(1) 



Oscillations in Coupled Circuits. 29 



in this way, owing to the absence of disturbance by the 

 auxiliary sparking apparatus. 



Some photographs and their measurements are also given 

 for electrical oscillations in coupled circuits produced by the 

 " musical arc' 1 method. 



(1) Calculation of the Potential at the Terminals of the 

 Secondary Condenser. 



The general equations as employed by Drude for two 

 oscillatory circuits, when the coefficient of coupling M 2 /^!^ 

 is not very small, are 



(Tl » + 0/)iLv . + 2(9, ££ + v, =^(17 + e?) d ~^ 



(T,« + 6i) ^ + 29, ±Jf + V, = Pn (Tj> + e,*) g*_, 



where 



fc=*BA, T^ + ^^LA, Pi2 = 2^#, 



# _. 1.13 f< T2i/12_T f( ~ _1 -L 21 Ci 



C7 2 — 2^2^ 2j J-2 nrU2 — .U 2 ^ 2 , ^21= q T n • 



2 Ju 2 ' /£ 



Ri> L 1? Ci,andR 2 » L 2 , C 2 , are the resistances, self-inductances, 

 and capacities in the primary and secondary circuits. 



Drude's results are applicable to the case of a Tesla trans- 

 former, in the secondary of which the current varies from 

 point to point along the wire. In the experiments described 

 in the present paper the two coils were connected to con- 

 densers^ of considerable capacity, so that we may neglect 

 the variation of current along the wires, and in consequence 

 put L 12 = L 21 = M, the mutual inductance of the two cods. 



Vj and 2V 2 are the potential-differences of the plates of the 

 primary and secondary condensers. 



Drude shows that the solution of (1) is 



V j = A^ + A 2 e*to + A 3 ^» + A^ 3r*, 



V 2 = B^' .'/i + B 2 e f y< + B 3 ^3 + B/ ."., 

 where 



y ,= -.8- -r^+iT, y^- 3 - &+&-.T, 



