88 



Experiments on the Value of the Ohm. [June 15, 



being obtained from observations of the oscillations of the needle 

 about its position of rest, the chance of error is much smaller than in 

 the throws. 



Each set of experiments is the mean of four ; one for each of tlie 

 four positions in which the coils could be placed by inverting first one 

 and then the other without altering the distance between their 

 centres. 



Part I, which we regard as preliminary, contains the result of three 

 such sets, and from it we find 



1 ohm=-98598 earthquadrant . 



second 



The mean distance between the mean plane of the coils was 15 '01 9 

 centims. 



In Part II three series of experiments are described for different 

 distances between the mean planes of the coils. 



In Series A this distance was 15*019 centims. 

 „ B „ 18-252 



„ C „ 26-692 



Different batteries were used. 



The following table gives the values of R in earth quadrants/sec. 

 arranged in order of magnitude, with the battery used in each case, 

 the error of each result from the mean, and the percentage error. 



In the column headed battery, D stands for an ordinary cylinder 

 Daniell ; T for Thomson's sawdust tray Daniell. 



Table. 



Series. 



Battery. 



It. 



Error. 



Percentage 

 error. 



B 



5 T. 



158-106 



- -216 



- 135 



A 



4 D. 



158 '168 



- -154 



- -096 



A 



5 T. 



158 -231 



- -091 



- -057 



C 



6 T. 



158 -238 



- -084 



- -052 



B 



5 T. 



158 -303 



- -019 



- -012 



C 



5 T. 



158-332 



•010 



•006 



A 



4 D. 



158 -407 



•085 



•052 



A 



2 D. 



158-499 



•177 



•110 



C 



6 T. 



158 -611 



•289 



•181 



Mean value of R 158-322 earth 3™*™*. 



second 



Mean of errors "125. 

 Mean of percentage errors "078. 



