The capitalization in electrical appliances in the United States in 1898 is estimated at $1,900,000,000, most of which is devoted to industries in which the electric motor is used. The export of electrical apparatus from this country amounts to more than three million dollars annually, and it is said that there are eight times as many electric railways in the United States as in all the rest of the world combined. The use of electrical current in twelve principal cities in the United States was distributed in 1898 as follows: Lamps, arcs, and motors in sixteen candle power equivalents. Boston 616,000 New York 1,718,000 Chicago 1,278,000 Brooklyn 322,000 Baltimore 224,000 Philadelphia 488,000 St. Louis 303,000 San Francisco 231,000 Buffalo 125,000 Rochester 184,000 Cincinnati 201,000 New Orleans 81,000 Boston makes the largest use of electrical current in proportion to its population of any city in the world. Rochester is next. Both of these cities employ in electrical units of 16 c. p. equivalents, more than one electric lamp for every man, woman and child in their respective populations. The dynamo and the electric motor have together wrought this great development. The dynamo takes mechanical power and converts it into electrical energy, and the electric motor takes the electrical energy and converts it back into mechanical power. Standing behind them both, however, is the steam engine, and these three afford a beautiful illustration of the law of correlation of forces. The force starts with the combustion of coal under the boiler of the steam engine. When carbon unites chemically with oxygen, it is an exothermic reaction that gives off heat as correlated energy. The influence of heat on the molecules of water in the boiler causes them, by repellent action, to assume the qualities of an elastic gas, and this expanding as steam drives the piston of the steam engine. The steam engine overcomes by force the resistance existing between the dynamo’s field magnets and armature coil, and sets up in the latter the correlated force of an electric current, and the electric current, traveling to its remote destination by suitable conductors, enters the coils of the electric motor in reverse relation to that of the dynamo, and in producing the reverse effect between the armature and field magnets, electrical energy is converted back into mechanical power. It is not possible to obtain in the electric motor the full equivalent of the dynamo’s current, nor in the dynamo the full equivalent of the steam engine’s power, nor in the steam engine the full equivalent of the chemical energy in the combustion of coal. Loss by radiation, by conduction, by friction, and by electrical resistance precludes this, but while there is loss in a