On the Excitement of Voltaic Plates. 26 1 



sumptions, however ingeniously they may have been conceived, 

 or however comprehensive may be their grasp. 



Sir Isaac Newton pubHshed his demonstrations of the universal 

 influence of the law of gravitation, in his admirable work De 

 Principiis; his speculatiovs concerning an authorial fluid are 

 thrown together in the form of query at the end of his Optics : 

 but the valuable experiments and discoveries of some philoso- 

 phers are so blended with hypothetical reasoning, that it is dif- 

 ficult to separate the one from the other; and this may in some 

 way account for their having remained without that degree of 

 attention to which their intrinsic worth entitles them, " meiitis 

 noil respondere favorem." 



From the preceding remarks it would no doubt be easy to 

 collect the reasons which prevented my making a reference to 

 those papers on electricity, which had been published by Mr. 

 De Luc previously to the period at which I wrote ; but lest any 

 mistake should arise, allow me to state them explicitly. 



In the first place, I did not conceive that Mr. De Luc had re- 

 futed Sir H. Davy's hvpothesis respecting the cause of chemical 

 affinity, although I did not think it re(iuisite to give at that time 

 the reasons for such an opinion, which being now called upon I 

 have freely explained. 



In the second place, I did not perceive the absolute necessity 

 of insisting that Mr.De Luc's experiments with the Voltaic pliites 

 were from some circumstance coarsely executed. I described 

 my own experiments, and the results; the apparatus employed, 

 and the cautions requisite to be observed ; and I was induced to 

 hope that Mr. De Luc and other gentlemen would repeat these 

 expenments, and that their observations v.'ouUl confirm mine. 



In the third place, In stating some opinions relative to the 

 excitement of the Galvanic pile, I did not notice that they were 

 in opposition to Mr. De Luc's conclusions, because I felt per- 

 ^uaded that all those gentlemen who might honour my commu- 

 nications with a patient perusal, would also be well acquainted 

 with the papers of so distinguished a philosopher as Mr, De Luc; 

 and to their judgement I submitted the difference between our 

 views on the subject, which difference it would be altogether 

 impossible for them to overlook. 



In the fourth place, I did not notice Mr. De Luc's experiment 

 in which a very slight degree of excitement was perceived in con- 

 sequence of friction between a gla^s rubber and glass cylinder, 

 because I did not think it satisfactory in itself; and deeming it 

 at all events an anomalous exception to a general rule, and not 

 likely to be admitted in opposition to strong analogy, I left it, 

 as 1 must now do, to operate with all the force it possesses. 



Having endeavoured, sir, to explain and defend, in a candid 

 K 3 manner. 



