Figure 68 represents a side view of the lever, or key, A, and its axis at E. R is the platform supporting the standard of the axis; the stationary wires; the battery, G; and the mercury cups, _a, a_ and 10. X is the spiral spring, for the purpose of carrying back the lever, after the finger is taken off and sustaining it in its elevated position. Through the centre of the spiral, passes a rod, with a head upon it at the top of the lever, to limit its upward motion. At its lower end, the rod is secured in the platform, R. 4 and 8 are the two wires supported by the lever, A, and are seen to project down directly over the mercury cups, _a_ and _a_, so that by depressing the key, they both enter the cups and form a metallic connection. The key, B, figure 67, has the same fixtures and is similarly arranged as the key, A, represented above. [Illustration: FIG. 69.] Figure 69 represents a top view of die arrangement of multipliers at the _receiving_ station. R′, R′ and R′; R, R, and R are six magnetic needles, or bars, each of which move freely upon a vertical axis passing through their centres. The lower point of their axes is immersed in cups of mercury, in which also terminate the wires, I, I, I and L, L, L. The wires, D″, A′, B′ and C′, are those coming from the _transmitting_ station. A′, B′ and C′, each enter the needle arrangement, and first passing from left to right, over the magnetic bars, R′, R′ and R′, in the direction of their length, then down and under and round, making many turns, leave these three needles and pass _under_ the needles, R, R and R, and in like manner from right to left round them, making a number of turns, then pass off and unite together, in the wire, 9, which is a continuation of D″. This wire is called the _common communicating wire_,[35] and the wires, A′, B′ and C′ are called _signal wires_. At right angles, there projects from each magnetic bar, a metallic tapered arm, which rests against the studs, V, V, V, V, V, V, when the needle is undisturbed. But when the needles are made to move in the direction, to carry the arms to the left, they are brought in contact with the metallic stops, S, S, S and T, T, T. To each of these stops, it will be observed, a wire is soldered, and continued respectively from S, S, S to ̈1, ̈3, ̈5, and from T, T, T to ̈2, ̈4, ̈6. It will also be observed, that from each of the mercury cups below the magnetic bars, the wires, I and L, and I and L, and I and L, proceed and unite in pairs at, L, L, L; these three united wires are then continued, and the whole are joined in one at 8. The wires, ̈1, ̈2, ̈3, ̈4, ̈5, ̈6, are continued, in a manner hereafter to be described, and are connected with one pole of a battery. The wire, 8, is also continued and connected with the other pole. So that if any one of the needles should be made to move its arm to the left, thereby coming in contact with its metallic stop, the circuit would be