Notwithstanding the many plans which have been proposed for the purpose, there is not yet a single invention which has been brought into use for effecting the much wanted communication between the guards and the engineers.
About twelve months ago, Captain Taylor, R. N. submitted to the Admiralty an instrument for giving signals to steamers and other vessels, which he called a telephone, the sounds from which could be heard for a distance of three miles. This instrument was a modification of an invention, patented a year or two previously, by Mr. C. Hood, F. R. S., which was intended to accomplish the object above proposed, of effecting a communication between the guards and engine-men on railways, and also for marking by signals the track of steam vessels in foggy weather. For both these purposes the invention appears to be perfectly applicable.
The object is accomplished by means of a whistle, similar to that used on the locomotive engines, and worked by compressed air instead of steam. Under the frame of the carriage on which the guard has his seat, is fixed a condensing air pump, worked by a pinion fixed on the carriage axle. The condensed air is received into a vessel holding about two cubic feet; into this vessel the air is pumped until the pressure is about 50 or 60 lbs. on the square inch, when the guard by a motion of his hand or foot throws.the pump out of gear, to be again brought into gear by the same means when required. Connected with this vessel is a pipe, terminating in a whistle, similar to the high pressure steam whistle, but with all the passages made very much finer and smaller. On the fineness of these passages much of the efficiency of the instrument depends, for there being no condensation of steam, as is the case with the steam whistle, the air passes out with extreme rapidity, and without any obstruction. This whistle is placed within a tube in the form of a speaking-trumpet, which is directed towards the engine-man, and by merely turning the handle of the whistle, a powerful sound is produced, precisely similar to the steam whistle, and of an intensity which can be increased to any amount, by increasing the pressure of the air in the receiver.
The advantage of this plan of signals is, that it does not interfere with any of the other arrangements of the train, and is not dependent on any connexion with other parts of the train for its efficient operation.
The object sought to be obtained by Captain Taylor's proposition may we think be obtained by the improved Mouth Whistle, lately invented by Mr. Porteous, of which the annexed cut is a representation. It consists of a combination of any number of metallic tubular whistles, combined under one mouth-piece, and having their tones so arranged, that by the introduction of one discordant note, an extremely shrill vibrating sound is produced, which is conveyed to a great distance; its peculiar discordance enabling it to be distinguished from any other sound.