STRENGTH OF STEEL. 



375 



not necessarily vary to any great extent with the other 

 properties, both chemical and mechanical, is shown by the 

 following figures, quoted by Johnson : 



MODULUS OF ELASTICITY OF STEELS HAVING DIFFERENT 

 PERCENTAGES OF CARBON. (MARSHALL.) 



Other tests by Mr. Marshall give the average elastic 

 modulus of nine bars of the same material as 13,710 tons 

 per square inch in tension, and the average result of nine 

 bars of the same material in compression as 13,150 tons 

 per square inch ; corresponding results from eight bars 

 of spring steel are respectively 13,170 and 13,070 tons 

 per square inch. The modulus is thus seen to be higher 

 in tension than in compression. 



RICKETTS' TESTS OF THE ELASTIC MODULUS OF STEEL. 



From experiments by Marshall, Trans. Am. Soc. C.E., vol. xvii. 



