Manchester Memoirs, Vol. Iv. (191 1), No. 12. 15 



each case. The curve ' A ' in Fig. 7 is that obtained from 

 a virgin specimen, and shows an expansion throughout the 

 whole range of the experiment, the co-efficient of Hnear 

 expansion gradually increasing as the temperature was 

 raised. In the case of the curve 'B,' the specimen was 

 cut from the same sheet as 'A,' but was stretched to 

 double its original length, and held in this condition for 



^ 



<^ a 



Te»tpej-erfi/r-A /n °C 



Fig. 7. 



88% Rubber Vulcanised. 



A = Virgin specimen. 



B = Specimen stietclied ioo% for 5 minutes. 



five minutes. The tension was then removed, and the 

 specimen allowed to rest for a period of three or four 

 hours, in order to reduce the effects of sub-permanent set. 

 The test was then proceeded with and the curve ' B ' was 



