REPORT OF MR. HOWE ON RAILWAY SWITCHES, ETC. 497
make the details plain. There is also a long flat bar, H, of wrought iron, held alongside of the rail, supported by short links, which move around studs fastened to the lower part of the rail. These permit the motion of the bar through an arc indicated by the dotted lines. A rod, L, joins this bar to one of the bell-cranks of the locking apparatus, so that the motions of the fastening bolt must be isochronous with those of the bar. When the links stand vertically, the bar is parallel to the surface of the rail, and about ^ of an inch below it. In the drawing, the fastening bolt is withdrawn. When the "switch-lock lever” is drawn, the fastening bolt will be inserted, and at the same time the bar will rotate into the position denoted by the dotted lines. If, now, a train pass over, the rims of the car-wheels will rest on this bar and hold it down, so that, as long as there is a wheel on the rail above the bar, the bolt cannot be withdrawn, and consequently the switch cannot be shifted.
This contrivance is rapidly coming into use on English roads, where some such arrangements are required by law on new lines. The bar need only be as long as the longest distance between two car-wheels. With their short cars, this does not make an inconvenient length. To extend between the trucks of our long cars, would require a cumbersome bar, and it would be only with great difficulty kept clear from dirt and snow, since there is no ready way of covering it. However, if this appendage be deemed impracticable, the locking apparatus proper could be used, since it adds an element of security, and is simple, practical, and not likely to get out of repair.
At the Cannon-street station, in London, perhaps, there is a greater complication, arising from the number of trains and the narrow space in which the tracks are located, than at any other similar place in the world. The following description is taken from the London Engineer. It needs only to be explained that the "points” or "facing points” correspond to our switches.
“ The lines from London Bridge and from Charing Cross take circular sweeps which bring them to a junction near the Borough Market. The lines so joined, as well as others parallel to them, run 63