Cresson.] -jUO [^^july 17^ 



a pressure of over 570 lbs. per square inch in addition to tliat already- 

 existing in the boiler. 



The sudden opening of any outlet of pressure, such as the safety-valve, 

 throttle, vrhistle, blower or steam-cock to the donkey-pump, would pro- 

 duce a foaming or disturbance of the water-level in the water-space 

 surrounding the fire-box, causing the water to flow over the crown-sheet 

 in an amount quite sufficient to account for the disaster under the con- 

 ditions indicated. 



To illustrate the rapidity of the explosive force, let us suppose the 

 upper surface of the crown-sheet of the fire-box to have been covered 

 with gvinpowder to a depth equal to that of the water, which we have 

 shown could have been evaporated by it. If this powder were ignited in 

 the ordinary way, it would require from half a second to two seconds for 

 its complete combustion, according to the quality of the powder, whereas 

 an equal quantity of water thrown upon the crown-sheet could be con- 

 verted into steam in less than one second, the resulting volume of vapor 

 being nearly equal in both cases. 



Careful examination of the quality of the iron, and of the plan of con- 

 struction of the boiler, have convinced me that the boiler was amply 

 strong for the purposes designed, I am of the opinion that the disaster 

 occurred directly and solely from a neglect to keep the water within the 

 boiler at its proper level. 



The tests and experiments made, upon which the foregoing opinion 

 was founded, are as follows : 



A. — Tests of Strength op Iron. 



Test pieces cut from the worst looking part of the side-sheet of the fire- 

 box gave the following results : 



a. — With the length of the sheet. Dimensions of breaking section : 



Thickness 0.302 inch. 



Width 0.402 " 



Original length of piece 2.800 " 



After fracture 3.943 " 



Length of section extended 1.000 " 



Extension 0.143 " 



Breaking wt . per sq. in. 54,300 lbs. 



h. — Cut across the sheet. Dimensions of breaking section : 



Thickness 0.308 inch. 



Width 0.409 " 



Original length of piece. , 2.790 *' 



After fracture 2.890 " 



Extension 0,100 " 



Breaking wt. per sq. in 51,200 lbs. 



Length of section extended 1.000 inch. 



