54 Louis Schwendler— On the General [No. 2, 



I, i. e. for which A' = o, then if c' varies 8c', we have A' = n' 8c', while N' 

 becomes N' + Si\T'. 

 Thus we have 



n' 8c' 



8' = 



JST + 8N' 



E'n' 



f (b' + d") 

 but as a + A + „j- \_ -,, , ,> = p' the complex resistance in Station I, and 



as further 8c' can be neglected against c, we have finally : 



8' = E' n ' 8 °' 



f'+b' + d'c' + p 



Further n', the force exerted by the coil b' on a given magnetic pole 

 when the unit current passes through the coil, can be expressed as follows : 



n' = / \/T'* 

 where / is a coefficient depending only on the dimensions and shape of the 

 coil, on the manner of coiling the wire, and on the integral distance of the 

 coil from the magnetic pole acted upon. 



Thus|we have 



sr = m r ' ^ . So ' =JE\ w. & 



V +f + d' c' + p' 



Now supposing the factor W constant,f iS' becomes smaller the 

 smaller 6 is. 



In the second part it has been proved quite generally that 6 decreases 

 permanently with increasing p' p", no matter to what special cause the vari- 

 ation of c' is due, whence again it follows that p should be a maximum. 



From the form of p however we see that for any given sum b + f + d, 

 p becomes largest if 



f=l + d 

 which is " tlie regularity condition" of the differential method. 



* This expression supposes that the thickness of the insulating covering of the wire 



can be neglected against the diameter of the wire, which is allowable, r' is a constant 



with respect to V. 



f 

 f That W can be kept constant while 6' decreases and — ■ varies, and f+lf+ cV 



is constant, it will be clear is possible, for if d' > o the variation of V + cV may be 

 considered entirely due to a variation of d', equal and opposite in sign to the variation 

 of /'. If d' = o then we must consider r' variable with V in order to keep W constant 



while - varies, which is admissible since the position of the coils has not been fixed as 

 yet. 



