HOLMAN. — THERMO-ELECTRIC FORMULA. 



205 



The deviations in microvolts and percentages from this equation 

 are given in columns five and six, Table III. 



Tlie exponential equation fitting these data most closely, and coin- 

 ciding with them as nearly the same points as the others, viz., at 

 about 584° and 1250°, is 



%e = 0.57 674 t^""'' ~ 1310, or 

 e = 0.57G74Ti"^y8= 1310. 

 Range 0° to 1445° C. 



The deviations in microvolts and percentages are in columns seven 

 and eight, Table III. 



The logarithmic equation applied to the Holborn and Wien data 

 on A yields 



2,',e=: 2.1682 ^i-^i^!, or 



log %e = 1.2156 log t + 0.36 610. 



The deviations are given in the last two columns of Table III. 



Holborn and Wien not only compared the ten per cent rhodo-plati- 

 num couple A directly with the air thermometer, but compared 

 with A seven other couples in which one element was platinum, 

 and the other a rhodo-platinum alloy, the percentage of rhodinum 

 being stated respectively as, for Ci and C2, 10 per cent (these two I 

 have combined under C), D, 9 per cent, E, 11 per cent, F, 20 per cent, 

 G, 30 per cent, H, 40 per cent. For the present purpose I have com- 

 bined these data, which were differences of emf. between C and A, D 



TABLE IV. 



