SIR WILLIAM SIEMENS, F,R.S. 271 



that similar results would be obtained with iron, though it might 

 not be so easy always to obtain the same degree of regularity with 

 that material. He thought that the limit of elasticity of a mate- 

 rial was of much greater practical importance to engineers than 

 its ultimate breaking strain ; because a structure was safe if no 

 part of it was loaded past the point of limit of elasticity, but must 

 ultimately fail if that limit was exceeded. 



In the discussion of the Paper 



" ON THE TESTING OF RAILS ; WITH A DESCRIP- 

 TION OF A MACHINE FOR THE PURPOSE," 



By JAMES PRICE, M. Inst. C.E. 



MR. C. "W. SIEMENS* said that having lately made some experi- 

 ments with steel rails and iron rails, he could bear out the author's 

 remarks, confirmed already by Mr. Bramwell, as to the great sus- 

 ceptibility of steel to break under the influence of a shock. The 

 paper which Mr. Bramwell read before the British Association f 

 pointed out the reasons why it was so. In the case of an iron rail 

 there were innumerable fibres capable of yielding individually to 

 take a greater strain when necessary. Now in the case of steel 

 which was homogeneous, no such independent fibrous action could 

 take place, and if one part of the line of strength was broken an 

 indefinite amount of tearing strain was thrown upon the adjoining 

 part. In trying steel rails under a blow, he found that where an 

 entire rail would stand the impact of a ton weight falling 20 feet, 

 in the case of a rail being supported rigidly between 3 feet bear- 

 ing, a blow from a fall of only 4 feet of the same weight would 

 break it at the place where the hole was drilled through the web 

 of the rail. It followed from this experiment that in drilling or 



i 



* Excerpt Minutes of Proceedings of the Institution of Civil Engineers, Vol. 

 XXXII. Session 1870-71, pp. 206-208. 



t Vide Report of British Association, 1859, p. 422. 



