RECENT PROGRESS IN PHYSICS. 399 



communication wliicli supervenes in the conducting mass upon the 

 polarizatijon of the particles of. that body, (1675.) 



"16T8. That, therefore, induction can only take place through or 

 across insulators ; that induction is insulation, it being the necessary 

 consequence of the state of the particles and the mode in which the 

 influence of electrical forces is transferred or transmitted through or 

 across such insulating media. 



" 1679. The particles of an insulating dielectric whilst under induc- 

 tion may be compared to a series of small magnetic needles, or more 

 correctly still to a series of small insulated conductors. If the space 

 round a charged globe were filled with a mixture of an insulated 

 dielectric, as oil of turpentine or air, and small globular conductors, 

 as shot, the latter being at a little distance from each other, so as to 

 be insulated, then these would in their condition and action exactly 

 resemble what I consider to be the condition and action of the particles 

 of the insulating dielectric itself. If the globe were charged these 

 little conductors would all be polar ; if the globe were discharged 

 they would all return to their normal state, to be polarized again 

 upon the recharging of the globe. The state developed by induction 

 through such particles on a mass of conducting matter at a distance 

 would be of the contrary kind_, and exactly equal in amount to the 

 force in the inductric globe. There would be a lateral diffusion of 

 force, (1224, 1297,) because each polarized sphere would be in an active 

 or tense relation to all those contiguous to it, just as one magnet can 

 affect two or more magnetic needles near it, and these again a still 

 greater number beyond them. Hence would result the production of 

 curved lines of inductive force if the inducteous body in sucli a mixed 

 dielectric were an uninsulated metallic ball, or other properly shaped 

 mass. Such curved lines are the consequences of the two electric 

 forces arranged as I have assumed them to be ; and that the inductive 

 force can be directed in such curved lines is the strongest proof of the 

 presence of the two powers and the polar condition of the dielectric 

 particles. 



"1680. I think it is evident, that in the case stated, action at a 

 distance can only result through an action of the contiguous con- 

 ducting particles. There is no reason why the inductive body should 

 polarize or affect distant conductors and leave those near it, namely, 

 the particles of the dielectric, unaffected ; and everything in the form 

 of fact and experiment with conducting masses or particles of a suita- 

 ble size contradicts such a supposition." 



As a consequence of the above, Faraday supposes all bodies to consist, 

 as it were, of small conductors which are separated by an insulating 

 substance ; the inductive action of one particle on another, he must 

 also assume, to be precisely like induction between two conductors, as 

 generally supposed ; he must then assume action at a distance of the 

 ordinary kind between each two particles of the insulator. Since he 

 must assume this at last, and an insulating interval, there is really 

 little reason to set aside the accepted opinions which, though they 

 may have many deficiencies, must be maintained until overwhelming 

 -proof establishes not only their insufficiency, but their incorrectness 

 also. 



In continuation of the fourteenth series, Faraday notices the indue- 



