gates are commonly placed in charge of the sig-nal or flagman, who thus combines the functions of a watchman with those of £1. signal-man. Where two grade-crossings happen to be near enough together, the services of one flagman may suffice for both gates or bars, which are operated, the one directly and the other by some connected mechanism. The gates or barriers that guard the grade-crossings vary greatly in construction and mode of operation. In some cases a weighted lever is employed, which is raised and lowered; in others the barrier is made to turn upon a pivot or moves on rollers, or is made of a number of jointed levers that may be projected across the roadway. Some are so devised that they may be operated by a signal-man from a considerable distance. For greater safety, the barrier is often furnished with automatic bell-signals, and, in addition to these safeguards, printed signs of warning are erected at the approaches to the crossings. Figure 16 (pl. 2s) exhibits one of the many devices employed for this purpose.
road is made up of divisions, sections, sub-sections, etc., each of which is under the charge of special officers and employ6s (p. 203), and these divisions, etc., are designated by numbers, letters, and other arbitrary symbols. It is customary to provide mile-stones or iron tablets to indicate the distance from terminal points of the road or front main stations. It is also usual to denote every change of grade by some
convenient method which will show not only the grade, but also the dis tance for which it remains constant.
Trerck-survcillance.—The road is kept under constant surveillance by the trackmen, whose business it is to go over the stretch of road assig,ned to them a certain number of times each day and night; and various meth ods of checking and controlling the inen in the faithful performance of this important duty are in vogue. Oil the Continent of Europe those portions of the road beyond the control of the guards are fenced in, to prevent access thereto of men or animals. Such provision is especially necessary at stations. In the United States, save in a few exceptional cases, and in these only upon limited sections of track, such elaborate provisions for guarding the roadway are not possible, for a number of reasons; the chief among these are that railway companies have not such absolute control over their roadway as is the case in European countries, and that on the score of expense the great length of many of them would preclude such supervision.