1881.] Mr. J. Hopkinson. Dielectric Capacity of Liquids. 347 



1. The expectancy for the coincidences between two quantities in 

 the second compartment. 



2. The expectancy for the coincidences between one quantity in 

 the first compartment and one in the second. 



Now A is supposed to increase gradually from a value smaller than 



- to a value larger than -L. As long as it is smaller, the result must 



a 2 a 2 



be the same as that we have previously obtained, but none of the 

 quantities which enter into the calculation show any discontinuity, as 



A passes through the value and hence the formula cannot change 



B 



at that point and must be true as far as the value — , or as B may be in 

 the limit equal to we have extended our formula to all values of A 

 smaller than It can be further extended in the same way and 



a 6 



must in fact be true for all values of A. 



V. " Dielectric Capacity of Liquids." By J. Hopkinson, F.R.S. 

 Received January 6, 1881. 



(Abstract.) 



These experiments have for object the determination of the refrac- 

 tive indices and the specific inductive capacity of certain liquids, and 

 a comparison of the square of the refractive index for long waves 

 and the specific inductive capacity. 



In the following table are given the results obtained for refractive 



index for long waves deduced by the formula ja=/i co +— , the square 



A.* 



of /*qq , and the observed values (K) of the specific inductive 

 capacity. 



Petroleum spirit (Field's) T922 1*92 



Petroleum oil (Field's) 2'075 2"07 



(Common) 2-078 2'10 



Ozokerit lubricating oil (Field's) 2*086 2"13 



Turpentine (Commercial) 2*128 2*23 



Castor oil 2-153 478 



Sperm oil 2-135 3-02 



Olive oil 2-131 3-16 



Neatsfoot oil 2*125 3*07 



