248 



Prof. Cams-Wilson. 



FIG. 1. 



bar is 183/100 of any one in the plain, the resistances of all the plan 

 will be in the same ratio.* 



In this specimen (No. 831), the ratio of the true breaking stresses 

 is actually 120 : 100. But there are four causes tending to reduce 

 the strength of the grooved specimen, as has been shown above, viz. : 

 The non-uniformity of stress, the possibility of a pull not perfectly 

 longitudinal, the danger of observing too high a load on the plain 

 specimen, and, lastly, the crystalline nature of the steel at fracture in 

 the grooved specimen. 



* This assumes that the shearing stress is uniform orer both of these oblique 

 planes ; the probability of this supposition is discussed in a paper on " The . 

 bution of Flow in a Strained Elastic Solid," published in the ' Philosophical 

 Magazine/ for June, 1890. 



