Polytechnic Association. 637 



the temperature of incandescence; and even then the gas would be 

 so much expanded by the heat that the force of the explosion could 

 not be great. 



I next come to the driving in of the drift pin, and I assert that it 

 is impossible to break a sheet with the drift pin, from one rivet hole to 

 another. It is easy to account for their being found broken after the 

 boiler is exploded. Frequent heating and cooling of the iron may 

 cause it to bend back and forth and finally to break at the rivet 

 holes. 



As to the injudicious use of the caulking tool, the weakening due 

 to punching out the rivet holes is equal to .57 of the entire strength 

 of the iron, so that unless the caulking tool goes half way through 

 the sheet that could not cause the fracture. 



Pulsations would cause the sheet to bend at the seam, and would 

 be injurious. A boiler, when the pressure is removed, may settle 

 into an oval form from its weight, and, upon putting on steam, the 

 pressure restores its circular form. These changes would cause the 

 iron to bend at the seams and weaken it. 



Oil has no effect in a boiler, that I know of, except to prevent or to 

 cause foaming, and to prevent the oxidization of the sheets. 



The safety valve indicated a pressure of twenty-seven pounds, for 

 the engineer says it was "just simmering." I never saw any reason 

 to apprehend that a safety valve failed to open at the proper pressure- 

 Mr. Richardson invented a safety valve which would not only open 

 with certainty at a certain pressure, but which remained open until 

 the pressure was reduced several pounds. But although that safety 

 valve is now almost universally used upon locomotives, there are about 

 as many explosions as before. 



I examined the quality of the iron of the "VVestfield boiler very 

 carefully. It has been found, of many tests applied during the war, 

 that the best and most reliable test for iron is the sharpness of its 

 fibers when the iron is broken. If it will scratch the finger, the iron 

 is strong. I found, on applying that test, that the fiber of the "West- 

 field boiler iron was remarkably sharp. It seemed like a handful of 

 needles. The iron was, therefore, really of a very good quality. 

 There seemed to be an attempt by the maker of the boiler to make 

 it very superior. 



The manner in which this boiler was stayed has been complained 

 of. As it was constructed, the boiler was six times as strong to resist 

 longitudinal fracture as to resist transverse fracture. Then there were 

 tubes running longitudinally, and for the shell to break transversely 



