364 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



Calculation of the Temperature, 



In estimating changes of temperature by means of changes of resist- 

 ance, using Callendar's method,* it is necessary to know the average 

 value of the temperature coefficient for the copj^er between 0° and 100°, 



or the ratio 



i?„ 



Where 



R.^ =: resistance at 1 00° C, 

 E^ = resistance at 0° C. 



Let 7?=. the observed resistance. 



Let Ca = temperature on copper resistance scale. 



Let t — temperature on air thermometer scale. 



The ratio — I was taken 



-^0 



1.422. 



Temperatures are calculated according to the formula 



100 



Cu - ^-^' X 



Rn 



— 1 



(1) 



* H. L. Callendar, Phil. Trans., 1887. 



