301 M. F. Kohlrausch on the Absolute Value of the 



In the present case the above equation is to serve to determine 

 the resistance w ; consequently a second relation is required in 

 order that q may be eliminated. Such a relation is afforded by 

 the currents produced by an earth-induction apparatus when 

 it is quickly turned, in the ordinary way, from one position at 

 right angles to the magnetic meridian into another at 180° 

 from the former. 



Let S denote the superficial area surrounded by the wire of the 

 inductor, and T the earth's horizontal magnetic intensity, then 

 the quantity of electricity traversing each section of the circuit 

 at each such movement, will be 



J 



w 



According to what precedes, this will impart to the needle an 

 angular velocity 7 represented by 



whence we get 





7VK 2 



2 ~" 4§2^2 V AA V 



By equating the two values of q 2 given by (I.) and (II.), we 

 get finally for the resistance of the Inductor + Galvanometer, 

 expressed in absolute measure, 



1 8S 2 T 2 



(VSSi-4 



In order to determine the angular velocity 7, which the 

 separate inductive shocks give to the needle, and the damping \, 

 Weber employs the method of Recoil (Abhandl. der Konigl. 

 Sdchsisch. Gesellsch. der Wissensch. vol. i. p. 349 [1846]), in 

 which inductive shocks in alternately opposite directions are 

 given at every second passage of the needle through its position 

 of equilibrium. If A and B denote the ultimately constant 

 values of the greater and less arcs traversed by the needle 

 swinging under these conditions, we have 



X==1 °g e lv 



B 



1 \ 



7 2 —i - ~vm w 



* Weber, Zur Galvanometrie, pp. 16 et seq. 



