A shows the type as they are arranged on the wheel. The types are square, and move freely in a groove, cut out of the brass type wheel. At 1 and 2 are seen flat brass rings, which are screwed to the wheel, and over the types, confining them to their proper places. Z is a spiral spring, of which there is one to each type, by means of which the type is brought back to its former position, after it is released by the printer. Through each type there is a pin, against which the inner end of the spiral spring rests. The outer end of the spring rests against the circular plate. W represents the wire from the upper helix, soldered to the metallic frame, R′. The two helices of the left hand magnet are joined together, and from the bottom helix the wire proceeds to the lower coil of the right hand magnet. These two helices are likewise connected, and the wire leaves the upper coil at _x_. Thus the wire is continuous from _w_ to _x_. From _x_, the wire is continued to a copper plate, buried in the earth. The frame, R′, being brass, the arbor of the type wheel, and the wheel itself, and each being in metallic contact, they answer as a continuous conductor with the wire, _w_, for the galvanic fluid. The index, _c_, figure 52, is insulated from the frame, N, being made of ivory. There is inserted in the ivory, a metal plate, containing the holes, to which is soldered a wire, _q_, connected with the back coil, K. The two helices being connected, the wire of the front helix comes off at _p_, and from thence is connected with one pole of the battery; from the other pole, it is extended to the distant station, and is there connected with a similar instrument. It will be observed, that the circuit is continuous, except between the type wheel and the metal plate in the ivory. When neither station is at work, the batteries of both are thrown out, and their circuits, retaining in them the magnets of both stations, are closed. For this purpose, there is an instrument at each station, resembling in some respects the pole changer, figures 48, 49 and 50. If one of the stations wish to transmit by reversing his circuit instruments, the battery is instantly brought into the circuit. Through the agency of the clock work and weight, and the pendulum, both instruments are vibrating together, and their type wheels are so adjusted, that when _A type_, of one station, is vertical, the _A type_, of the other station, is also vertical. Now, suppose one station wishes to transmit to the other, the word _Boston_, for example: he first brings his battery in the circuit, then places a metallic pin in the hole of his index, C, marked for the letter B. When the type wheel shall have brought round the pin, corresponding to the type, B, on the wheel, its pin will come in contact with the inserted pin of the index, and instantly the circuit is established. The fluid, passing through the coils of the magnets, on each side of the pendulum, will hold it,