112 Mr. L. Scliwendler on the General Theory 



and 



we have 



-s fcv) <»•■•> 



A' 

 Therefore S' approximates most rapidly* towards zero if — py/ 



does ; or we have 



" — ~TTl > 



my' 



which should be as small as the circumstances will allow of. 

 Now that D' approximates also rapidly towards zero by making 



m'yjr' 



as small as possible can be proved as follows : — 

 By definition we have 



D'= t. 



Further, as <£' = i|r' (on account of the key equation), we have 

 y=S ; invariably, 



. . V - p , 



Thus D' for any given P' approximates towards zero at the 

 same rate as S' does, i. e. the smaller 6' becomes. 



Therefore the whole problem is actually most generally solved 

 by making 



m-yr 

 as small as possible for both stations. 



Now for station I., if balance in the g 1 branch for the outgoing 

 current be established, we have 



where c 1 is the "measured circuit" from station I.; and suppo- 

 sing that all variations in the system are chiefly due to variations 



* — — can never become zero, but should, on the contrary, be as large 

 as possible ; and therefore S' can only approximate towards zero by 

 becoming as small as possible. 



