Oy ELECTRICITY IN EQUILIBRIUM. 659 



practical part of electricity, and to examine the natural and artificial appara- 

 tus concerned in electrical phenomena, as well as in those effects, which 

 have been denominated galvanic. 



It is supposed that a peculiar ethereal fluid pervades the pores, if not the 

 actual substance, of the earth and of all other material bodies, passing through 

 thfm with more or less facilit}', according to their different powders of conduct- 

 ing it: that the particles o: this fluid repel each other, and are attracted by 

 the particles of common matter: that the particles of common matter also 

 repel each other: and that these attractions and repulsions are equal among 

 themselves, and vary inversely as the squares of the distances of the particles. 



The effects of this fluid are distinguished from those of all other substances 

 by an,attractive or repulsive quality, which it appears to communicate ta 

 different bodies, and which differs in general from other attractions and 

 repu sions, by its immediate diminution or cessation, when the bodies,acting on 

 each other, come into contact, or when they are touched by other bodies. 

 The pame electricity is derived from electrum, amber; for it was long ago 

 observed that amber, when rubbed, continues for some time to attract small 

 bodies ; but at present electricity is usually excited by other means. In 

 general a body is said to be electrified, when it contains, either as a whole, or 

 in any of its parts, more or less of the electric fluid than is natural to it; and it is 

 supposed that what is called positive electricity depends on a redundancy, 

 and negative electricity on a deficiency of the fluid. 



These repulsions and attractions are supposed to act, not only between two 

 particles which are either perfectly or very nearly in contact with each other, 

 but also between all other particles at all distances, whatever obstacles may 

 be interposed between them. Thus, if two electrified balls repel each other, 

 the effect is not impeded by the interposition of a plate of glass: and if any 

 other substance interposed appears to interfere with their mutual action, it 

 is in consequence of its own electrical aflections. In these respects, as well 

 as in the law of their variation, the electrical forces differ from the common 

 repulsion which operates between the particles of elastic fluids, and resemble 

 more nearly that of gravitation. Their intensity, when separately consider- 

 ed, is much greater than that of gravitation, and they might be supposed 



