316 RAILWAY CONSTRUCTION. 



the switches being moved again until the entire train has passed 

 over them. A set of switches may be carefully made and work 

 well, but it is quite possible for some fracture or obstruction, to 

 intervene and prevent them closing properly. If a train or 

 engine were passing through them in a trailing direction, as 

 indicated in Fig. 345, the wheels would most probably force the 

 sliding-rail home, and no disturbance would arise. If, however, 

 the train were coming in the opposite or facing direction, the 

 chances are that some of the wheels would take one road and 

 some the other, and cause a derailment. The same casualty 

 would occur if the switches were moved during the passage of 

 the train. 



To guard against the above contingencies, the facing-point 

 bolt-lock and rocking-bar have been introduced. The system is 

 applied in various forms, but the arrangement shown in Fig. 480 

 will explain the principle generally. 



A strong casting, A, is securely bolted to the top of the sleeper 

 carrying the chairs on which rest the point ends of the sliding, 

 rails. This casting has an internal groove or chamber formed for 

 its entire length from C to D, as indicated by the dotted lines, 

 and in which slides the locking-bolt B. The point ends of the 

 switch or sliding-rails are connected by the transverse rod E, 

 which is forged into a vertical bar form for that portion of its 

 length, which passes through the opening, F, prepared for it in 

 the casting A. In this vertical bar a hole or slot is cut to corre- 

 spond to the exact size of the locking-bolt B, and at a distance 

 to suit the sliding-rails when pulled over to their properly closed 

 position. This locking-bolt, B, will not pass through the hole in 

 the vertical bar until the sliding-rails are quite close home, and 

 when once through the hole the sliding-rails cannot be moved 

 until the locking-bar is withdrawn. In some cases two holes or 

 slots are cut in the vertical bar to enable the points to be bolt- 

 locked for both directions. 



The rocking-bar is designed to prevent the withdrawal of the 

 locking-bolt before all the vehicles have passed over the points. 



This rocking-bar consists of an angle iron or tee-iron bar of 

 a length equal to the longest wheel-base of the rolling-stock, and 

 is carried on short pivoted arms working in cast-iron or 

 wrought-iron brackets secured to the rails as shown in Fig. 481. 

 The pivoted arms have a movement backward or forward, and 

 when at either the one or the other extremity, the upper surface 



