166 On the Excitement of Voltaic Plates. 



Indies, and until the latter end of last March, not having had 

 an opportunity of obtaining the subsequent nuniliers of his Jour- 

 nal, I was unconscious that what I had written had particularly 

 interested Mr. De Luc. 



I have carefully perused the papers which have been published 

 by him sub5e(]riently to my quitting- Europe, and l-fuve renewed 

 my acquaintance with those which had been previously given to 

 the world. In doing so, I have derived no small degree of plea- 

 sure, and much interesting and important information : but as 

 I suppose the several points of excellence, with whatever defects 

 they may be blended, will be sufficiently obvious to the scientific 

 reader, I have confined the following remarks exclusively to 

 those parts of his writmgs which have been urged against the 

 doctrines contained in my papers ; and I have endeavoured to 

 observe such an order as will put the several points of difference 

 between us in the strongest light. Had I remained in England, 

 the particular train of thought into which I had casually fallen, 

 would probably have led me to further speculations on the sub- 

 ject of electricity; but situate as I am, in an atmosphere ex- 

 tremely unfavourable for electrical experiments, without the 

 means of obtaining philosophical instruments, except after the 

 lapse of several months, from Europe, and with access to very 

 tew philosophical books out of my own circumscribed collection; 

 I have no new matter with which to enrich your Jiages, and it 

 Is with much diffidence I presume to occupy the time of your 

 readers. 



Mr. De Luc considers that he had j;ublished nearly twelve 

 months previously to the appearance of mv Essav on Chemical 

 Affinity*, a refutation of Sir Humphry Davy's hypothesis relative 

 to the principles of chemical affinity, and the decompositions 

 produced by Galvanism. It will be remembered that this hypo- 

 thesis supposed that the elements of all comi)ounds naturally 

 possess different electrical slates or energies, the one component 

 particle being positive, the other negative; that this diiference of 

 electrical state is the immediate cause of chemical union ; but 

 that, when the compound is subjected to a Galvanic battery in a 

 sufficient state of excitation, the particles possessing the negative 

 energy are attracted by the positively, and repelled by the nega- 

 tiveli/ electrified wire; and the particles possessing the positive 

 energy are attracted by the negative/}/ eiectriOed, and repelled 

 by the positivebj electrified wire ; an.d that the force of these at- 

 tractions and repulsions of tlie Galvanic wires to the component 

 particles of a compound body, when greater than the attraction 

 between the component particles arising from the difference of 



■* riiil. Journal, vol. xxix. 



their 



