Temperature Coefficient of Young's Modulus. 379 



curve 1, the magnitude of the effect obtained by Walker under 

 the same conditions. 



Table I. 



Temperature. 



Young's ModulusXlO" 



-n 



300 



19-35 





41-8 



18-65 





56-0 



18-64 





72-5 



18-1 





76-0 



17-69 





83-0 



17-89 





1100 



17-70 





124-0 



17-18 





139-0 



16-79 





260 



18-94 





285 



19-15 





340 



18-92 





470 



18-71 





610 



18-29 





950 



17-69 





Table II. 





Temperature. 



Young's Modulus X 10" 



i 

 -11. 



o 

 35-5 



21-50 





46-0 



21-30 





51-0 



20-95 





590 



20-30 





660 



20-80 





76-5 



20-75 





82-0 



20-44 





1020 



20-06 





112-0 



19-81 





121-0 



19-45 





54-0 



21-28 





72-0 



20-57 





Minimum load = 12 kilos/sq. mm. 

 Maximum load=25'6 kilo9/sq. mm. 



Minimum load 

 Maximum load: 



12 kilos/sq. mm. 

 21 kilos/sq. mm. 



Results. 



The chief conclusions deduced from the detailed exami- 

 nation of Young's modulus for iron between 27° and 140° 

 are as follows. 



Both in annealed and unannealed portions of wire the 

 isothermal modulus decreases continuously as the temperature 

 rises. There is no indication of a maximum within the ran^e 

 of temperature or load employed. The results in the case of 

 the annealed specimen can be represented by the parabola 



5» - 1 _ -000934(0- 30) - -000,000733(0 - 30) 2 , 



where E 30 = 18'95 X 10 u dynes/cm.' 2 ; 



and in the case of the unannealed specimen (slightly hardened 

 by stretching) by the parabola 



5l = 1- -000922(0- 30) - -000001 19(0 - 30) 2 , 



-^30 



where E 30 = 21*60 x 10 11 dynes/cm. 2 . 



All load elongation graphs are linear within the limits of ex- 

 perimental error, the loads employed varying between a mini- 

 mum of 12 kilos/sq. mm. and a maximum of 25*G kilos/sq. mm. 



