50 



those at a distance, and which comprehend the phenomena of the 

 electric discharge. Having considered, in the preceding paper, the 

 process by which the former condition is estabHshed, and which con- 

 sists in the successive polarization of series of contiguous particles 

 of the interposed insulating dielectric ; the author here proceeds to 

 trace the process, which, taking place consequently on simple in- 

 duction, terminates in that sudden, and often violent interchange of 

 electric forces constituting disruption, or the electric discharge. He 

 investigates, by the application of his theory, the gradual steps of 

 transition which may be traced between perfect insulation on the 

 one hand, and perfect conduction on the other, derived from the 

 varied degrees of specific electric relations subsisting among the par- 

 ticular substances interposed in the circuit : and from this train of 

 reasoning he deduces the conclusion that induction and conduction 

 not only depend essentially on the same principles, but that they 

 may be regarded as being of the same nature, and as differing merely 

 in degree. 



The fact ascertained by Professor Wheatstone, that electric con- 

 duction, even in the most perfect conductors, as the metals, requires 

 for its completion a certain appreciable time, is adduced in corrobo- 

 ration of these views ; for any retardation, however small, in the 

 transmission of electric forces can result only from induction ; the 

 degree of retardation, and, of course, the time employed, being pro- 

 portional to the capacity of the particles of the conducting body for 

 retaining a given intensity of inductive charge. The more perfect 

 insulators, as lac, glass and sulphur, are capable of retaining electri- 

 city of high intensity ; while, on the contrary, the metals and other 

 excellent conductors, possess no power of retention when the in- 

 tensity of the charge exceeds the lowest degrees. It would appear, 

 however, that gases possess a power of perfect insulation, and that 

 the effects generally referred to their capacity of conduction, are 

 only the results of the carrying power of the charged particles either 

 of the gas, or of minute particles of dust which may be present in 

 them : and they perhaps owe their character of perfect insulators to 

 their peculiar physical state, and to the condition of separation 

 under which their particles are placed. The changes produced by 

 heat on the conducting power of different bodies is not uniform; for 

 in some, as sulphuret of silver and fluoride of lead, it is increased ; 

 ■while in others, as in the metals and the gases, it is diminished by 

 an augmentation of temperature. 



One peculiar form of electric discharge is that which attends elec- 

 trolyzation, an effect involving previous induction; which induction 

 has been shown to take place throughout linear series of polarized 

 particles, in perfect accordance with the views entertained by the 

 author of the general theory of inductive action. The peculiar fea- 

 ture of this mode of discharge, however, is in its consisting, not in 

 a mere interchange of electric forces at the adjacent poles of con- 

 tiguous particles, but in their actual separation into their two con- 

 stituent particles; those of each kind travelling onwards in contrary 

 directions, and retaining the whole amount of the force they had ac- 



