724 Transactions of the American Institute. 



by twelve inches or 228 square inches. These were the weakest 

 places. 



The following were the grate and water heating surfaces of the 

 boiler. 



Grate surface 79f§- square feet. 



Heating surface in furnace 180 



Heating surface in combustion-chamber and back- 

 connection 103 



Heating surface in tubes 2 > 181 



Heating surface in uptake 64 



">g 



u 

 Total heating surface 2,318 " 



On the 2d of September last this boiler was subjected to a hydro- 

 static pressure of sixty pounds per square inch, when twelve crow-feet 

 gave way. After being repaired, it was again subjected on the 8th 

 of November last, when erected at Sandy Hook, to a hydrostatic 

 pressure of fifty-nine pounds per square inch, which it bore without 

 fracture ; and on the 16th of November last it was subjected to a 

 steam-pressure of forty-five pounds per square inch, which it also sus- 

 tained without fracture. 



The fuel used in the experiment was wood, and the water-level in 

 the boiler was fifteen inches above the highest point of the tubes. 

 When the fire had been brought to a steady action the pressure of 

 the steam gradually increased at the following rate, commencing with 

 the pressure of twenty-nine and a half pounds per square inch. 



Steam pressure in 

 Time p. M. pounds per square 



, ' , inch above the at- 



Hours. Minutes. mosphere. 



12 21 29* 



12 23 33i 



12 25 37£ 



12 27 41 



12 29 44£ 



12 30 46^ 



12 31 48£ 



12 32 50 



12 33 52 



.12 34 53£ 



At the pressure of fifty pounds per square inch, some of the braces 

 in the boiler gave way with a loud report, and when the pressure of 

 fifty-three and one-half pounds was reached, the boiler exploded with 

 terrific violence. The steam drum and a portion of the shell attached 

 to it, forming a mass of about three tons weight, were hurled to a 

 great height in the air and fell to the earth at about 450 feet from the 



