﻿4 POPPLEWELL, Uniform Stress and Permanent Strain. 



cause the author, in the case of most of the bars, adopted 

 means for taking both end measurements and measure- 

 ments between lines scribed upon the surface of that 

 portion of the bar which was likely to remain sensibly 

 parallel during the time of the test. The precise way of 

 doing this was as follows : a fine centre punch dot a 

 Figs, i and 2, was made upon the surface of the bar about 



V 



s. 



i 

 I 

 I 



Fig. 2. 



one centimetre from one of its ends. A pair of dividers 

 were set to a radius of three centimetres, and a circular 

 arc b, c Figs. I and 2, was struck with this radius with 

 the centre-dot as centre, the mark being made upon that 

 portion of the bar towards its other end. This gave a 

 fixed distance of three centimetres marked upon the 

 surface of the bar. After a load had been applied to the 



