674  Mr.  Gr.  B.  Dyke  on  the  Use  of  the  Cymometer 
If  h-2   is  calculated  from  the  formula 
./_E/Xl0n 
R'  =  7-2^,     Lx= 768000  cms.,     ?^  =  '95  x  106, 
we  get  cy  =  *025. 
Hence  0  . 
mean  o2  ="022. 
From  fig.  2  (a)  we  see 
J,.  =  '164  amps. 
J/  =  -104  amps. 
y-,  =  1-53. 
Calculating  S2  from  the  formula 
S'X' 
8.= 
(j?)"' 
we  get  S2  =  *022. 
Hence 
mean  value  of  &i=i{(X-Sj)  +  (X'-8,— 8,')} 
=  •077. 
Now  the  decrement  8  of  the  ammeter  joer  se  is  given  by 
the  formula 
R  x  109 
4^    ' 
where  R=3'5ot,     Li =708000  cms.,     ^='95  x  106. 
8=-012. 
Hence  decrement  of  cymometer  per  se 
=  S2-S 
=  -022--012  =-010. 
Passing  to  the  primary  circuit,  we  had  the  formula 
4!!jL81_ 
109 
for  the  spark  resistance  r  ;  where 
L=5000  cms.,     ^  =  -077,     ^='95  X  10G. 
