chap. xiii.j CHRISTIANAS COMPENSATOR. 



141 



screws to I and iv, o is connected to the resistance 



box, and the resistance box with wx, the unknown 



resistance, which is attached on the other side to n. 



The galvanometer G is connected with the platinum 



wheel of the compensator through 



the binding screw connected with 



in, and on the other side to s, 



the binding screw on the re- 



sistance box, from which also 



a wire proceeds to Vfx. Thus 



Wheatstone's bridge is formed. 



The needle of the galvanometer 



G is brought to zero by equalising 



the potentials at in and s, 



effected by turning the disc of Fig. 73,-Aramgement of 

 the round compensator, just as the Modified Com- 

 the position of the slider of the 

 long compensator is altered for the same purpose. 



Then, just as in the long compensator, wx : R/t : : 



the distance between I and in : the distance between 



in and iv. Call the distance between I and in w,, 



and the distance between in and iv W 2 , then wx : nh 



: : w : W or 



\v.r 



. 



[The student will be able to follow the comparison, 

 with Wheatstone's bridge (Fig. 71) if he observes that 

 \vx of Fig. 73 = r of Fig. 71, nh = Re, the distance 

 between I and ill (w,) = the distance between A and s, 

 and the distance between in and iv (w^) = the dis- 

 tance between s and B.] 



Now, wx, the unknown resistance, may be a coil 

 of wire, a galvanometer, a piece of muscle or nerve, 

 it does not matter what. The method described is 

 applicable to all, and equally applicable for the de- 

 termination of the resistance of different parts of the 



