84 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XII.) 



tides, or those of gases and liquids. Hereafter, perhaps, all these modes may appear 

 as the result of one common principle, but at present they require to be considered 

 apart ; and I will now speak of the^r*^ mode, for amongst all the forms of discharge 

 that which we express by the term conduction appears the most simple and the most 

 directly in contrast with insulation. 



^ vii. Conduction, or conductive discharge. 



1320. Though assumed to be essentially different, yet neither Cavendish nor 

 PoissoN attempt to explain by, or even state in, their theories, what the essential dif- 

 ference between insulation and conduction is. Nor have I anything, perhaps, to offer 

 in this respect, except that, according to my view of induction, both it and conduc- 

 tion depend upon the same molecular action of the dielectrics concerned ; are only 

 extreme degrees of one common condition or effect ; and in any sufficient mathematical 

 theory of electricity must be taken as cases of the same kind. Hence the importance 

 of the endeavour to show the connection between them under my theory of the elec- 

 trical relations of contiguous particles. 



1321. Though the action of the insulating dielectric in the charged Leyden jar, 

 and that of the wire in discharging it, may seem very different, they may be asso- 

 ciated by numerous intermediate links, which carry us on from one to the other, 

 leaving, I think, no necessary connection unsupplied. We may observe some of 

 these in succession for information respecting the whole case. 



1322. Spermaceti has been e:[amined and found to be a dielectric, through which 

 induction can take place (1240. 1246.), its specific inductive capacity being about or 

 above 1*8 (1279.), and the inductive action has been considered in it, as in all other 

 substances, an action of contiguous particles. 



1323. But spermaceti is also a conductor, though in so low a degree that we can 

 trace the process of conduction, as it were, step by step through the mass (124/.) ; 

 and even when the electric force has travelled through it to a certain distance, we 

 can, by removing the coercitive (which is at the same time the inductive) force, 

 cause it to return upon its path and reappear in its first place (1245. 1246.). Here 

 induction appears to be a necessary preliminary to conduction. It of itself brings 

 the contiguous particles of the dielectric into a certain condition, which, if retained 

 by them, constitutes insulation, but if lowered by the communication of power from 

 one particle to another, constitutes conduction. 



1324. If glass or shell-lac be the substances under consideration, the same capa- 

 bilities of suffering either induction or conduction through them appear (1233. 1239. 

 1247.), but not in the same degree. The conduction almost disappears (1239. 

 1242.) ; the induction therefore is sustained, i. e. the polarized state into which the 

 inductive force has brought the contiguous particles is retained, there being little 

 discharge action between them, and therefore the insulation continues. But, what 

 discharge there is, appears to be consequent uponJ;hat condition of the particles into 



