Shepard — New Solution for the Copper Voltameter. 55 



Series VI. 



Current Density '07 r- 



cm 2 



No. Equivalent x 10 7 . 



1 ._ 3291-7 



2___ , 3288-9 



3 3291-1 



4.. 3286*2 



5 3290-5 



6 _ -_ 3290-0 



7___ 3287*2 



8.. 3286*2 



9 3290*5 



10. _ 3292-8 



11. _ ._ 3286-2 



12.. _ 3282-8 



13. _ 3291-7 



14 3287-2 



15 3292-2 



16 3288-9 



The mean of these values is 3289*0 with a probable error of 

 ±1-9 for a single observation. 



The results are arranged for comparison in the following 

 table : 



Series. Current Density. Mean. Prob. Error of Mean. 



1 -02 3290-7 ±0-7 



II -03 3291-7 ±0-7 



III -04 3291-1 ±1-0 



IV -05 3289-5 ±0-7 

 V -06 3290-0 ±0-6 



VI -07 3289-0 ±0-6 



These results show no dependence upon the current density. 

 In fact, series VI, which differs most from the others, could be 

 slightly increased for the following reason. The day after 

 this series was taken the watch which had been used to measure 

 the time was rated with a clock and found to be gaining at the 

 rate of 2 seconds an hour when lying at the side of the ampere- 

 meter. This was doubtless caused by the magnetic field of the 

 ampere-meter, as the watch at other times was very correct. 



If a connection were applied for this to series IV it would 

 increase it by about one part in 1800, so that it would become 

 3290*6, which is in still closer agreement. During series III, 

 IV, V, which Were taken after this fact had been discovered, 

 the watch was rated and proper connections were applied. 

 But aa the watch had not been rated during series I, II and 

 VI, the corrections cannot be applied to them. 



