132 Prof. H. F. Weber on Electromagnetic and 



For 23° the platinum wire possesses the absolute resistance 



14-468 x 10- fi*®£±\ 



V sec. / 



and the relative resistance 



15-146 S. M. U. ; 

 and for 0° the platinum wire possesses the absolute resistance 



14-131 x 10™ (^H 

 \ sec. / 



and the relative resistance 



14-781 S.M.U. 



From the first result it follows that 



1 S. M. U. =0-9552 x 10 10 (E^^Y; 



\ sec. / 



from the latter, 



1 S.M.U. =0-9560 x 10 10 ("^^V— 



\ sec. / 



which are in perfect harmony with the results previously ob- 

 tained in sections I. and II. We obtain the coefficient of the 

 increase of the resistance, referred to 1° of temperature- 

 increase : — 



From the absolute measurements, <7= 0-001035.") 



And from the relative measurements, q = 0*001074.-' 



For the temperature t a , employed in the experiment in ques- 

 tion, the absolute value w a was calculated according to the 

 formula 



«?= 14-131 [1 + 0-001054 1] xl0 10 ( m ^ m, V 



From the results adduced it follows that absolute determi- 

 nations of resistance can be accomplished with such precision 

 that the variability of the resistance with varying temperature 

 can be ascertained from them very nearly as accurately as 

 from resistance-comparisons according to the bridge-method. 



In the course of the investigation a gradual alteration of the 

 resistance of the platinum by the continual passage of currents 

 through it was sought after with peculiar care. On the 16th 

 October, 1876, at the temperature of 23°"7 the resistance was 

 found equal to 15*154 S. M. U., or, reduced to 16°, equal to 

 15*032 S. M. U. 



After the wire had served, for twelve experiments, in which 

 a current of absolute intensity 4 (a round number) passed 

 through it during about an hour, it showed, on the 19th De- 



