592 



Professor Ernest G. Coker 



[Feb. 18, 



Compression tests may therefore be expected to show more 

 consistent results when the load is applied through an intermediate 

 layer of the same material, since it is apparent that the practice of 

 testing every kind of material in compression between hard steel 



cy 



to 



I 



MOO 



1.200, 



1.000 



aoo 



600 



,400 



200 



■4- 



Fig. 10. 



Q 



to 



face plates with quite arbitrary facing material, causes an error which 

 varies widely in amount with different bodies, and even with different 

 specimens of the same kind of substance. 



The application of optical methods of investigation to other 



