150 EE^ISIOXS OF THE THEORY OF ELECTROLYSIS. 



with wouiler solid aud fluid substances assuming uew modes of existence in 

 different gases. Do not the new phenomena of galvanism authorize us to 

 hope that at no very distant time they will behold even those gases undergoing 

 novel changes and existing in new aud now unknown forms? 



The diffuseness and lack of conereteness of ideas in those early 

 days of the science, before the time of Ohm's law, are strikingly 

 illustrated in the following extract from a syllabus of a course of 

 lectures delivered by Davj^ in the theater of the Royal Institution 

 in January, 180:2 : 



The agency of the galvanic influence which occasions chemical changes in 

 water and communicates shocks to the living body is probably in some measure 

 distinct from that agency which produces sparks aud the combustion of bodies. 

 The one appears, all other circumstances being similar, to have little relation 

 to surface in compound circles, but to be great in some unknown proportion as 

 the series are numerous. The intensity of the other seems to be as much 

 connected with the extension of the surface of the series as with their number, 



Davy was not at that time able to distinguish between electro- 

 motive force or electric pressure and strength of current. 



The long contest waged between the supporters of the contact 

 theory of electric action in a voltaic couple and the chemical theory 

 is briefly alluded to in this same syllabus, without any clear intima- 

 tion of the position taken by Sir Humphry himself : 



M. Yolta has supposed that an electrical current is always produced by the 

 mere contact of certain different conductors of electricity. But many of the 

 British philosophers have denied this position, accounting for galvanism from 

 the destruction of the equilibrium of electricity in galvanic circles in conse- 

 quence of the chemical agencies of the different bodies composing them. 



On Xovember 20, 1806, Davy read before the Royal Society a 

 Bakerian lecture on '" Some chemical agencies of electricity,"" In 

 this lecture he takes a decided position against the chemical theory 

 of electrical excitation held by many British philosophers. He says : 



The general ideas advanced in the preceding pages are evidently directly in 

 contradiction to the opinion advanced by Fabroni, and which, in the early 

 stages of investigation, appeared extremely probable, namely, that chemical 

 changes are the priDianj causes of the phenomena of galvanism. 



Before the experiments of M. Yolta on the electricity excited by the mere 

 contact of metals were published, I had to a certain extent adopted this 

 opinion ; but the new facts immediately proved that another power must 

 necessarily be concerned. 



In this same lecture we find suggestions by this distinguished phil- 

 osopher harmonizing with the celebrated theory of Grotthus; but no 

 credit is due to Dav}- for these suggestions, because Grotthus pub- 

 lished his theory in the year 1805 in Rome under the title : " Memoire 

 sur la decomposition de Teau et des corps, qu'elle tiont en dissolu- 

 tion, a Taide, de I'electricite galvanique." A second edition followed 



