1881.] Determination of the Ohm in Absolute Measure. 139 



obtained by calculation on the assumption that the coefficient of self- 

 induction of the coil is 4*51 x 10 7 centims. This absolute resistance 

 refers to the German silver coil, and a small length of the bridge wire 

 at a given temperature. As both the temperature and this length 

 of bridge wire varied in different experiments, the different results 

 cannot be directly compared, but we can easily apply a correction 

 which shall reduce the numbers to the absolute resistance of the 

 German silver coil at a fixed temperature. The temperature chosen 

 was ll°-5 C, which was approximately the lowest temperature observed 

 in the course of the experiments. The fifth column contains the 

 corrected values, which now can be compared together, and give the 

 absolute resistance of the standard coil as observed on different 

 occasions, and with different speeds. In the last column the mean 

 value for the different speeds is given. In taking these, as well as the 

 final mean, it must be observed that the set of observations made on 

 December 10 with speed 60 teeth contained only two spins, or half the 

 usual number. 



Date. 



Speed. 

 No. of teeth 

 on stationary 

 card. 



Deflection. 



R x 10- 9 . 



E x lO- 9 

 corrected. 



Mean. 



Dec. 1 ... 

 10.. . 



120 



110 -42 

 110-22 



4 -5486 

 4-5568 



4 -5419 

 4 -5309 



4 -5364 



Dec. 2... 

 6... 

 10... 



60 



218-61 

 218-30 

 218-72 



4-5580 

 4 -5620 

 4-5531 



4 -5487 

 4 -5471 

 4 -5422 



4 -5467 



Dec. 2 ... 

 6... 

 10... 



32 



397 -75 

 397 -39 

 397 -26 



4-5639 

 4 -5672 

 4 -5687 



4-5417 

 4-5415 

 4 -5448 



4 -5427 



Pec. 2 .. 

 6 .. 



24 



513-73 

 513 58 



4 -5719 

 4 -5734 



4-5446 

 4 -5438 



4-5442 



The mean of all the observations is — 



4*5427 ear ^ n cp^drant 



second 



The value of the self-induction which was adopted in these calcula- 

 tions is slightly smaller than the values calculated by Lord Rayleigh 

 and Mr. Niven. A comparison of the results obtained with different 

 speeds shows that the value must be very nearly correct, for there is 

 no decided difference between the results. Nevertheless, it seemed of 

 interest to calculate the value of the self-induction which best agreed 

 with the experiments, and to see whether that value gave an appreciably 

 different result for R. 



