38 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XI.) 



forced one, for it is originated and sustained only by force, and sinks to the normal 

 or quiescent state when that force is removed. It can be continued only in insulators 

 by the same portion of electricity, because they only can retain this state of the par- 

 ticles (1304.). 



1299. The principle of induction is of the utmost generality in electric action. It 

 constitutes charge in every ordinary case, and probably in every case ; it appears to 

 be the cause of all excitement, and to precede every current. The degree to which 

 the particles are affected in this their forced state, before discharge of one kind or 

 another supervenes, appears to constitute what we call intensity. 



1300. When a Leyden jar is charged, the particles of the glass are forced into this 

 polarized and constrained condition by the electricity of the charging apparatus. 

 Discharge is the return of these particles to their natural state from their state of 

 tension, whenever the two electric forces are allowed to be disposed of in some other 

 direction. 



1301. All charge of conductors is on their surface, because being essentially induc- 

 tive, it is there only that the medium capable of sustaining the necessary inductive 

 state begins. If the conductors are hollow and contain air or any other dielectric, 

 still no charge can appear upon that internal surface, because the dielectric there 

 cannot assume the polarized state throughout, in consequence of the opposing actions 

 in different directions. 



1302. The known influence oi form is perfectly consistent with the corpuscular 

 view of induction set forth. An electrified cylinder is more affected by the influence 

 of the surrounding conductors (which complete the condition of charge) at the ends 

 than at the middle, because the ends are exposed to a greater sum of inductive 

 forces than the middle ; and a point is brought to a higher condition than a ball, be- 

 cause, by relation to the conductors around, more inductive force terminates on its 

 surface than on an equal surface of the ball with which it is compared. Here too, 

 especially, can be perceived the influence of the lateral or transverse force (129/.), 

 which, being a power of the nature of or equivalent to repulsion, causes such a dis- 

 position of the lines of inductive force in their course across the dielectric, that they 

 must accumulate upon the point, the end of the cylinder, or any projecting part. 



1303. The influence of distance is also in harmony with the same view. There is 

 perhaps no distance so great that induction cannot take place through it* ; but with 

 the same constraining force (1298.) it takes place the more easily, according as the 

 extent of dielectric through which it is exerted is lessened. And as it is assumed by 

 the theory that the particles of the dielectric, though tending to remain in a normal 

 state, are thrown into a forced condition during the induction ; so it would seem to 



* I have traced it experimentally from a ball placed in the middle of the large cube formerly described 

 (1173.) to the sides of the cube six feet distant, and also from the same ball placed in the middle of our large 

 lecture-room to the walls of the room at twenty-six feet distance, the charge upon the ball in these cases being 

 solely due to induction through these distances. 



