308 HENRY A. EOWLAJSTD 



is in r" so that we can make r" = 0, the value of l 2 L t c" will be inde- 

 terminate and we can find J f by the adjustment of W alone. 



i C 



This is an excellent method, apparently, as only one adjustment is 

 required. 

 However, see the remarks on method 15. This present method 



r" = for is Anderson's with, however, alternating currents instead 



C 



of direct as in his. 



The other two values are imaginary in this case. Indeed the whole 



method, B, is only of special value for , as two adjustments are needed 



c 



for the others. 



Method 17. 

 (A) TF=oo. 72=00 



VML'= R t R" - R tl R 

 L' 



By this method the self induction of the mutual induction coil is 

 eliminated. But it is difficult to apply, as two resistances must be 

 adjusted and the adjustment will only hold while the current period 

 remains constant. The same remarks apply to B and C following. 



(B) R=>. 



,+ R" + #] + (R + JB,) (R" 



M~ RW 



x> 



L' _ R (R + R, + R" + #) + (K + #,) (R" 

 M~ RR tl 



Method 18. 

 R t R" - R'R tl = 



L ' - i L R " a. R' + R" 

 W'~ *"%, ~W^~ 



L' and M' belong to the same coil. By adjusting the Wheatstone 

 bridge first, W can then be afterwards adjusted. 



