REPORT OF MR. ROBERT B. LINES.
479
on the second track for B, the agent at A, instead of pressing M 1 to advise B of -its departure, which would throw the needles d and y 1 to "free,” presses the button M, towards which the needle d is now inclined as in the case before described it was inclined towards M 1 .
. It is not necessary to repeat the rules adopted for the entire system of signalling, which are the same as in any "block” system. To carry them into effect on the apparatus, the following special directions are given :
1. To signal the departure of a train, press upon the button towards which is inclined the needle of the " right track.”
2. To acknowledge this signal, press upon the button under the indication "occupied.”
3. To announce the arrival of a train, press upon the button under the indication "free.”
The two instruments necessary for intermediary stations are generally inclosed in one box, as shown in the cut.
The system of Mr. Tyer, in a telegraphic point of view, is very ingenious and possesses the great advantage of requiring but one wire. Like Mr. Preece’s system, each signal requires the concurrence of the agents at both stations before it is completed. There is, therefore, very little danger from atmospheric electricity. Unlike Mr. Preece’s system, that of Mr. Tyer does not give the man at one station "sole and complete control” of the indicator at the other. But the control spoken of by Mr. Preece is only electrical, and might easily be overcome by mechanical means. It being suggested that the signal-man might "tie down the arm of the semaphore with a string,” Air. Preece very aptly replied that he might also "neglect his duty, disregard his signals, and swear that the semaphore was down when it was really up.”
In the Tyer system a signal-man to change his own signal must also change that of his neighbor, and this is probably as good a control as putting it out of his power to interfere electrically with his own indicator.
The new system of Messrs. Siemens & Halske, exhibited both in the German and English departments at Vienna, goes a step farther towards the control of the signal-man than either the Preece or Tyer system. By the kindness of Dr.