62 MODERN SCIENCE READER 



pipe is removed, about twenty per cent, should be cut from 

 the top end of each ingot. Let us suppose, for sake of 

 illustration, that only ten per cent, is cut from the top of 

 each ingot, which is often the case; a "pipe" rail then 

 goes out to the stock pile with the good ones. 



But now suppose we have before us a fractured rail 

 broken by the impact of a heavy train going at a high rate 

 of speed? Suppose we polish it and examine it in just 

 the same way that we did our good rail? What shall we 

 find? 



We may find a partially welded pipe, which, it goes with- 

 out saying, is a source of weakness. This cavity, which 

 originated in our ingot when rolled, will look like the dia- 



C a 



FIG. 4. DIAGRAM OF THE PIPE IN A ' ' BLOOM, ' ' A PARTIALLY BOLLED 

 STEEL INGOT 



gram in Fig. 4. It can be readily seen that the long bloom, 

 as it is called, should be cut at C, and the butt sent to be 

 remelted; but if cut at A, the end of one rail, just where 

 great soundness is desired (near the joint), will be weak. 



Such a pipe will be revealed almost instantly by etching 

 a cross section of the rail and examining it under the 

 microscope; in fact in some cases the microscope is wholly 

 superfluous, for the defect and the reason for the disaster 

 will be visible to the naked eye. See Fig. 5. 



Let us go back to our ingot once more : at the foot of the 

 pipe the part which solidifies last, since top and sides cool 

 first will be found most of the impurities in the steel, the 

 most deleterious of which are phosphorus and sulphur. 

 Now a few tenths of a per cent, too much phosphorus or 

 sulphur in a steel rail will make it ''bad." These seem- 

 ingly infinitestimal amounts of sulphur make a rail snap 

 suddenly if worked hot; and worse yet, phosphorus will 



