RELATION OP THE ELECTRIC AND MAGNETIC FORCES. 279 



1733. I have already expressed a hope of finding an effect or condition which shall 

 be to statical electricity what magnetic force is to current electricity (1658.) If I 

 could have proved to my own satisfaction that magnetic forces extended then* in- 

 fluence to a distance by the conjoined action of the intervening particles in a manner 

 analogous to that of electrical forces, then I should have thought that the lateral ten- 

 sion of the lines of inductive action (1659.), or that state so often hinted at as the 

 electro-tonic state (1661. 1662.), was this related condition of statical electricity. 



1734. It may be said that the state of no lateral action is to static or inductive force 

 the equivalent of magnetism to current force ; but that can only be upon the view 

 that electric and magnetic action are in their nature essentially different (1664.). If 

 they are the same power, the whole difference in the results being the consequence 

 of the difference of direction^ then the normal or undeveloped state of electric force 

 will correspond with the state of no lateral action of the magnetic state of the force ; 

 the electric current will correspond with the lateral effects commonly called magnetism : 

 but the state of static induction which is between the normal condition and the current 

 will still require a corresponding lateral condition in the magnetic series, presenting 

 its own peculiar phenomena ; for it can hardly be supposed that the normal electric 

 and the inductive or polarized electric condition can both have the same lateral re- 

 lation. If magnetism be a separate and a higher relation of the powers developed, 

 then perhaps the argument which presses for this third condition of that force would 

 not be so strong. 



1735. I cannot conclude these general remarks upon the relation of the electric and 

 magnetic forces without expressing my surprise at the results obtained with the cop- 

 pier plate (1721. 1725.). The experiments with the flat helices represent one of the 

 simplest cases of the induction of electrical currents (1720.) ; the effect, as is well 

 known, consisting in the production of a momentary current in a wire at the instant 

 when a current in the contrary direction begins to pass through a neighbouring pa- 

 rallel wire, and the production of an equally brief current in the reverse direction 

 when the determining current is stopped (26.). Such being the case, it seems very 

 extraordinary that this induced current which takes place in the helix A when 

 there is only air between A and C (1720.) should be equally strong when that 

 air is replaced by an enormous mass of that excellently conducting metal copper 

 (1721.). It might have been supposed that this mass would have allowed of the form- 

 ation and discharge of almost any quantity of currents in it, which the helix C was 

 competent to induce, and so in some degree have diminished if not altogether pre- 

 vented the effect in A : instead of which, though we can hardly doubt that an infinity 

 of currents are formed at the moment in the copper plate, still not the smallest dimi- 

 nution or alteration of the effect in A appears. Almost the only way of reconciling 

 this effect with generally received notions is, as it appears to me, to admit that ma- 

 gnetic action is communicated by the action of the intervening particles (1729. 1733.). 



1736. This condition of things, which is very remarkable, accords perfectly with 



