Polytechnic Association. 763 



pressure less than that which it had successfully withstood at the 

 hydrostatic test. 



" The last boiler had been tested to fifty-nine and one-half pounds. 

 This fact, too, although frequently urged by some engineers, was 

 generally disbelieved. It has now been directly proven." 



In a foot note I say : 



"A number of instances of this kind, though not always pro- 

 ducing an explosion, have been made known to the writer. 



" Two boilers at the Detroit water-works, in 1859, after resisting 

 the hydrostatic test of 200 pounds, with water at a temperature of 100* 

 Fahrenheit, broke several braces each at 110 and 115 pounds steam 

 pressure respectively, when first tried under steam. 



" The boiler of the United States steamer Algonquin w r as tested 

 with 150 pounds cold-water pressure, and broke a brace at 100 pounds 

 when tried with steam. 



" A similar case occurred in New York, a few years ago, and the 

 boiler exploded with fatal results. 



" These accidents are probably caused by changes of form of the 

 boiler, under varying temperature, which throw undue strain upon 

 some one part, which may have already been nearly fractured." 



In the same article I say : 



" More than thirty-five years ago, a committee of the Franklin Insti- 

 tute made a series of experiments of such extent and accuracy that the 

 republication of their reports, and their circulation among engineers, 

 would to-day be a public benefaction.* Their report, together with 

 the paper of F. A. Paget, on the " "Wear and Tear of Steam Boilers," f 

 and the little book of E. B. Martin ^ on explosions, should be in the 

 library of every engineer. 



" The experiments of the committee of the Franklin Institute were 

 made upon a small scale, and upon constructions quite different in 

 form from most steam boilers, and, although the information obtained 

 was invaluable, it still remained desirable to repeat their experiments, 

 and to make other investigations with boilers of full size, such as are 

 used in steamers, on our railroads, and in our manufactories." 



After describing the experiments I continued : 



" Having briefly described these experiments, it may be well to notice 

 what bearings their results have upon existing beliefs, and how far 

 they extend our knowledge of the causes and conditions of explosions. 



* Tide Journal Franklin Institute, 183C, Vol. XVII. 

 t Ibid., 1865, Vol. I. 



$ Records of Steam Boiler Explosions ; E. B. Martin. London : E. & F. N. Spon, 1871. 



t 



