RAILWAY CONSTRUCTION. 335 



the arrangements are generally carried out somewhat in the 

 following manner. During the prevalence of a fog or snowstorm, 

 a fog signal-man is placed near each of the signal-posts to be 

 protected, and is supplied with a hand signal-lamp, hand-flags, 

 and a packet of detonators. So long as the arm of the signal-post 

 at which he is alongside stands at danger, he must keep two de- 

 tonators on the rail of that line which the signal controls, and also 

 show a RED hand-signal (hand-flag by day, and hand-lamp after 

 dark) to the approaching train. When the signal arm is lowered 

 to show that the line is clear for the passage of the train, the fog 

 signalman must remove the two detonators, and show a GREEN 

 hand-signal (flag, or lamp) to the approaching train. When an 

 engine driver hears the report of a detonator crushed by his 

 engine, it is his duty to shut off steam immediately, and bring 

 his engine to a stand, after which he must proceed very cautiously, 

 until he receives further signals by hand or otherwise, or receives 

 the line-clear signal to continue on his journey. Detonators are 

 also of great service both in fine or bad weather, in cases of a 

 wash away, a failure of works, or obstruction on the line, when 

 a hand-signal may not be seen, but a detonator must be heard. 



Mechanical Gates. Mechanical gates, worked and controlled 

 from the inside of a signal- cabin, are now very largely adopted 

 for public road level-crossings instead of ordinary hand-gates, 

 opened and closed by a gateman walking from side to side of the 

 line across the rails. Being worked from inside the cabin, they 

 remove all possibility of the gateman being struck by a passing 

 train ; they move simultaneously, and can be opened or closed in 

 very much less time than hand-worked gates, which have to be 

 moved one by one, and being interlocked with the signals, the 

 mechanical gates cannot be placed across the lines of rails until 

 the train-signals in each direction are set at danger. When 

 set for either train traffic or public road traffic, the gates are held 

 firmly in position by metal stops, rising out of cast-iron boxes 

 lying flush with the ground, and worked by a separate lever in 

 the signal-cabin. 



Assuming the gates to be set for train traffic, and it is 

 desired to open them for the public road traffic, the first opera- 

 tion will be to pull over the levers, and raise the signals in each 

 direction to danger, and thus release the stop-lever, which can 

 then be pulled over, to lower the gate-stops and allow the gate- 

 winch to be turned, and the gates moved round into correct 



