﻿between Electrified and Magnetized Bodies. 369 



kinds of force, although originating in such different circum- 

 stances, are all modes of action of steady currents of the cetherial 

 medium. This general result gives the means of accounting at 

 once, on hydrodynamical principles, for the mutual action, ob- 

 served by Oersted, between the rheophore of a galvanic circuit and 

 a magnetized needle. (See art. 18 of the "Theory of Galvanic 

 Force" in the Philosophical Magazine for December 1860, and 

 'Principles of Physics/ pp. 611 & 612) But the same result 

 points to a mutual action between an electrified body and a mag- 

 netized body. I have, in fact, indicated in art. 18 of the com- 

 munication in the Philosophical Magazine for October 1860, that 

 the setherial currents which account for electric force and those 

 which account for magnetic force are generated under like cir- 

 cumstances ; that is, in both cases a gradation of the interior 

 density of the substance gives rise, in consequence of the earth's 

 motion through the sether, to secondary setherial streams. There 

 is, however, the difference that whereas the gradation of density- 

 is maintained in the electrified body by intei'ior molecular action 

 due to the abnormal state into which its superficial atoms are 

 put either by friction or by induction, in the magnetized body 

 the gradation of density results from interior molecular action 

 which is independent of the state of the superficial atoms. 



From the above statements it will appear that I had reason 

 from theory to expect that, by the intervention of the electric 

 and magnetic currents, there would be, between an electrified 

 body and a magnetized body, a mutual action which might be ex- 

 perimentally recognized. Now, although I do not undertake to 

 assert that no experimental evidence of such action existed, I 

 may say that I did not succeed in finding any, and that I failed 

 to discover in Faraday's experiments any criterion for settling 

 the question. I did not, however, consider this to be a fatal 

 objection to my theory of the physical forces, because at the same 

 time that the theory lacked this confirmation, there appeared to 

 ])£ no experimental evidence of a directly contradictory kind. 

 ' But now, at length, I am able to appeal to appropriate expe- 

 riments. Those made by Mr. Vincent, " On the Relations of 

 Magnetism and Static Electricity," the details of which are given 

 in the April Number of this Magazine, bear directly on the 

 question raised by the theory. It seems that these experiments 

 fully establish the fact of mutual action between e]ectrified and 

 magnetized bodies, and thus confirm the theory. My object in 

 making this brief communication is fulfilled by pointing to this 

 confirmation, which I think I may regard as an important corro- 

 boration of my general theory of the physical forces. 



Cambridge, April 14, 1871. 



