Polytechnic Association. G3£ 



boiler; another that the safety-valve was not in order; one that it 

 was bad iron; another that it was bad workmanship; another that it 

 was badly designed ; another that it was badly stayed ; one that there 

 was a generation of electricity ; another that the boiler was oxidized, 

 and thereby so weakened as to be incapable of standing the pressure 

 applied to it. . 



Mr. ~\Y. proceeded, to make a drawing of the boiler, and to explain 

 how it was exploded. It separated at the bottom, and two seams 

 being weak, one course of the shell was rolled over like paper, sepa- 

 rating at the line of rivets on both sides, and one end of the boiler 

 was projected into the eyes of the ship, and the other end was moved 

 two feet and brought up against some timbers. All this operation 

 must have occurred in an incredibly short space of time ; because, if 

 the rupture had been gradual, the reaction, when the sheet was 

 half removed, would have thrown the boiler over the side of the ship; 

 but, instead of that, both ends were projected in a line parallel with 

 the keel. 



The first theory I shall refer to is that of over-pressure. A cylin- 

 drical boiler, subjected to elastic pressure, will be ruptured longitu- 

 dinally with half the pressure that will cause it to rupture trans- 

 versely. Another rule is, that any piece of metal subjected to tensile 

 strain will be extended permanently by about half the force that will 

 break it. If, then, we cannot find in a boiler any part of ecpial 

 strength with the part that gave way, permanently extended, we may 

 be sure that the boiler did not burst by over-pressure. There is no 

 part of the boiler of the Westfield that exhibits the slightest evidence 

 of permanent extension, otherwise than at the point of rupture ; and 

 I conclude that over-pressure of the steam was not the cause of the 

 rupture. • 



If a boiler were burst by over-pressure, the permanent extension of 

 parts which did not give way would be so great that it would be 

 impossible to repair it. When the boiler of the steamer St. John 

 exploded, some years ago, I know that the boiler was repaired, and 

 that when steam was put in there was no leak anywhere ; so that 

 there was no strain on that boiler sufficient to cause permanent 

 extension of the iron.- And I venture to say that no engineer ever 

 saw in an exploded boiler any indication of over-pressure. The indi- 

 cations would be that the steam-gauge would suddenly advance, the 

 engine would move more rapidly, the condenser would become hot. 

 There is no reliable evidence that any such indications have ever been 

 observed. 



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