360 Profs. J. A Fleming and J. Dewar. On the 



Hence, when the small condenser is under the surface of liquid 

 oxygen its capacity C', as a whole, is 



Kc+O05c, 



and the whole quantity of electricity, Q, given up to the reservoir 

 condenser after n charges of the small one, charged to potential V, 

 have been put into it, is 



Q = 



/~i 



where m = ^ - - - ~ and M = (l ra). 



C + (K + 0-05)c 1 m v 



Again, when the small condenser is lifted out of the liquid oxygen 

 into the gaseous oxygen lying on the surface, its capacity becomes 

 c+0'05c = l*05c, and the whole quantity Q' stored up in the reser- 

 voir condenser, after n charges at a potential V, is 



Q'- 



where m'= - and M' = m (lm' n ). 



C + r05c 1 m 



If in each case the reservoir condenser is discharged through a 

 ballistic galvanometer, the " throw " or elongation of which is pro- 

 portional to the quantity of electricity sent through it, and if and 

 <9' are the throws produced by the quantities Q and Q', we have 



M 



Q ros M 



The ratio Ojtf is given from the observations. 



To solve this equation completely and determine K would be diffi- 

 cult, since the quantity M is a somewhat complicated function of K. 



We know, however, that the ratio of M/M' cannot be very far from 

 unity. A rough experiment had shown that K was a number in the 

 neighbourhood of 1*5, and a calculation shows that when ten dis- 

 charges of the small condenser are made in each case into the large 

 condenser, and if the large condenser has a capacity of 0'5 micro- 

 farad, and the small one a capacity of nearly O001 microfarad, that 

 the ratio M/M' = 1030/1019 nearly. Hence M/M' comes in as a cor- 

 recting factor of about 1 per cent, in value. 



Before relying on the above method, it was necessary to prove that 

 the loss of charge of the small condenser was negligible during the 

 time elapsing between the end of the charge and the end of the dis- 

 charge of the small condenser. 



