Fig. 70.
TransmittingPart of Receiving
Station.Station.
The wires, D″, A′, B′ and C′, are detached from their corresponding wires of the transmitting station, and it may be imagined that many miles of wire intervene and connect the two. In the left hand [figure], those mercury cups above and below, 1 and 10, are joined by two wires passing through a moving lever, in the same manner as has been described in [figure 67]. We will, therefore, call the key, carrying these two connecting wires, H. In like manner the key for the cups above and below the numbers, 2 and 20, is called J; for 3 and 30, is K; for 4 and 40, is M; for 5 and 50 is O; for 6 and 60, is U. The key which connects the two mercury cups on the right and left of number 7, of the wire, D″, is called 7. There are 7 keys; two for each battery, 1′, 2′ and 3′, and each wire, A′, B′ and C′; and one for the common wire, D″.
It will now appear, that if the key, U and 7, are depressed, the cups above and below, numbers 6 and 60; and the cups on each side of number 7, will be connected together so that the current leaving, P, or the positive pole of the battery, 3′, goes to the lower cup, 50; then by the stationary cross wire to upper cup, 6; then passes to lower cup, 6, by the wire supported by the lever, U, which is now pressed down, and its ends immersed in the two cups; then along the wire, D, to the left hand cup, 7; then to the right hand cup, 7, by the wire supported by the lever, 7, and which is immersed in the two cups; then through the extended wire to D″, of the receiving station; then through 9, to the two multiplying coils of the wire, C′, deflecting the arm of the needle, R, to the right, against the stop, V; and the arm of the needle, R′, to the left against the metallic stop, S, as indicated by the arrow at S; then along the extended wire, back to the lower cup, 60, of the transmitting station; then to upper cup, 60, through the wire supported by the lever, U; then to N, the negative pole of the battery, 3′.
It will be observed of the two needles, R and R′, in the circuit of the same wire, C′, that if R is deflected to the right against the stop, V, then R′ will be deflected to the left against the metallic stop, S. The current, to produce these deflections, being through the wire C′, in the contrary direction to that indicated by the arrow of the wire, C′. But if R is deflected to the left against the metallic stop, T, then R′ will be deflected to the right against the stop, V. The current to produce these deflections, will then be through the wire, C′, in the direction of the arrow of that wire. The same effect is produced upon the two other pairs of needles of the wires, A′ and also B′. These contrary movements of the two needles, when a current is passing, are produced by the coils being so wound, ([see figure 69],) that the wire passes round one needle in a contrary direction to what it does round the other.
If, now, we depress the keys, O and 7, the cups above and below, 5 and 50, and on each side of number 7, will be connected. The fluid will then pass from P or positive pole of the battery, 3′, to the lower cup, 50; then through the key wire to upper cup, 50; then along the extended wire, C′ to the receiving station; then through the coils of the multipliers, deflecting the arm of the needle, R, to the left against the metallic stop, T; and the arm of the needle, R′, to the right against the stop, V, as indicated by the arrow at V; then to wire, 9 and D″; then along the extended wire back to the transmitting station, to the right hand cup, 7; then by the key wire to the left hand cup, 7; then to wire, D; then to upper cup, 5; and through the key wire to lower cup, 5; then by the cross wire to upper cup, 60, and then to N, or negative pole of the battery.
We have now shown the route of the current, when the keys, U and 7; and the keys, O and 7, were depressed. It will be observed, that when the keys, U and 7 were used, the current through the wire, D″, was from left to right; and when the keys, O and 7, were used, the current was from right to left. Thus, by means of the six keys, the current of each battery may be made to pass in either direction through the common communicating wire, D″. By the keys, U, M, J, with 7, the current is made to pass from left to right along the wire, D″. By the keys, O, K, H, with 7, the current is made to pass from right to left along the wire, D″. By these six keys, all those various deflections of the six needles are produced, which are necessary to close the circuit of such of the wires, ̈1, ̈2, ̈3, ̈4, ̈5, ̈6, with the wire, 8, as are required for marking the signals desired, on an instrument now to be described.