132 Mr. J. Taylor oji tlie Accidents 



place, and almost immediately after an explosion, which made 

 him jump from a door-way considerably above the level of 

 the ground below, as the engine stands on the side of a steep 

 hill : — this door was used to discharge the cinders from the 

 ashpits. He alighted on the heap, and escaped out of the 

 way just before the hot water gushed out. Two other men 

 who were in the boilei'-house were not so fortunate, and they 

 were killed instantly by the boiling water ; no mark of any 

 other injury being to be found on their bodies. 



In this case, had the rush of flame from the fireplace any 

 thing to do with the subsequent explosion ? 



And admitting that the steam was so far within the pressure 

 that could by mere expansive force regularly exerted injure 

 such a boiler, — might not the rupture be occasioned by the aid 

 that a vacuum suddenly created might produce ? 



Does not the bursting of the one boiler after another as at 

 Polgooth, seem to indicate that exterior causes operated ? 



Is it possible to conceive, — supposing the pressure equal in 

 two boilers as was the case at Polgooth, both being connected 

 to the same steam-pipe, — that the relative strength of the two 

 should be so exacdy the same as that what would by mere 

 expansive force burst the one should have the same effect 

 upon the other? 



Have not all calculation and reasoning with respect to the 

 strength of boilers hitherto had regard merely to such expan- 

 sive force uniformly exerted ; and if we suspect or admit the 

 action of concussion, or the effects that any thing like a blow 

 would exert, ought we not to make a very different estimate 

 in their construction ? 



My intention was rather to state the facts than to attempt 

 an explanation of what is certainly at present very obscure ; 

 but that I may do all in my power to direct attention to the 

 subject, I will venture on a supposition. At the Pen-y-fron 

 engine we see that the fire-door is thrown open, and then the 

 current of air up the flue is stopped by closing the damper ; 

 the interior is filled with atmospheric air mixed to a certain 

 extent with coal gas ; the latter is increased by the distilla- 

 tory action of the fire until the proportion is attained which 

 is explosive ; it takes fire, producing the rush of flame which 

 would be followed by a sudden vacuum in the tube; while the 

 other side, pressed by the steam, gives way to this sudden im- 

 pulse, and is destroyed by a force very much smaller than 

 would be required if uniformly exerted. 



By some it has been suggested that hydrogen may have 

 been generated by the decomposition of water from leaks in 

 the boiler. 



That 



