Platinum TJiermomctry at Kew Observatory. 



51 



either thermometer. Consequently, if the platinum wire in the several 

 thermometers were identical, the differences between the resistances of 

 any two of them at the steam point and at the sulphur point or the 

 differences between any one and the mean of any two others should 

 bear to the difference of the resistances in ice constant ratios. And 

 according to Table XIX the values of these two constant ratios should 

 be approximately 1*387 : 1 and 2*631 : 1. 



Table XX shows what the ratios actually are in the cases examined. 

 In treating KG I utilised only those observations in which the differ- 

 ence between the leads could be allowed for. The meaning of the 

 results will be rendered clear by an example. The mean of the differ- 

 ences between corresponding observed values of RI in K 3 and K 4 

 during 1896 was 0'665, while the mean of the differences between the 

 observed values of RO was O405 : the ratio of these two quantities is 

 1 '64, and it is given under the heading RI/RQ. This is here used as an 

 abbreviation for 



(R! in K 3 less RI in K 4 ) -7- (Ro in K 3 less R in K 4 ). 

 Table XX. 



In only one case, K2 - K;, are the ratios even approximately equal to 

 the mean values given by Table XIX, viz., 1'39 : 1 and 2 '63 : 1. Even 

 in that case the differences are too big to ascribe to experimental error, 

 because the R of K2 exceeds that of K; by fully 4 '5 box units. 



E 2 



