172 



Dr. J. Kerr on Measurements 



the values of E were as follows :- 



90 2 

 36x2 2; 



56, 



120 2 



= 56. 



64 x 2* 



The agreement with the first case is more than satisfactory; 

 for if we suppose the true values of Q to be less than the ob- 

 served values by half a unit each, (a difference which lies well 

 within the range of probable error of observation,) the cor- 

 rected values of E rise to 57 and 56*7. 



(3) D = 3. Two measurements were made ; and the values 

 of E were as follows : — 



90 2 



16 x3 2 



= 56, 



120 2 



27 x3 2 



= 59. 



The agreement of these results with each other and with the 

 first case is pretty close, and hardly unsatisfactory; for if we 

 suppose the true value of Q at potential 120 to be greater than 

 the observed value by 1, the corrected value of E falls to 57. 



(4) D = 4. Two measurements were made and verified, with 

 the following results: — 



120 2 nn 150 2 



15x4 



, = 60, 



24x4 



3=58*. 



The agreement with the first case is close, and, indeed, satis- 

 factory; for if we suppose the true values of Q to be greater 

 each by 1 than the observed values, the corrected values of E 

 fall to about 56. 



The uniformity of the electro-optic field was not sensibly 

 perfect in this fourth case, and the increase of D could not 

 safely be carried further. 



21. These numerical results are as trustworthy as any that 

 have yet been obtained on the subject. Taken by themselves 

 also, they afford a sketch of a full proof of the Law of Squares 

 in the actual case of CS 2 . I think it worth while, therefore, 

 to exhibit the contents of the last article in another form, as 

 in the following Table. The calculated values of Q are ob- 

 tained from the equation 



V 2 

 Q= 577D 2 ' 



D measured 



1 



2 



2 



3 



3 



4 



4 





V measured 



60 



90 



120 



90 



120 



120 



150 







63 



36 



64 



16 



27 



15 



24 





Q calculated 



631 



35-5 



63-1 



15-8 



28 



15-8 



246 





