1 8 Schwartz & Kemp, Physical Properties of Rubber. 



These tests point to the fact that the previous history 

 of the specimen is of great importance in determining the 

 strain resulting from a given stress. 



Further experiments with a greater load on the 

 specimen showed that a small initial contraction followed 

 by a rapid expansion resulted on the application of heat. 

 On further increasing the load it was found that, under 

 loads sufficient to give an initial extension of the order 





Fig. 9. 



Spread Rubber Tapt, Rested for 3 Years. Tested under Tension of 

 50 grams. = 167 lbs. per sq. inch. 



of 100%, the application of heat was found to lead to 

 contraction only. There is evidently, therefore, some 

 critical load up to which the application of heat results in 

 expansion and beyond which contraction occurs. In the 

 discussion following the reading of this paper Professor 

 Gee pointed out that Schumlewitsch* had come to the 



* Schumlewitsch. " Ueber den Kautschuk," I'/crU/Jalirssch. dcr 

 Natiirforsch. dsell. Zitriclu 1866. 



