sufficient to say here that when the train has finished its work at the siding and is ready to go forward, the breakman communicates this by bell signal to the signal-box, and at the same time, by the turning of a button in the front of the instrument at the siding, renews the flow of current, thereby again locking the siding lever and unlocking the signals at the signal-box. The security of the system lies in the fact that, whatever operation takes place at one end, it is only in the hands of the person at the other end to reverse it.
On all the more important main lines the signalmen are enabled to converse one with the other, either by means of the speaking telegraph or of the telephone, which latter is found to be a great acquisition in facilitating the working of the line, more especially through busy station yards.
The mileage of telegraph wires upon the London and North- Western system for purely railway purposes is 11,238 miles, in addition to which there are 6,877 miles of wire appropriated to the use of the Post Office, making up an aggregate of 18,115 miles of wire, while the number of battery cells in work for carrying on the telegraphic business of the Company amounts to 100,323 cells. With such an extent of wires, and so large a number of instruments and batteries in use, it becomes of great importance to provide for a complete and perfect system of maintenance and supervision; but the staff which has to be employed for the purpose is not so extensive as may at first sight appear to be requisite. A line of telegraph has this advantage over a line of railway, that the person charged with the duty of maintaining it in a proper state of repair need not walk from end to end of it in order to detect any fault
