number of devices have been made for the purpose of regulating motors on these circuits. One arrangement for this purpose is that employed in the Crocker-Wheeler motor. It consists of a gramme ring armature revolving in a stationary field magnet and provided with a governor attached to the shaft within the pulley of the machine. When the speed of the motor reaches the proper limit, the governor draws the armature lengthwise out of the field, thereby weakening the power, and keeping the machine running at constant speed under any variation of the work required of the motor. See the Electric Motor and its Applications, Martin and Wetzler; Dynamo-Electric Machines, S. P. Thompson.

ELECTRIC ORGAN. Electricity is used in two ways in operating organs-for pumping and for operating the valves leading to the various sounding tubes in accordance with the manipulations of the key-board. In many places, especially in large churches having complicated organs, a part of the organ tubes are at such distance from the key-board as to preclude the air being admitted to them and shut off quickly as is required in playing, by any mechanical means which can be actuated by the weak force with which the organist depresses the keys. To meet this difficulty, the agency of electricity has been invoked, and now in all large organs the connection from tubes to keyboard is made in this way: The valve admitting the air to the sounding tube is controlled by an electro-magnet. This magnet is connected by a wire to the key-board, and is led to a contact point on the under side of the key corresponding to this tube. The wire is also connected to a suitable battery which supplies the current when this key is depressed, and also supplies the wires leading from all the other keys to the other tubes. When the keys are depressed by the organist the magnets throw open the air valves, and the corresponding notes are sounded without effort of the operator. The application for pumping air for organs is made by the use of an ordinary electric motor (q.v.), the motor being connected to an electric light circuit to draw its supply of clectricity and geared to the bellows of the organ, so as to operate the latter.

ELECTRIC RAILWAYS. One of the most important applications of electricity, and the most important of its applications to the transmission of power, is its use for propelling cars. This use is being rapidly developed at present. The value of the plan depends upon the fact that large amounts of power, after being converted into electricity, may be carried through the rails of the track or through convenient conductors overhead to the moving cars, and there readily converted without trouble into the power necessary for driving the cars. This conversion is effected through the agency of electric motors (q.v.), which are small, clean, noiseless, and easily handled, and are therefore to be preferred to either dummy engines or horses. The generation of electricity at the central station and its reconversion of power at the car can be accomplished with the loss of less than 40 per cent. of the power supplied at the station. So the system of carrying the power to the car is sufficiently efficient to permit of great saving by generating all of the power at one place by a very good engine instead of by a number of poorer and less efficient engines on the cars, which are invariably several times more expensive, or by the use of horses, which are still more expensive. The full-page illustration shows a station fitted with Edison dynamos (see MAGNETO-ELECTRIC MACHINES) driven by high-speed Armington and Sims engines. It may be mentioned that the station illustrated is also adapted to supplying electric lights. The current generated at this station is led out to the cars by suitable conductors. In the particular place chosen as an illustration-the city of Richmond, Va.—where the entire street-car lines of the city are run by electricity, the currents are carried out from the station upon overhead conductors. These conductors are run parallel with the tracks, and are suspended a few feet above the cars. The connec tion from the conductor to the motor in the car is made by a flexible arm projecting up from the top of the car, very much like a fishing pole, carrying on its end a roller or trolley which presses upward against the conductor. The current passes from the conductor to this roller, and down the rod to the roof of the car; thence by a wire to the motor and to the car wheels, and returns by the rails to the station. The motor is connected by suitable gearing to the wheels of the car. The speed of the car is regulated by proper controlling switches governing the power of the motor. The introduction of electric motors for running street cars has progressed very rapidly.

ELECTRO-CAUTERY. By means of a heated platinum wire, parts of the body may be safely cauterized which could not be reached by a red-hot iron. The removal of tumors may be effected by drawing a loop of platinum wire round their base, which is then gradually pulled together. It has been observed that when the temperature of the wire is about 600° C., the combustion of the tissues is so complete that there is no hemorrhage; while at 1500° the action of the wire is like that of a sharp knife.

ELECTRO-CHEMICAL ORDER OF THE ELEMENTS. When two metals are placed in contact and immersed in a solution capable of acting on one of them, an electric current is produced, positive electricity passing from the metal acted on, through the liquid, to the metal unacted on. The former metal is said to be electro-positive to the latter. By experimenting with different pairs, we can arrange the metals in electro-chemical order. This order depends upon the readiness with which the metals are acted upon by the solution, and is not the same for all solutions.

The following is the electro-chemical order of the more common metals, the liquid