MICHAEL FAEADAY — HIS LIFE AND WORKS. 233 



hv liim upon these questions until after the exposition of liis works on electricity 

 and magnetism. We must, however, at once admit that his views on these mat- 

 ters are very contestable, and that, if they inspired him to make experimental 

 researches of the highest interest, this is a proof that, in the hands of a man of 

 genius, even a bad theory may be the origin of the most beautiful discoveries. 



II. I pass now to the examination of those works of Faraday which relate 

 to electricity and magnetism. It is not without embarrassment that I approach 

 this examination ; for these researches are so numerous that it would be neces- 

 sary to extend this notice beyond all bounds in order to give only a simple 

 analysis of them ; and they are at the same time so varied that it is impossible 

 to explain them in the chronological order of their publication without confusion 

 being the result. Thus, for example, the researches on induction are interrupted 

 liy odiers on electro-chemical decompositions, to be afterwards resumed and com- 

 pleted. Each memoir certainly forms a complete whole ; but one memoir is 

 most frequently followed by another the subject of which is quite different. It 

 seems as if the author, after having treated one question, found it necessary to 

 recollect himself before resuming it, and to divert his mind from it, so to speak, 

 by taking up some other kind of work. 



It has, therefore, appeared to me that the best thing for me to do was to group 

 all these various works under a few distinct heads, so as to be able to give their 

 essence without requiring to enter into too many details. The first would include 

 all the researches relating to electro-chemistry ; the second those which have for 

 their object induction, whether electro-dynamic or electro-static ; and the third the 

 phenomena relating to the action of magnetism and dynamic electricity upon light 

 and upon natural bodies in general. It is true that there are some w^orks which 

 elude this classification, as they will not enter into an})- one of our three divisions. 

 But these are less important works, and such as were produced as occasions 

 offered : that is to say, they are the fruit of some particular circumstance which 

 attracted Faraday's attention to some special point. Such is, for example, the 

 memoir which has for its object the investigation of the electrical properties of 

 the G-i/nuiofKS — and that devoted to the evolution of electricity by the friction 

 exerted against solid bodies by the globules of water or other substances carried 

 up by vapor — experiments undertaken in consequence of the invention of Arm- 

 strong's machine. Lastly, there are others which only contain the more or less 

 indirect con'Sequences of the fundamental discoveries, which will be explained 

 in one of the three subdivisions under which we have grouped them. We shall 

 not dwell upon an}' of these, thinking that we may give a more exact and com- 

 plete idea of all the progress which Faraday caused the science of electricity 

 and magnetism to make by confining ourselves to pointing out in some detail 

 the most prominent parts of his researches upon these subjects. 



Faraday commenced with chemistry in his scientific career; it is therefore not 

 surprising that he approached eknitricity by the study of electro-chemistry. It 

 was, moreover, towards electro-chemistry that his attention must have been first 

 directed in that laboratory of the Royal Institution which had witnessed the 

 magnificent discoveries of Davy in chemical decompositions effected by the pile, 

 and especially in the production of the alkaline metals. In taking up this sub- 

 ject Faraday only followed the traditions left to him by his predecessor. 



His researches upon the electrical conductibility of bodies constitute a first 

 step in this path. The business was to ascertain whether, as was previously 

 supposed, the presence of water is necessary to render solid bodies conductors, 

 and whether solid non-metallic (and consequently compound) bodies can conduct 

 electricit}' without being decomposed. Commencing with water, which is an 

 insulator when solid and a good conductor in the liquid state, Faraday shows 

 that a great number of compound substances are in the same case. Such are 

 njany oxides, some chlorides and iodides, and a multitude of salts, which do not 

 conduct electricity in the solid state, but, without any intermixtm'e of. water, 



