456
EXPOSITION AT VIENNA.
production of force which is necessary to actuate with any degree of certainty our exposed signals. We are, therefore, compelled to adopt the nearest approach to this, and to rely upon small electrical instruments, which direct the signalman how to exhibit his out-door signals by displaying the signals which they themselves ought to give.”
Since the date of the above, the difficulties alluded to have been ingeniously overcome by several inventors. In the number of apparatus the Austrians, so far as I know, have taken the lead. They have, in fact, the only instruments of this class at the Exhibition. It is only recently that electrical signals for such purposes have been permitted in Austria. There are now, however, two systems in operation, and a third is completed and shown at the Exposition.
The first of these is that of Mr. Ilolienegger, an engineer of the Nordwestbahn, by which company the signal is exhibited and employed. It is also used on some roads in Hungary.
I am indebted to Mr. Ilolienegger for a diagram of the apparatus which is shown in Plate IX. The machinery is in many respects similar to that of the system Leopolder, page 441, but its adaptation is so different and so interesting that it merits a separate description.
Plate IX. A shows the external appearance of the semaphore, looking down the line; B, page 458, the internal apparatus, and C the connection to the station.
The arm of the semaphore moves through an arc of forty- five degrees, and carries on its left extremity a smaller arm, in which are set two circular pieces of glass, one red and the other green, which pass in front of a fixed lantern, accordingly as the arm is raised or lowered. The lamp is raised to its position by means of a chain shown in the figure. At night, therefore, a red light signifies that the line is clear, and a green one that it is blocked.
The source of electricity is a magneto-electric or induction apparatus (Plate C), which is placed at the station. The slightest turn of the crank produces a sufficient current to operate the semaphore. To prevent accidental signals, therefore, the circuit is broken at a, and it is necessary to depress the button a (which is set even with the surface of a