276 ELECTRICAL INDUCTION. SECT. XXV11I. 



However, the law of the repulsive force is liable to great 

 disturbance from inductive action, which Mr. Snow Har- 

 ris has found to exist not only between a charged and 

 neutral body, but also between bodies similarly charged, 

 and that in the latter case the inductive process may be- 

 indefinitely modified by the various circumstances of the 

 quantity and intensity of the electricity, and the distance 

 between the charged bodies. Since electricity can only 

 be in equilibrio from the mutual repulsion of its par- 

 ticles, which according to these experiments varies in- 

 versely as the square of the distances, its distribution in 

 different bodies depends upon the laws of mechanics, 

 and therefore becomes a subject of analysis and calcula- 

 tion. Although the distribution of the electric fluid has 

 employed the eminent analytical talents of M. Poisson 

 and Mr. Ivory, and though many of their computed 

 phenomena have been confirmed by observation, yet 

 recent experiments show that the subject is still involved 

 in much difficulty. Electricity is entirely confined to 

 the surface of bodies ; or if it does penetrate their sub- 

 stance, the depth is inappreciable ; so that the quantity 

 bodies are capable of receiving does not follow the pro- 

 portion of their bulk, but depends principally upon the 

 form and extent of surface over which it is spread : thus 

 the exterior may be positively or negatively electric, 

 while the interior is in a state of perfect neutrality. 



It appears from the experiments of Mr. Snow Harris, 

 that a given quantity of electricity divided between two 

 perfectly equal and similar bodies, exerts upon external 

 bodies only one-fourth of the attractive force apparent 

 when disposed upon one of them ; and if it be distrib- 

 uted among three equal and similar bodies, the force is 

 one-ninth of that apparent when it is disposed on one of 

 them. Hence if the quantity of electricity be the same, 

 the force varies inversely as the square of the surface 

 over which it is disposed ; and if the surface be the same, 

 the force varies directly as the square of the quantity 

 of the electric fluid. These laws however do not hold 

 when the form of the surface is changed. A given 

 quantity of electricity disposed on a given surface has the 

 greatest intensity when the surface has a circular form, 

 and the least intensity when the surface is expanded 



