POLYTECHMC ASSOCIATION. 721 



Steam-pressure in 

 Time p. m. pounds per square 



, 1 i • inch above the 



Hours. Minutes. atmosphere. 



3 38 58 



3 39 65 



3 40 72 



3 41 78 



3 * 42 86 



3 43 94 



3 44 100. 



3 45 110 



3 46 , 117 



3 47 : .. 126 



3 48 135 



3 49 147 



3 50 160 



3 51 165 



When the pressure reached 165 pounds to the square inch, the box 

 exploded with a loud report, completely demolishing the brick-work 

 by which it was inclosed. The two sides were hurled in exactly oppo- 

 site directions, and to about equal distances, at right angles to their 

 surfaces. The fracture had occurred in one plate only, and was along 

 the whole riveted seam joining it to the frame. For a large part of 

 the length of the seam this plate was torn out between the rivets, and 

 for the remaining part the rivets were sheared. The other plate was 

 not fractured, nor were the bars of the frame broken ; the plate and 

 the frame remained riveted together, but not uninjured, all the bars 

 of the latter being bent considerably inward, forming an irregular 

 curve of from four to six inches versed-sine. Both plates were bulged 

 out irregularly, so as to be about nine inches dishing, and the bulging 

 took place near the bars. Not one of the bolts was broken, and 

 neither the threads upon their ends, nor the threads in the plates, 

 were stripped or injured, but the slight riveting over the ends of the 

 bolts was broken off in all of them. 



The fact that the plates did not rupture at the center, under their 

 great amount of bulging (and only one of them tearing off at the line- 

 of rivets along its edge), shows the excellence of the metal which 

 endured this great, almost instantaneous and permanent stretching 

 without fracture; and to this same extensive stretching .must be 

 attributed the escape of the screw threads on the ends of the bolts, 

 and in the plates, from injury. The plate, by stretching, simply 

 enlarged the diameter of the hole in which the- threads were cut, 

 until the bolt, thus left free, slipped through without injury to its 

 threads, only breaking off the slight riveting over its ends. Had 

 [Inst.] 46 



