464
EXPOSITION AT VIENNA.
is occasioned.* The danger arising from derangement of apparatus is to a greater or less extent inherent in any system.
I am indebted to the Allgemeine Telegraplienbau-gesell- schaft, of Vienna, for a drawing of the apparatus of Mr. Schonbach, an engineer on the Westbahn, by which railway the system is employed and exhibited.
The construction is identical with that of the system Hohenegger, with this exception, that the upright lever, instead of raising and lowering a semaphore arm, is used to turn a wheel with a toothed axle. The teeth of the latter fit into the cogs of a horizontal wheel, the axle of which is extended upwards and attached to a circular disc, which it turns half round whenever the clock-work is released by the magnet.
Herr Ritter von Bergmiiller, of Vienna, exhibits a third signal of this class, which is of much cheaper construction than the others, the clockwork being all of iron. The armature moves horizontally between the two poles of the electromagnet, releasing a series of catches controlling the clockwork, which turns the disc of the semaphore. The winding apparatus is in the same position as in the Hohenegger and Schonbach systems, but the weight descends several feet below the ground, giving it a fall of perhaps six feet. Herr von Bergmiiller states that seven signals can be given for every inch of the weight’s descent, so that it needs to be wound up once for every five hundred signals.
In 1866 , Mr. Thomas Hall devised a method of connecting an electric circuit with a switch or drawbridge in such a manner that when the rails of the track were displaced the circuit would be closed thereby and a danger-signal shown by means of a semaphore, operated by an electro-magnet, while at the same time a continuous alarm would be sounded
* In bell signals, on which a code is used, the danger of atmospheric electricity imitating or changing the signals is very slight; where the trembling-sounder is employed, a continuous ringing cannot be produced; and where a signal is given by and the “ control ” returned to a train in motion, as might be done by combining the automatic whistle with any of the systems in Group II. b, the intervention of lightning at the moment of receiving the “ controlis exceedingly improbable. If in all of these cases, however, delay only and not danger is occasioned, its rare occurrence would be more than compensated by the saving in wires.