8 ROYAL SOCIETY OF CANADA 



The readings show that with this rate of loading the stress and 

 thermal change reach a niaximnm at practically the same time, and 

 then, owing to losses by conduction and radiation, the bar gradually 

 warms up to the temperature of its surroundings. The deflections 

 given in Table T are plotted in Figure 1 to a time basis, and it will be 



$ rvfrti/res 



T'/fiE 



noticed that the ascending part of the curve does not show a linear 

 relation to the stress, but if allowance is made for the disturbing causes, 

 the relation can easily be shown to be a linear one. 



Since the effect of lag of the galvanometer may be regaifled as 

 eliminated by proper adjustment of the rate of loading, we may obtain 

 a correction factor for the conduction and radiation in the following 

 way. 



Let é'o be the diminution of temperature per second due to the 

 application of a stress increasing uniformly with the time, and let B be 

 the actual difference of temperature at any time from the commence- 

 ment of the application of stress, then since there is a loss of heat, 

 ^ < ^„ f and this loss depends on the difierence of temperature 

 between the specimen and the surrounding bodies. 



This I0S.S can bo very approximately determined by observations of 

 the subsequent readings when the stress remains stationary, and it was 



