ELECTRICITY. 



13 



other matter, or some specific ingredient 

 in that matter, with a force following the 

 same law of the inverse square of the 

 distance ; that this fluid is dispersed 

 through the pores of bodies, and from 

 some unknown peculiarity, can move 

 through them with various degrees of 

 facility, according as they are conduc- 

 tors or non-conductors. Bodies are 

 said to be in their natural state with 

 regard to electricity, when the repulsion 

 of the fluid they contain for a particle 

 of fluid at a distance is exactly balanced 

 by the attraction of the matter in the 

 body for the same particle. In this 

 state they may be considered as satu- 

 rated with the electric fluid. Whenever 

 they contain a quantity of fluid greater 

 than this, they are said to be positively 

 electrified, or to have positive electricity. 

 When, on the other hand, there is a 

 quantity less than that required for satu- 

 ration, the body is said to be negatively 

 electrified, or to' have negative electricity. 

 In the former case, it is the fluid that is 

 redundant, or in excess ; in the latter, 

 it is the matter which is left unsaturated 

 that should be considered as the redun- 

 dant principle. The state of positive 

 electricity, then, consists in a redun- 

 dance of fluid, or in matter that is over- 

 saturated, as it has been termed ; that 

 of negative electricity, in a deficiency of 

 fluid, or in matter under-saturated, or, 

 what is an equivalent expression, in 

 redundant matter. In mathematical 

 language, the former condition may be 

 expressed by the sign plus ; the latter 

 by that of minus. In considering the 

 mutual electrical actions of bodies, the 

 portions in which the matter and the 

 fluid mutually saturate each other, need 

 not be taken into account, since their 

 actions, as we have seen, are perfectly 

 neutralized : and we need only attend to 

 those of the redundant fluid and the 

 redundant matter. 



(50.) When a body contains more 

 than its natural proportion of electric 

 fluid, the surplus will, by the repulsive 

 tendency of its particles, overflow and 

 escape, if such escape be allowed, until 

 the body is reduced to its neutral state. 

 When under- saturated, the redundant 

 matter will attract fluid from all quar- 

 ters from which it can receive it, until it 

 is again brought to its neutral state. 

 This efflux, or influx, is prevented either 

 when the body is surrounded on all 

 sides by substances, through the pores 

 of which the fluid cannot pass, or when 

 the body itselt' is of that nature. 



(51.) The mutual recession of two 

 positively electrified bodies is a direct 

 consequence of the repulsion of the re- 

 dundant fluids contained in each, which, 

 being attached to the matter by their 

 attraction for it, impel it in the direction 

 of their own repulsion. In the same 

 way the mutual approximation of two 

 bodies in opposite electrical states is the 

 immediate effect of the attraction of the 

 redundant fluid in the one, for the redun- 

 dant matter in the other ; and vice 

 versa, for this attraction is mutual. 



(52.) A difficulty does, indeed, occur 

 when we attempt to apply the theory to 

 the case of two bodies which are both in 

 a state of negative electricity, that is, in 

 which there exists in boih certain quan- 

 tities of matter unsaturated with electric 

 fluid. What action does the theory, as 

 hitherto stated, point out as the result in 

 this particular case ? Plainly none. All 

 those portions of the matter of each 

 body which are still saturated, together 

 with the fluid which saturates them, 

 can have, as we have already seen, no 

 effect either of attraction or repulsion. 

 The only active element is the unsatu- 

 rated matter ; but the hypothesis does 

 not assign any action of this matter 

 upon other matter at a distance. Yet 

 we learn from experience that the bodies, 

 under these circumstances, actually 

 repel one another. In order, therefore, 

 to render the hypothesis conformable to 

 fact, we are obliged to annex to it ano- 

 ther condition ; namely, that the parti- 

 cles of simple matter, that is, of matter 

 uncombined with the electric fluid, exert 

 a repulsive action on one another. It 

 is singular that so acute a mind as that 

 of Franklin should not have discerned 

 this defect in his own theory, or perceived 

 that this further condition was abso- 

 lutely requisite for the explanation of 

 the phenomena. Without it, indeed, we 

 should be unable to explain the want of 

 action between two neutral bodies ; for 

 the repulsion of the fluids in both bo- 

 dies being balanced by the attraction of 

 the fluid in the one for the matter in the 

 other, the remaining attraction of the 

 fluid in the second body for the matter 

 in the first would be uncompensated by 

 any repulsion, and the forces would not 

 be held in equilibrium, as we find they 

 really are. 



(53.) The law of electrical induction 

 is an immediate consequence of the 

 Franklinian theory. When a body 

 charged with electricity is presented to 

 a neutral body, the redundant fluid of 



