248 



Mr. G. W. Walker on tJie 



I have therefore prepared the following numerical table, 

 makino- use cf Leoendre's Tables for K and Hutton^s Tables 

 of Xaperian Logarithms 

 1 cm. 



Throughout I have taken B as 



Xo. 



(1) 1-8 



(2) 1-8 



(3) 1-8 



(4) ^ 

 (5) 

 (6) 3 



b'. 



•98 



•99 



•999 



•9999 



•9999 



•98 



3-0233; 1-5866 

 3-3577J 1-5806 

 4-5006 1-5715 



5-658 

 , 5-658 

 ! 3-0233 



1-570 

 1-570 

 1-5866 



a 



ill 



cms. 



in 

 cms. 



•112 

 •112 

 •112 I 

 -074 ' 

 -0108 

 -0108 



4K, 



1-18 

 1^40 

 213 

 294 

 3-07 

 1-38 



7-60 

 8-48 

 11-2 

 14-4 

 144 



' 



^ 













1 



^ 



-I 



=? 



1 





^o 





»— • 



-^ 



,^-^ £> 



1 



+ 



7 --^^^ 



^^ 



^ 



J '+ 













^: e 





W 



^ 





«» 



« 



M° 



^t, GO 



\'^T 



•333 



2-53 



•291 



2-46 



•213 



2-38 



•143 



206 



•054 



•777 



•101 



-767 



In (!)_, (2), and (3) we observe that keeping the air-gap 

 about 2 mms. the effect diminishes as the breadth of the 

 needle increases. 



In (2) and (6), w^here the breadth is practically the same, 

 we see the diminishing effect of the air-gap as the gap is 

 diminished. At the same time the gap could not practically 

 be reduced to ^ mm., and the variation, although reduced, is 

 still important. I think that this investigation may be held 

 to show^ that the air-gap as usually found in an electrometer 

 is quite sufficient to account for the observed fact that there 

 is a maximum sensibility depending on the potential of the 

 needle ; and the conclusion is that the ordinary formula 

 would be more nearly obeyed with a small air-gap. 



It is of interest to note w^hat difference results when, instead 

 of the potential, the charge of the needle is kept constant. 

 The method already used for finding the mechanical force 

 on the needle will still be valid provided Y3 is reckoned for 

 the displaced position. 



If 0V3 be the potential of the needle in the zero position, 

 we get 



V3 = oV3- ^'6>(V2-Vi) to 1st power of 6. 



CIq 



