lO 



ROYAL SOCIETY OF CANADA 



The result of Dewars work is to show that the specific heat of ice 

 decreases rapidly with the temperature as follows: — 



Between —18° 



—78° 

 " —188° 



—78° 



—188° 



—258.5 



0.463 

 0.285 

 0.146 



The agreement with Eegnault's result between 0° and —78°, which is 

 0.474, is remarkable. 



Conductivity of Ice. 



The thermal conductivity of ice was first determined by Forbes in 

 1874, using a method proposed by Kelvin. A disc of ice, 12 inches in 

 diameter, was formed by placing a freezing mixture about a vessel of 

 water kept constantly at 0°C. With suitable thermometers in the ice 

 disc, the value of the conductivity, K, which he found was the fol- 

 lowing : — 



Along principal axis .. .. 0.134 

 Perpendicular to axi= .... 0.128 



these were expressed in C. G. minute units. 



Mitchell, in 1885, used Angstrom's method of periodically heating 

 and cooling the end of a bar of ice and determining the period of the 

 waves set up in the bar. He found in C. G. S. units the value .005 foi 

 the conductivity. F. Neumann used the periodic method with more 

 success. He found for K the value .00573 in C. G. S. units. 



Straneo, in 1897, using the guard-ring method, found values for 

 the conductivity of ice in two directions to be nearly the same, i.e.. 



Along principal axis 0050 and .00517 



Perpendicular to axis 00514 



TABLE VI. 

 Thermal Conductivity of Ice. 



