Thus Henry produced the electromagnet which was the beginning of the mastery by man of the subtle fluid.

The possibility of utilizing Professor Henry's electromagnet for the purpose of transmitting intelligence to a distant point was conceived by still another American, Professor Samuel Finley Breese Morse, of New York, [Footnote: He was born in Charlestown, Massachusetts, April 27, 1791.ED.]

[objects which attract by physical force] lodestone, loadstone, lodestar, loadstar^; magnet, permanent magnet, siderite, magnetite; electromagnet; magnetic coil, voice coil; magnetic dipole; motor coil, rotor, stator.

In 1832, he conceived the idea of a true electric telegrapha writing at a distance by means of the electromagnet.

Every telephone receiver and transmitter has a mouth-and ear-piece to receive or throw out the sound, a thin round sheet of lacquered metalcalled a diaphragm, and an electromagnet; together they reproduce human speech.

The principle of this instrument is the same as that of the old Kelvin instrument; the clockwork attached to it unrolls a strip of paper wound on a roller; at intervals the needle of the instrument is depressed by an electromagnet and makes a dot on the moving paper.

the mutual force systems required to hold at rest two electromagnets fulfilling the following specification: The two electro magnets are to be of the same shape and size as the two bodies, and to be placed in the same relative positions, and to consist of infinitely thin layers of electric currents in the surfaces of solids possessing extreme diamagnetic qualityin other words, infinitely small permeability.

This dial carries two insulated studs, p, each electrically connected with one terminal of the coils of an electromagnet, K, whose other terminal is connected to the other pole of the battery.

Should the torpedo however deviate from this course, the needle makes contact with one or other of the studs according to the direction in which the deviation takes place, and completes the circuit through the corresponding electromagnet, which attracts the armature and causes the disk to move, so as to diminish the supply of water to one motor and increase it to the other, and so cause the torpedo to again assume the required direction.