Researches in Electricity ; Twelfth Series, 427 



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- 

 quired during the previous polarization. The lines of inductive ac- 

 tion which occur in fluid electrolytes are exemplified by employing 

 for that purpose clean rectified oil of turpentine, containing a few 

 minute fibres of very clean dry white silk; for when the voltaic circuit 

 is made by the introduction into the fluid of wires, passing through 

 glass tubes, the particles of silk are seen to gather together from all 

 parts, and to form bands of considerable tenacity, extending between 

 the ends of the wires, and presenting a striking analogy to the 

 arrangement and adhesion of the particles of iron filings between the 

 poles of a horse-shoe magnet. 



* See Lond. and Edinb. Phil. Mag. vol. vi. p. 61. 



