Every wireless station, whether on ship or on shore, has a separate call-signal, consisting of three letters. For instance, Clifden is MFT, Poldhu MPD, Norddeich KAV, s.s. _Lusitania_ MFA, and H.M.S. _Dreadnought_ BAU. Glace Bay, GB, and the Eiffel Tower, FL, have two letters only. In order to avoid confusion, different countries have different combinations of letters assigned to them exclusively, and these are allotted to the various ship and shore stations. For example, Great Britain has all combinations beginning with B, G, and M; France all combinations beginning with F, and also the combinations UAA to UMZ; while the United States is entitled to use all combinations beginning with N and W, and the combinations KIA to KZZ. There are also special signals to indicate nationality, for use by ships, British being indicated by - - -- -, Japanese by -- - -- -, and so on. Wireless telegraphy apparently has a useful future in railway work. In spite of the great perfection of present-day railway signalling, no railway company is able to avoid occasional accidents. Some of these accidents are due to circumstances which no precautions can guard against entirely, such, for instance, as the sudden breakage of some portion of the mechanism of the train itself. In many cases, however, the accident is caused by some oversight on the part of the signalman or the engine-driver. Probably the great majority of such accidents are not due to real carelessness or inattention to duty, but to unaccountable freaks of the brain, through which some little detail, never before forgotten, is overlooked completely until too late. We all are liable to these curious mental lapses, but happily in most cases these do not lead to disaster of any kind. The ever-present possibility of accidents brought about in this way is recognized fully by railway authorities, and every effort is made to devise mechanism which will safeguard a train in case of failure of the human element. The great weakness of the ordinary railway system is that there is no reliable means of communicating with the driver of a train except by the fixed signals, so that when a train has passed one set of signals it is generally beyond the reach of a message until it arrives at the next set. On the enterprising Lackawanna Railroad, in the United States, an attempt has been made to remove this defect by means of wireless telegraphy, and the experiment has been remarkably successful. Wireless communication between moving passenger trains and certain stations along the route has been established, and the system is being rapidly developed.