer, and is now used over the entire world, where large voltages
are generated.

ELECTRIC FURNACES.--The most important development of electricity in the
direction of heat is its use in furnaces. As before stated, an intense
heat is capable of being generated by the electric current, so that it
becomes the great agent to use for the treatment of refractory material.

In furnaces of this kind the electric arc is the mechanical form used to
produce the great heat, the only difference being in the size of the
apparatus. The electric furnace is simply an immense form of arc light,
capable of taking a high voltage, and such an arc is enclosed within a
suitable oven of refractory material, which still further conserves the
heat.

WELDING BY ELECTRICITY.--The next step is to use the high heat thus
capable of being produced, to fuse metals so that they may be welded
together. It is a difficult matter to unite two large pieces of metal by
the forging method, because the highest heat is required, owing to their
bulk, and in addition immense hammers, weighing tons, must be employed.

Electric welding offers a simple and easy method of accomplishing the
result, a