20 Mr. S. U. Pickering on the Theory of 



induction. It will be sufficient to carry out the transformation 

 for one of the components : — 



d&_ dG 



dy dz 



da db dc, 



r 

 ^jjj da db dc ; 



and, finally, remembering that 



dv dw 



Similarly, 



-JJ 



dc db ' 



rnw — nv 



m, 



'8-r 



d$. 



— DHL n 



c= i do. 



Z, m, u are the normals drawn to the inside of each medium. 

 The surface integration must be carried out on both sides of a 

 surface at which u, v, w are discontinuous. 



I do not know whether these equations will ever really 

 simplify the investigation of an actual problem, but it seems 

 of interest to know that we can always express the magnetic 

 forces due to steady currents in a conductor, in terms of the 

 values of the currents at the surface of the conductor ; the 

 components of the currents inside may be unknown, though 

 of course they are determined by the surface values. 



III. The Tlieory of Dissociation into Ions, and its Consequences* 

 By Spencer Umfreville Pickering, M.A., F.R.S.* 



THE supporters of the present physical theory of solution 

 hold that the majority of salts, acids, and bases, when 

 dissolved in a large excess of water, are entirely resolved into 

 their component ions. That the facts of the case warrant such 

 Communicated by the Physical Society : read March 20, 1891. 



