On Transient Electric Current from Iron and Nickel. 123 



As far as terms of the order c -( 2 »+ 10 ) inclusive, — wJJP n ^ A dSi 

 is made up of the term 



4tto 2 » +4 W f 1 (n + 2)H 2 (n + 2) 2 (n + 3)H 4 

 c 2 rt+4 1 2 ! + 3 ! c 2 + 4 ! 2 ! c 4 



+ 2) 2 ^ + 3) 2 (n + 4) 2 Z> 6 

 5 ! 3 ! c 6 



+ ...}, 



due to the images P and Q, together with the term 

 27ra 2n + 4 a 3 b 6 u 2 



c 2n+10 > 



due to the image P. 



By interchanging m and n, u and v 3 a and b, the remaining 

 term on the right-hand side of (10) can be found. 



If the vibrating spheres consist of liquid of density p', the 

 velocity-potential within X is «P n r B /na n_1 , and the kinetic 



energy of the sphere X is (£) .-.y A similar expression 



holds for the other sphere. 



When c is constant the principal term in the expression of 

 the stress between the spheres varies as c ~ (m+n+2) or as c~^ 2n+5 \ 

 or as c~ (2m+5) . 



If u, v are simple harmonic functions of the time, the 

 average stress between the spheres is to be found as before. 



The case when m—n=l has been discussed by Mr. Hicks 

 (loc. cit.) ; for all other values of m and n the centres of the 

 spheres are at rest. 



X. On Transient Electric Current produced by suddenly twist- 

 ing Magnetized Iron and Nickel Wires. By H. Nagaoka, 

 Rigakusi, of Imperial University, Tokyo*. 



[Plate II.] 



IN a recent number of Wiedemann's Annalen, Herr 

 Zehnderf communicated the result of his experiments 

 on the transient current produced by twisting magnetized iron 

 and nickel wires, in which he finds the direction of current in 

 nickel to be opposite to that in iron. The same result had been 

 already known to me since July 1888. Being engaged in 



* Communicated by Sir William Thomson. 



t " Ueber Deformationsstrome." Wiedemann's Annalen, Bd. xxxviii. 

 p. 68. This number reached me on 14th October, 1889. 



