the Investigation of Young's Modulus for Wh 



551 



similar figures for sof 



t iron are : — 



Percentage 

 decrease 



Temp. 13°. 



1000° C, 



[of modulus. 



No. of bauds: 178*3 



1765 



-1-00 



176-4 



178-3 



+ 1-07 



177-1 



175-3 



-1-01 



173-1 



179-6 



+ 3-75 



176*3 



178-3 



+ 1*14 



1764 



179-2 



+ 1-58 



176-5 



178-5 



+ ri3 



175-6 



178-5 



-fl-65 



175-8 







The specimen of steel 



referred to above gave 



: — 



No. of bands: 149'1 



148-0 



-0-74 



144-4 



148-3 



+ 2-7 



143-6 



148-3 



+ 3-3 



143-5 



148-2 



+ 3-3 



143-4 







Similarly, for hard brass :— 





No of bands: 315*0 



310-5 



-1-43 



297-0 



303-7 



+ 2-25 



293-7 



302-7 



+ 3-06 



292-8 







Hence in all cases the final value of the modulus was lower 

 for the higher temperature than for the lower : viz. 3' 6 per cent, 

 for copper, 1*6 per cent, for iron, 3*2 per cent, for steel, and 

 3 per cent, for hard brass. It is interesting to note that, with 

 the exception of the brass, these figures are in the same order 

 as those given above for the increase of elasticity from 

 beginning to end of observations on each specimen. 



In almost all cases after any change of temperature, or after 

 a rest (of any time more than half an hour, say), the first 

 observation of the series showed an amount of elongation 

 different from those given by succeeding observations of the 

 same series, the first elongation generally being greater than 

 those succeeding. 



The following numbers are taken from results of observations 

 on soft iron : — 



First Succeeding Percentage 



Elongation. Elongations. Change. 



180-0 176-5 -1-94 



180-0 176-4 -2-0 



176-7 176-3 -0-22 



179-9 179-5 -0-22 



180-0 178-8 -0-66 



1795 177-7 -1-0 



2 P2 



