1820.] Franklin's Theory of Electricity 447 



electric sparks are, in every instance, directed towards the same 

 side ; and he could no longer doubt of the accuracy of the draw- 

 ing which I had shown him of the ray produced by the Teyleriaa 

 machine ; after too he had seen, by means of this appara- 

 tus, that the ramifications proceeding from the positive conductor 

 take a direction towards the opposite one, and evidently indi- 

 cate that the spark is emitted by the opposite conductor ; but, 

 on the contrary, that similar ramifications of the spark at the 

 negative conductor are directed towards the other, and thus 

 indicate the transition of this spark from the opposite conduc- 

 tor towards the negative conductor, I asked him if the then so 

 evident direction of the sparks did not satisfactorily prove to 

 him that, in either instance, they ought to be attributed to the 

 current of a single fluid, which, whenever there is a superabun- 

 dance of electric fluid in the conductor, is emitted from it in 

 order to pass to the neighbouring one, and that this current, on 

 the contrary, when the conductor is deprived of the electric fluid, 

 transmits itself from the conductor adjoining the negative one 

 itself? To this question I added another ; namely, whether, on 

 the contrary, these difterent directions, so clearly indicated by 

 the sparks, could be made to agree with his conjecture, that 

 the electric spark is occasioned by two different fluids ap- 

 proaching each other in opposite directions, and uniting in the 

 spark itself. 



To these questions, he replied that what he had just seen 

 might very well accord with his theory, adding, at the same 

 time, that he was not able at once to give me his ideas on the 

 subject, but judged it more proper to correspond with me 

 upon it in writing ; and that immediately on his return to Paris, 

 he would inform me how what he had seen might be explained 

 conformably to his theory. Yet although this occurred in Au- 

 gust, 1810, I have never yet received the promised answer. 

 Thus I am still unacquainted with his theory of electrical pheno- 

 mena, a work, which, as he informed me, it was his intention to 

 pubUsh shortly after his return to Paris. 



They still continue in France to adhere to the theory of two 

 sorts of electric fluid, as I have at several different times had 

 occasion to observe, among others by Thenard's Traite Elemen- 

 taire de Chimie. Paris, 1813. In this work, M. Thenard, 

 speaking of Volta's electric column as a chemical instrument 

 (torn. i. p. 91) explains the apparatus and its phenomena on the 

 theory of vitreous and resinous electricity, although Volta him- 

 self derives the explanation of his invention entirely from the 

 more simple and better supported theory of Franklin. 



But, it may be asked, have either the French Academicians, 

 or any other learned men, alleged more recently new reasons or 

 experiments which have induced them to return to the old 

 opinion, although that of Franklin was still received by them. 



It is my intention to examine maturely with you whatever has 



