A torpedo is a square piece of basically black powder wrapped in a heavy water proof paper with a flexable metal strap built in to it. They are used to signal trains ( either approaching or following sections) of a train stopped ahead. This was what the one time flagman and head brakeman did. If their train had to stop unexpectedly then they would grab some torpedos, fussees and red flags or lanterns and head out in front of and to the rear of the train. The Timetable for the district specified how far but was usually around the two mile mark. When they got there they strapped two torpedos to the rail, no more than 100 feet apart and no closer than 50 feet apart. They could then return 1/2 the distance to their train and wait and wait and wait until they either stopped the next train or were recalled by a whistle signal from the engineer. When a train or engine runs over the torpedos and it is said in stories that they are equal to about 1/4 stick of dynamite, the rules state that they will immediately reduce to restricted speed and remain at restricted speed until stopped by a flagman or for a distance of two miles. The explosion of one torpedo means the same as two but the use of two is required. This of course was back in the days when trains ran by timetable authority but every engine is still supplied with them and the rules are still in the book in case of a major signal system failure or some other emergency that could cause the superintendent to suspend the signal system.
By the way, Restricted speed is: a speed that will permit stopping within one half the range of vision, short of train, obstruction, switch not properly lined, looking out for a broken rail etc but not exceeding 15 MPH. In other words, if it is foggy as hell and you can only see fifty feet, you had better be able to stop that 26,000 ton coal train with 25 feet or you are going too fast. I have seen lots of trains creeping along at 2-3 mph in heavy fogs while operating at restricted speed for some reason or other.
Mike
