SECT, xxvin.] ELECTRICAL FORCES. 313 



electricity, approaches it, that the mutual repulsion of the 

 particles of the electric fluid diminishes the pressure of the 

 fluid on the air on the adjacent sides of the two bodies, and 

 increases it on their remote ends ; consequently, that equili- 

 brium will be destroyed, and the bodies, yielding to the 

 action of the preponderating force, will recede from or repel 

 each other. When, on the contrary, they are charged with 

 opposite electricities, it is alleged that the pressure upon the 

 air on the adjacent sides will be increased by the mutual 

 attraction of the particles of the electric fluid, and that on 

 the further sides diminished; consequently, that the force 

 will urge the bodies towards one another, the motion in both 

 cases corresponding to the forces producing it. An attempt 

 has thus been made to attribute electrical attractions and 

 repulsions to the mechanical pressure of the atmosphere. 

 It is more than doubtful, however, whether these phenomena 

 can be referred to that cause ; but certain it is, that, what- 

 ever the nature of these forces may be, they are not impeded 

 in their action by the intervention of any substance what- 

 ever, provided it be not itself in an electric state. 



A body charged with electricity, although perfectly insu- 

 lated, so that all escape of electricity is precluded, tends to 

 produce an electric state of the opposite kind in all bodies 

 in its vicinity. Positive electricity tends to produce negative 

 electricity in a body near to it, and vice versd, the effect being 

 greater as the distance diminishes. This power which elec- 

 tricity possesses, of causing an opposite electrical state in its 

 vicinity, is called induction. When a body in either electric 

 state is presented to a neutral one, its tendency, in conse- 

 quence of the law of induction, is to disturb the electrical 

 condition of the neutral body. The electrified body induces 

 electricity contrary to its own in the adjacent part of the 

 neutral one, and therefore an electrical state similar to its 

 own in the remote part. Hence the neutrality of the second 

 body is destroyed by the action of the first, and the adjacent 

 parts of the two, having now opposite electricities, will attract 



