Britain at Work
A Pictorial Description of Our National Industries

WITH THE RAILWAY SIGNALMEN. 261 which warns the driver, and when the arms drop the detonators are removed. A fog detonator or torpedo is merely a little disc filled with detonating powder and provided with tin straps that are bent down to clasp over the top of the rail. 1 his service, need- less to say, involves considerable danger to the men, and great expense to the com- panies—-the bill for a bad fog will run into many hundreds of pounds. In the neigh- bourhood of London and other large towns it is now usual for signals to have miniature replicas on the ground, so that the men can have the position of the arms on the tall posts above repeated under their noses ; for, otherwise, in a really bad fog a “ fogger would be compelled to climb the post he is guarding to ascertain whether the signal is “ on ” or “ off.” Again, in order to obviate the risks of the men being run over whilst fixing the detonators, one company at least— namely, the Great Eastern—has constructed what are termed fog pits in the permanent way. These pits are long narrow trenches, about five feet deep, between a pair of run- ning tracks, and the miniature repeaters are placed inside them. The foggers are posted in these pits, which are more or less sheltered, and are able to place the detonators on the metals without fear of being run over. There can be no doubt, however, that the fog-signalling problem will never be really mastered until a mechanical device takes the place of human agency. As a matter of fact, patents innumerable have been filed with this object in view. Some of them substitute a mechanical for a human arm in placing a detonator on the rails. For example, there is a magazine detonator ap- paratus connected to a signal lever in such a way that, when the arm is at danger, one deto- nator is carried forward by a plunger, and placed in such a position that it will be exploded by the depression of a hammer near the rail, which hammer is released by the leading pair of loco- motive wheels. If the detonator is exploded another one takes its place at the next movement of the signal lever. When the arm assumes the “ clear ” position, the detonator, if unexploded, is withdrawn to the magazine. An apparatus on this principle is installed on the South- Western Company’s line at Clapham Junc- tion, and works admirably. But the weak point of any such system rests in the fact that the blow struck would be so tremendous that the pedals or triggers thus set would be liable to be easily thrown out of gear. Consequently, several electrical appliances have been devised to surmount this difficulty. For example, there is one the essence of which is the establishment at the side of the track, and along the outer rail, of a magnetic field. An armature attached to the locomotive is then carried through the magnetic field in the close neighbourhood of, but making no actual contact with, the magnets. In the armature there are two independent needles which, being deflected by the electric current, make a contact, and so ring a bell or perform some other operation to call the attention of the men on the footplate. Lastly, there is an electro-pneumatic automatic fog syren. When a signal is at danger, the train on entering the section automatically starts this syren blowing, and the latter continues its warning note till the train arrives at the signal post, with the arin of which it is connected, though, of course, if the signal meanwhile drops to the “ clear ” position the syren ceases to blow. p[. G. Archer. SIGNALLING WITH FLAG.