446 



DR. CHARLES H. LEES ON THE EFFECT OF TEMPERATURE ON Till! 



s 1 

 In the apparatus used / = 4'2 centims., .s = '6 centim. Therefore j = - 



p = '131. Therefore ?g = "0490. 



c = -395. 



= -1477. 





= '2954. 



Therefore 



a = -975. 



H 28 1 



= -3646. 



HIT 



+ 4 X 



0=1,3,5 



Since terms of the form 



cos ax 



P=2.4, 



r cos 



have disappeared from the final equation for v l v 2 , the same value of the temperature 

 difference would be obtained from assuming that the brass tube was not at a uniform 

 temperature V, but at a temperature 



V + cos ax\ AJo (ar) + S A^l^ (ar) cos $6 , 



L 0=2,4,6 J 



where a, A. f are arbitrary constants. 



If, further, the temperature of the brass tube is a function of the time, symmetrical 

 about the axis of the tube, we add to the preceding solution terms of the form 



cos 



. e lt , 



without altering the value of the observed temperature difference. This furnishes 

 the justification for the use of the apparatus while its temperature is increasing or 

 decreasing owing to its relation to its surroundings.* 



The above theory has been worked out on the assumption that the heating wires 

 and temperature spirals were directly embedded in the material of conductivity I: 

 In the apparatus used the heating wires were enclosed in narrow glass tubes round 



* It is however still possible that if the rate of change of temperature is great, the change of 

 conductivity or specific heat of the substance may be sufficiently large to affect the result. In no case 

 has any effect of the rate of healing on the result been detected. 



