Page:The Working and Management of an English Railway.djvu/92

78 for fitting. The posts are of Baltic timber, varying in size from 9 inches to 15 inches square at the bottom end, and tapering to 6 inches square at the top, the length varying according to circumstances. About seven feet of each post, at the bottom, is left the full size of the timber from which the post is cut, and this portion is first charred in a furnace and afterwards well coated with gas tar, while upon the top of the post is placed a galvanised cast-iron cap. The arm of the signal is formed of a thin steel plate, stiffened by two corrugations running lengthways, and is riveted to a galvanised cast-iron centre, upon which is fixed an adjustable frame for the spectacle-glasses, made sufficiently heavy to counterbalance any accumulation of snow on the arm, and keep it in its "danger" position should any of the fittings fail. The arm works on a spindle squared to receive it at one end, and on the back light lever at the other end, except when the signal is electrically repeated, in which case a racked segment is substituted for the back light lever, and it is geared with a similar segment, in connection with the electrical contacts of the repeater apparatus. The spindle turns in a casting fastened to the post by four ⅝-inch bolts, which also serve to secure the lamp bracket fixed at the back of the arm, this bracket being of sufficient width to form a "stop" for the arm when in its "danger position."

There are several other distinctive patterns of signals employed for special purposes, amongst them being the "disc" signals, previously mentioned, for controlling the exits from sidings, and the miniature semaphore signals placed low down on the post, which at certain busy parts of the line are used instead of a hand signal when it