234 MICHAEL FARADAY HIS LIFE AND WORKS. 



Lecome excellent conductors when liquefied by heat, and are not decomposed by 

 electiicity with separation of their elements in the same way as aqueous solu- 

 tions. To the list of these compounds Faraday adds that of those substances, 

 eitlier simple, like sulphur and phosphorus, or compound, such as tlje periodides 

 and pcrchlorides of tin, and many others, which continue isolators when fused 

 as well as in the solid state. In tins first investigation, notwithstanding a great 

 number of experiments in which he employed the influence of heat and of elec- 

 tricity of high tension in the study of the conductive power of solid bodies, he 

 did not succeed in determining very accurately the conditions of electrical con- 

 ductibility ; he only ascertained that, with one exception, which he justly 

 regards as only apparent, there is not a solid body which, on becoming conduct- 

 ive by its passage to a liquid state, is not decomposed by the electrical current. 

 We may add, so as not to return to the subject, that Faraday sometimes had 

 doubts upon this point, and that he even thought that water could conduct elec- 

 tricit^' without being decomposed. Now experiment shows that in all cases, 

 even those which appear most favorable to this opinion, electricity cannot be 

 transmitted under any form through a compound liquid body without this body 

 undergoing electro-chemical decomposition. 



As to the causes of conductibility, the}' are still far from being known ; when 

 we see bodies, such as the gases, becoming conductors when greatly rarefied, 

 whilst under the ordinar\^ pressure they are perfect insulators, we are compelled 

 to come to the conclusion that the impossibility that we find of explaining this 

 difference, as well as so many others presented in this respect by solid and 

 liquid bodies, is due to the fact that we have not yet a correct notion of the 

 molecular constitution of bodies. Perhaps the recent theories of several physi- 

 cists, particularl}' that of Clausius, who regards the particles of bodies as being 

 in a constant state of movement, may succeed in elucidating this subject, which 

 is still so m^'sterious. Faraday himself had fully foreseen this relation between 

 electrical conductibility and the ideas which we may form as to the nature of 

 matter. In a remarkable article published in 1844 he showed, upon an experi- 

 mental basis, that in the theory according to Avhich a body is regarded as con- 

 sisting of atoms possessing weight separated from each other by larger or 

 smaller intermolecular intervals, there are a multitude of facts, some of A\hich 

 can only be explained by assuming that the atoms are the conductors and tbe 

 molecular space an insulator, and the others by supposing that the intermole- 

 cular space is the conductor and the atoms insulators — a contradiction which is 

 inadmissible. He concluded from this that we must imagine matter to be con- 

 tinuous, or rather imagine the atoms to be simply centres of force, and conse- 

 quently replace the atomistic by the dynamical tlieory. "We shall often find 

 traces of these ideas in the subsequent works of Faradaj^ ; for ourselves we 

 cannot take this view. We are convinced that it is not by denying tlie exist- 

 ence of matter, properly so called, and admitting only that of forces, that we 

 shall succeed in solving the difficulties under consideration and many others, 

 but rather, following the example of Clausius and others, by modifyiug the 

 ideas hitherto accepted as to the mode of constitution of bodies, and replacing 

 them by others more in accordance with recent discoveries. 



But we must return to electro-chemistry. I have already said that Faraday 

 first occupied himself with chemical decompositions effected by the electrical 

 current. He commences by effecting the decomposition of water and of solu- 

 tions by means of a jet of ordinary electricity, rendered as continuous as possi- 

 ble by leaving a stratum of air interposed between the metallic points which 

 convey and carr}- off the electricity from a machine, and a strip of moistened 

 paper which this electricity traverses. He observes that the deposition of the 

 elements, separated from the decomposed liquid, takes place against the surface 

 of the air which is in contact with the paper. Then, investigating the decom- 

 positions effected by the pile, he examines the various explanations which have 



