1884.] measurement of the capacity of a condenser. 



181 



121 



Mean time of a vibration = -^ sec. 



98 



Thus 



2N +®*- = jy . 



.32 — lOI 64 



The lower sign is the one to be taken. 



Putting N s for the frequency of the standard fork, we get in 

 the same way the equations : 



2 % + m = N <*> 



19 



4 -^0 ~ Tfti = N s (temperature = 20° C). 



Now (Rayleigh, Phil. Trans. I. 1883) 



N s = 128-140 {1 - (t - 16) x -00011}. 

 Hence N s = 128-0836, 



N^= 32-10005, 



N 6i = 64-2083, 

 N S2 = 32-5091. 

 Substituting our resistances in Thomson's formula, we have 



nC= c ± d{ 1 + m) ' nearly > 



_ 99 _a 

 "TOO cd' 

 the resistances being in C.G.S. units. 



Now the B.A. unit is, as determined by Lord Rayleigh, 



•987 x 10 9 . 

 Hence, if our resistances are in B.A. units, we have 



r _l 99 1 a 



n ' 100 ; 987 x 10 9 ' cd' 



The results obtained are given in the following table : 



