﻿2 POPPLEWELL, Uniform Stress and Permanent Strain. 



In the present paper a number of further tests on 

 wrought iron and steel compression specimens are 

 described. 



Eight specimens were tested, four being of mild steel, 

 and four of wrought iron of average quality. The test 

 specimens, which were of cylindrical form having a height 







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 i 



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Fig. i. 



twice the diameter, were placed between the compression 

 dies of a testing machine and successive definite loads 

 applied. The form of the bar is shewn in Fig. i. 



Each load was allowed to remain upon the bar for 

 about twenty minutes : after this it was taken out of 

 the machine and the permanent set determined. In 

 every case the length of the bar between its flat ends was 



