60 MODERN SCIENCE READER 



person who first discovered it. The ferrite makes the rail 

 tough to resist fracture, and the pearlite is the part of the 

 metal which contains the carbon and which makes the rail 

 hard and stronger than iron and enables it to wear well 

 under the friction of the car wheels. The metallurgist at 

 a glance knows this to be the normal structure of a good 

 steel rail such as daily and hourly fulfils its duty all over 

 the world. 



But let us return to the rail which broke, which could 

 not stand the speed of the express train. This rail out- 

 wardly had the appearance of respectability; the section 

 boss had tested it with his sledge many times ; it had held 

 up bravely under many a train; but suddenly it "went 

 bad." 



A good steel rail on the open road will stand at least ten 

 years of active service, years during which the swiftest 

 passenger trains with the heaviest of all cars, the "Pull- 

 mans," go pounding across the joints. The freight trains 

 with their more ponderous engines and more heavily loaded 

 cars seldom break a rail, on account of their much slower 

 rate of speed ; for the ordinary steel rail, good or bad, will 

 sustain ten times the load put upon it if this be applied 

 slowly; but the high speed of the heavy passenger train is 

 apt to make the bad rail succumb to the sudden shock of 

 the gigantic monster which hammers down upon it. 



The rail which is put in a critical place, as for example 

 on a very sharp curve, is seldom found wanting, for the 

 very reason that only the best selected stock is used for 

 such a locality, and a dangerous curve is always assidu- 

 ously watched by the section man and the division super- 

 intendent. 



The faulty rail, however, on the straight track, which 

 got slipped in with the good ones, is the one to be dreaded, 

 for after leaving the mill there is no possible way to 

 distinguish this physically incompetent piece of steel from 

 its good neighbors. 



For a better understanding of some of the imperfections 



