THE ANATOMY OF A STEEL RAIL 



63 



cause a fracture from a sudden shock when the metal is 

 cold. Therefore phosphorus and sulphur are the evil asso- 

 ciates which a steel rail must be as free from as possible 

 to be'classed as good. 



FIG. 5. ETCHED SECTION OF A BAD BAIL, SHOWING THE "PIPE." 

 (THE LIGHT AREA is THE EEVEALED "PIPE") 



So, you see, if no more than the ' ' pipe ' ' be removed, the 

 segregation of impurities at the bottom of this cavity might 

 cause the rail to snap as instantly if the load of the train 

 above hammered down too suddenly as if it contained the 

 pipe. Such a rail can generally be detected only by the 

 etching method and the microscope. Fig. 6 shows a rail 

 with a great many sulphur flaws present, the dark areas 

 representing the flaws. 



