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LIX. A Theory of Galvanic Force. By Professor Challis,F..R.£.* 



HAVING argued in previous communications that the laws 

 of Light, Heat, Gravity, and Electricity may be conse- 

 quences of the dynamic action of an elastic fluid medium, I 

 proceed now to apply the principles of the same theory to the 

 facts of galvanism. As it is hardly possible that so comprehen- 

 sive a theory could escape the contradiction of facts, unless it 

 were well founded, every extension of it to new classes of facts 

 without meeting with contradictions, and without the necessity 

 of new hypotheses, adds greatly to the evidence for its truth. 

 In art. 18 of the " Theory of Electric Force," given in the Oc- 

 tober Number, I have shown that electrical attractions and repul- 

 sions might be explained consistently with hydrodynamic action 

 by the hypothesis of setherial currents. Now it is this very 

 hypothesis which is required for explaining by the same kind of 

 action the laws of galvanism. It must be assumed, on the 

 hydrodynamical theory, that there exist in the neighbourhood of 

 the earth steady setherial currents, which within considerable 

 spaces may be considered to be of uniform velocity and density. 

 By the solution of Problem II., in the " Theory of Attractive 

 Forces" contained in the Philosophical Magazine for No- 

 vember 1859, it appears that these currents would produce no 

 motion of translation of small solid spheres, such as the ulti- 

 mate atoms of bodies are assumed to be. But the same cur- 

 rents might, under the circumstances stated in art. 18 above 

 referred to, give rise to steady secondary currents, which, not 

 being uniform as to velocity and density, might be capable of 

 acting dynamically to a sensible amount on ultimate atoms. 

 That the hypothesis of steady primary currents is also in accord- 

 ance with magnetic phenomena, I hope to show hereafter, and 

 at the same time to consider what may be their origin. • 



1. One of the primary facts of galvanism is its intimate con- 

 nexion with electricity. The following illustration may help 

 to form a distinct idea of the explanation which the hydro- 

 dynamical theory gives of this fact. Conceive any solid sub- 

 stance to be suspended by attachment at one of its points to an 

 immoveable body, and to be acted upon by gravity. Then as- 

 suming it to consist of discrete atoms all equally urged by the 

 force of gravity, the lower superficial atoms must be kept in 

 equilibrium by an excess of molecular attraction above molecular 

 repulsion, and the higher by an excess of molecular repulsion 

 above molecular attraction. Also the force of gravity on any 

 atom in the interior of the body must be just counteracted by 

 the resultant of forces emanating from the atoms. But the 



* Communicated by the Author. 



