[BOYLE] ELECTRIC CURRENT ON THE MODULUS OF ELASTICITY 163 



responding to a stress of 24,420 lbs. per sq. inch, or 1,718 kgm. per 

 sq, cm., and a strain of .001245, This gives a modulus of elasticity 

 of 22.37 X 10^ inch-lb. units, or 1.575 x 10® cm. — kgm. units. 



The specimen tested was 265.3 cm. long, and .0221" (=.0562 cm.) 

 diameter. It can be seen that below the elastic limit this material 



/ z a 



CMS. eXTCNSION f 



4 s 6 



.J77 , PER C£f^T STRETCH. 



Fig. 2. 



is very elastic and strong. Of course the same material with larger 

 cross-section would not be as strong in proportion, as we know that 

 pulling out and drawing through dies has a hardening and strengthen- 

 ing effect, and produces a hard and tough skin which is much stronger 



