42 



Mil. .1. MI-IK "N THK KKCOYKKY >F IK'.N FIJMM )VKi;Ml;.\l.\ 



|-|, ; >, BeneB of Compression Instrument Readings. (Test on a Virgin 

 illustrated I iy Curve 1. Diagram XII M 



The difference column given above shows that the material has behaved elastically 

 until a load of 20 tons per square inch was attained. Beyond that load there is 

 shown a gradual but tolerably rapid departure from HOOKE'S law ; there seems to be, 

 however, no very definite yield-point. In a tension test of this material creeping was 

 first noticed at 23 tons per square inch, and at 24^ tons a very large yielding occurred. 

 YOUNG'S modulus, as calculated from the compression readings given above, was found 

 to agree with that obtained from tension experiments to two significant figures ; in 

 both cases the third figure was rather doubtful. Thus, the modulus as got from a 

 first loading in tension to 20 tons per square inch, was 13,100 tons per square inch, 

 while from a second loading to 10 tons per square inch it was found to be 13,300 tons 

 per square inch. The modulus, as calculated from the contraction shown to have 

 occurred in the table above, between 4 and 18 tons per square inch, is 13,600 tons 

 per square inch. 



The second series of compression instrument readings was obtained from a specimen 



