768 Transactions of the American Institute. 



what less than the true value, and it may be more nearly correct to 

 take 275 feet as the height due to the noted range. The work done 

 in raising the steam drum to this height was 687,500 foot-pounds, and 

 the pressure which, acting through a space of 4.5 feet upon the base, 

 would correspond to this amount of work, is 37.5 pounds. 



This figure is in excess of the real pressure required, for the reason, 

 as already stated, that a part of the shell was attached to the steam 

 drum, assisting in its propulsion to an extent which is a matter of 

 mere conjecture, and which not improbably reduces the given pressure 

 several pounds. 



The actual height of ascent of this piece was variously estimated 

 by the spectators at from 200 to 400 feet, and, by one individual at 

 least, even considerably higher. As, in such cases, heights are 

 usually over-estimated, the lower figure is most likely to be nearest 

 the truth. 



It would be impossible to make the last two estimates so closely 

 approximate to accuracy as to entitle them to great confidence, and 

 the other calculations are merely estimates of improbable actual 

 effects. 



The writer is, however, inclined to conclude : 



1st. That it is very certain that the energy of this explosion, and 

 all of its tremendous effects, were principally due to the simple 

 expansion of a mass of steam suddenly liberated, at a moderate press- 

 ure, by the general disruption of a steam boiler of very uniform but 

 feeble strength. 



2d. That, in this case, the liberation of steam throughout the mass 

 of water contained in the boiler, and which took place by the evapora- 

 tion of one pound in every thirteen of the water, and which resulted 

 in setting free nearly 70,000 cubic feet of steam, would not seem to 

 have taken place promptly enough to greatly intensify the effects of 

 the explosion. 



3d. It would seem very doubtful whether Zerah Colburn's hypothe- 

 sis — which explains the violent rupture of steam boilers by the sup- 

 position that the steam, liberated from the mass of water in cases of 

 explosion, carries with it, and violently projects against those parts of 

 the shell immediately adjacent to the point of primary rupture, large 

 quantities of water, which, by their impact, extend the break and 

 increase the destructive effect — can have had an illustration in case 

 under consideration. 



We have no right to conclude that such an action as Colburn 

 described may not occur in many cases of explosion ; on the contrary, 



