The electric transmission of power is effected by employing the source of power to drive a machine called a dynamo, which generates an electric current.

This current is conveyed by a copper conductor, insulated from the earth, to the distant station, where it passes through a machine called an "electromotor," one part of which is thereby made to revolve, and imparts its motion to the machinery which is to be driven.

This is the simplest arrangement, and is that which is commonly employed when the original currents are not of such high tension as to be dangerous to life in the case of accidental shocks. There is, however, a great waste of power in employing low-tension currents when the distance is great; hence it is becoming a common practice to employ high-tension currents for transmission through the long conductor which connects the two stations, and to convert these into low-tension currents before they reach the houses or workshops where they are to be used. This is done sometimes by employing the high-tension currents to drive a local dynamo which generates low-tension currents.

The discovery that a Gramme machine is reversible - that is to say, when two Gramme machines are coupled together and one is operated as a generator, the other will act as a motor - was an important step taken in the transmission of power. Numerous efforts, since then, have been made to utilize electricity for the transmission of power over a long range. For this purpose the alternating current seems eminently adapted, as transformers only are needed to raise the line to high transmission voltage and to lower it again for use.

The possibilities offered by electrical transmission of water power for sections of country favored with waterfalls are numerous and have been extensively developed, which should result in making them great industrial centers. In this direction much has been done in utilizing the immense power of the Niagara Falls by electrical transmission, works having been built for this purpose both in New York and Canada, and several hundred thousand horse-power developed. The application of the power of waterfalls to the generation of electricity is rapidly extending, and promises to become a great source of mechanical power in the future.