202 Mr. H. H. Poole on the Temperature Variation 



small circles, two different diameters being used for alternate 

 isotherms. The parallelism of the lines indicates that B is 

 independent of the temperature within the limits of error. 

 The value found for it is 0'787. The value of A for different 

 isotherms was found to agree fairly well with the formula 

 A = 43*34 + 15*47 logT, where T is the absolute temperature; 

 so that the complete formula for C is 



log C = 43*34 + 15-47 log T + log X + 0787X. 



This shows that for a given value of X the current is propor- 

 tional to the 15*47th power of the absolute temperature over 



Fig. 3. 



the range covered. In order to show how this formula agrees 

 with the observations, it has been used to calculate the tempe- 

 ratures of the various isotherms. The results have been given 

 in the second column of the previous table, and it will be 

 seen that the agreement with the observed temperature is in 

 general fairly satisfactory, and in some cases remarkably so. 

 At 13°*5 0. and 16° C. the currents were too small to measure, 

 except with very large values of X when deflexions of a few 

 scale-divisions were obtained. The single reading obtained 

 at 13 0, 5 C. accorded perfectly with the formula given, but 



