Fig. 78.
[Figure 78] represents a top view of the coil and magnets of Mr. Bain’s machine. B is the compound permanent magnet, with six bars. N is the north pole, and S the south pole. A, A are the sides of the brass frame containing the coils; C, C are the spiral springs on each side: a and a is the axis of the coil: o, o, is a part of the frame containing the clock work, (not shown in this [figure],) supporting one centre of the coil, and I and I a support for the other centre. N and P are the wires, one of which is in connection with the ground, and the other with the extended wire. When the circuit is closed, and the current from P pole of the battery is in the direction of the arrow above, and then through the coil to the other pole, N, in the direction of the arrow below; the end, D, of the coil, will be depressed, and the end, U, will rise; reverse the current and the effect is the elevation of the end, D, of the coil, and the depression of the end, U.
Wheatstone’s Rotating Disc Telegraph,
invented, 1841.
[Figure 79] represents that portion of the instrument which belongs to the transmitting station, of which, K, is a circular disc, with the alphabet and numerals, marked in two concentric circles upon it: a are handles projecting from its rim, one to every letter, by means of which, the disc is turned upon its axis, and brought to that position, b, required for signalizing a letter. O is a side view of the disc, K: t is the rim of the disc, with its holders: h is a portion of the axis of the disc, shown as broken off: c represents a silver band surrounding a pulley, or hub, upon the axis, and directly behind the disc. Upon the hub are metallic ribs, b, parallel with its axis, corresponding in number to the letters on the dial. Each rib forms a metallic contact with the silver band, c, and are separated from each other by pieces of ivory, fastened to the hub. Both the ribs and ivory pieces are made perfectly smooth and even upon their surface: e is a metallic spring with a portion of it pressing against that portion of the hub between the silver band, c, and the disc, t, in such a manner that when the disc is turned, the metallic ribs and ivory pieces shall alternately come in contact with it. To this spring is soldered a wire connected with one pole of the battery, g, and from the other pole proceeds the wire, n: d is another metallic spring, similar to e, but pressing only upon the silver band, with which it is always in contact, and to which a wire, p, is soldered. Whenever the spring, e, is in contact with any of the metallic ribs, there is a continuous connection from n to p, viz. from p, to the spring in contact with the silver band, c, thence to the rib with which the spring, e, is in contact; then to the spring, e, then to the battery, g, and then to the wire, n. If, however, the disc, O, should be turned, so that the spring, e, is in contact with the ivory, then the circuit is broken at that point, and in this manner the circuit is alternately broken and closed as the wheel, O, is turned from one letter to another by means of the handles at t.
Fig. 79.
