52 I >r. ( '. < 'hive. / i on 



In the case of K 3 -K 4 , ami <>f lv{-t-K 4 ), the differences of 



resistance at the ice point are only about 0*4 of a box unit ; but the 

 ratios are based on a considerable number of harmonious observations, 

 and the smallness in their fluctuations from one year to another appears 

 incompatible with any serious error. 



The only case in Table XX in which there is unmistakable change 

 in the values of Ri/Ro and R/Ro with the time is KI - '(K :< + K 4 ). 

 The change in this case is conspicuous, and supports, of course, our 

 previous conclusion that KI has undergone some alteration. 



49. If we omit combinations containing KI or Kj, we notice a 

 curious resemblance between the values of the ratios in the different 

 cases, and this same similarity appears in other combinations of the five 

 thermometers K 3 , KI, KS, K;, and Kj (when multiplied by 0'4) which I 

 have tried. We always get something pretty close to : 



Ice point difference : steam point difference : sulphur point differ- 

 ence :: 1 : 1-6 : 3'6. 



The phenomena presented by these five thermometers are thus pretty 

 much the same as if their spirals consisted in the main of given equal 

 lengths of identical platinum, with, in addition, variable lengths of a 

 material whose temperature coefficient is higher than that of platinum. 

 In this imaginary material the resistances at the ice, steam, and sulphur 

 points would be approximately as 1 : 1 '6 : 3*6. Another way of stating 

 the fact would be that the changes in the resistance of the imaginary 

 material due to temperature are about 1'56 times as great as in 

 platinum. 



In addition we can closely reproduce the figures resulting from the 

 comparison of K-2 with the other thermometers by supposing that Kj 

 has a smaller quantity of this imaginary foreign material than the 

 others, but a larger quantity of pure platinum. 



The figures to which my calculations lead for the resistances at 0, 

 due to the foreign material and the pure platinum, are as follows, in 

 terms of the mean box unit : 



Resistance, Resistance, 



Thermometer. foreign material. platinum wire. 



K 2 Z Z + 5'150 



K 7 2 + 0-637 x 



K 4 -s + 1-391 x 



K 3 2+1-783 x 



K 5 2 + 2-223 * 



Taking, for instance, the cases Ko - K^ and K 2 - Ky in 1899, we have, 

 in mean box units 





