Page:Popular Science Monthly Volume 20.djvu/699

Rh when an experiment was tried, to satisfy the French gentleman, we were able to transmit, on a wire between London and Glasgow, no less than 352 words a minute. The growth of telegraphy in this country has been enormous. In 1869 there were only 2,000 offices open, there are now 5,500; there were then only 0,000,000 messages sent a twelvemonth, there are now 30,000,000; the income in 1809 was £700,000, it is now £1,600,000; the number of newspapers and clubs supplied with news was then only 173, it is now 803; and there are 326 towns now being supplied with news direct from London. In regard to submarine cables, I have here a box of specimens of the various types of cable laid down, which is well worth examination. Submarine telegraphy has increased during the ten years, from a few hundred miles of cable, to 70,000 miles, which now engirdles the world. There are many other applications of electricity besides telegraphy, such as, for instance, railway-signals. A railway accident recently occurred at Canonbury, where three or four trains were huddled up in a tunnel. I do not know much about the system of signaling used on that railway, but I know a good deal of the system of signaling in use on the London and Southwestern Railway and other lines. The principle of the "block" system is simply that a railway is supposed to be divided into certain sections of a given length, and no two trains are allowed, or ought to be allowed, to be in one section at the same time. If, for instance, the section be a tunnel, such as at Canonbury, and two trains are allowed on it, the risk of collision is great, as recently proved; but, if the block system be thoroughly and efficiently carried out, there ought to be no such accidents. Some twenty years ago, after a good deal of talking, writing, and persuading, I induced the London and Southwestern Railway to adopt the block system. The system in use on the London and Southwestern Railway is my own. A complete set of apparatus is before you, and I will explain its working. A little semaphore is in front of the instrument, which, when down, indicates that all is clear, and, when up, that there is danger, and the train must stop. Suppose the instrument near me is at Waterloo Station, and the other one near Mr. Goldstone is at Vauxhall. That represents a section of the railway, upon which we want to allow one train only at a time. To ascertain if all is clear at Vauxhall, I send a warning signal of two beats given twice, indicating "A train is coming," which is acknowledged by a signal of one beat from Vauxhall; my semaphore arm is down, telling me that the line is clear, and I let the train go on, sending a signal of two beats [this was done] to Vauxhall, to tell him that the train is in. Vauxhall raises the semaphore behind the train to prevent me from sending on another, and I acknowledge his signal, by giving one beat of the bell. The train is now proceeding; the semaphore arm at this end is up, protecting the train, and I can not, I dare not, send another train until I know that the one now going on has arrived at Vauxhall. It is now