AND LIQUIDS AND THEIR VARIATION WITH T 431 



The conductivities given in the preceding table depend on that of the disc of glass 

 between the upper and middle copper discs, which was determined in Part I. 



Previous to the apparatus with the glass disc being constructed, experiments had 

 been carried out with the apparatus in which rubber replaced the glass. As the 

 conductivity of this rubber was unknown, the results obtained were all expressed 

 in terms of the conductivity of water. By means of the value for water found in 

 Part IT., these relative values have been converted into absolute values, and are 

 given in the table which follows. 



The discs were not in this case surrounded by a vessel of known temperature, but 

 were exposed to the air, the temperature of which was observed. The lower disc was 

 placed in the top of a vessel through which cold water circulated, and the observa- 

 tions were taken in the manner previously described. 



The theory of the method is identical with that given on p. 422, except that the 

 constant A is zero. 



Constants of Apparatus. 



r = 2 centims. TTT~ = 12 '5 sq. centims. 



r t = 1-855 ,, irri = 10'8 



t t = '132. 



t R = '110, therefore f u /4 '027 centims. 

 M = '320 + '075 = -395 



h = -00030, therefore 2irrh E/ 4 = '00010 



. = '00148 



Sum . . = -0016 



