472
EXPOSITION AT VIENNA.
section two” of the preceding one, or to " proceed, keeping a sharp look-out” for it to the next station, and "wait for orders.” This at once introduces all the danger and uncertainty of the English time system.
I do not wish to disparage the manner in which the train- despatching system is conducted. Where skilled American telegraphers are employed and properly remunerated, they do their work better than any others in the world. Such men cannot be had for railway service, however, in sufficient numbers to allow a telegraph office at every point where the block system would establish a signal, and a large traffic cannot, therefore, be worked with safety by " train despatching.” Were a simpler telegraph employed for the ordinary service, the block system adopted for the running of trains, and each worked by railway employés, economy and safety would, probably, both be advanced by the change.
Various forms of the block are in use in England on the different railways, none of which are on exhibition at Vienna. From the simple needle to the most complicated apparatus, however, the instruments in use have merely one purpose,— that of sending a signal from one signal-station to the man in charge at the next, who controls the movement of the semaphore.
The system of Mr. Preece, which is adopted by the Metropolitan Railway, comprises three wires, two of which are employed for the block-signals proper, one for each line of rails, and one for movement-signals (see class 1) and acknowledgment of the block-signals. On the third wire a " bell- sounder” is employed, with a code to indicate the character of approaching trains, etc.
The apparatus is shown at Plate XIII. as working between Barnes and Putney. The semaphore and switch-lever (Fig.‘ A) are miniature copies of those used for out-door signals worked by hand. They are inclosed in a box or placed on the counter in the signal-house at each station.
There are, according to Mr. Preece, two fundamental requirements of the system : one being that the signal-man at one station shall have " sole and complete control ” of the semaphore at the other; the other being that "every signal shall be properly acknowledged, and that the acknowledgment