1/0 On the Excitement nj Voltaic Plates. 



but a very considerable divergence of the gold-leaves. What 

 must be the impression on the mind of your readers from this 

 discordance of statement ? Either that Mr, De Luc's and 

 M. Haijy's experiments were very coarsely performed, or that I 

 have grorisly exaggerated the result of mine. Of the accuracy of 

 my own experiments I cannot doubt, and it is in the power of 

 any gentleman at a trifling expezise to rqjeat them, and decide 

 for himsell". But, sir, you must be aware that I am not the only 

 person who has obtained such results. I can at this t\me par- 

 ticularly refer to M. Volta for support. A description of his ap- 

 paratus, manner of experimenting, and the result of his experi- 

 ments, are contained in tlie following quotation : " Ces plaques 

 ont trois ponces de diam^etre: les metaux doivent etre tres-polis, 

 bien deponilles d'humidite, et apphqueG I'un sur I'autre de ma- 

 niere a manifcster luie cohesion sensible. L"un d'eux doit etre 

 isole, et I'autre doit comnmniquer avec le sol. On doit les se- 

 parer d'un seul trait et perpendiculairement: on fait toucher 

 ainsi celui qui a ete detache au chapeau d'un electrometre, et 

 Oil doit quelquefois un ^cartement des fils*." Volta's plates 

 wore three inches in diameter, mine five ; and as the areas of 

 circles to each other are as the squares of their diameters, it will 

 be seen that my plates were nearly three times as targe as M. 

 Volta's : hence one sufficient reason why the results in my ex- 

 periments were so much more evident than in his; — another 

 reason is however to be found in the extreme delicacy of my 

 electrometer f. But how comes it that in Mr. De Luc's experi- 

 ments it required tu'entij contacts and separations to produce 

 the effect obtained by M, Volta by ojte contact and separation, 

 although the plates of these philosophers seem to have been very 

 nearlv of the same size ? But, what is more extraordinary, how 

 comes it that ten contacts and separations of ^L Haiiy's plates, 

 nearly three times as large as M. Volta's^ were required to pro- 



* Hist, du Galvunisine par Sue, toin. i. p. 254. 



t 'J'his electroraeter cojisists of a glass tube about 4^ inclies long, its in- 

 teriii'.l fliameier a little more than an inch, cappeil witii metal at each ex- 

 treniity. B) one cap it is fixed to its pedestal; in the other cap there is a 

 lioie throngh v. hich a small i;lass tube, an inch and halflonff, passes, and is 

 fastened so that one half is within the body of the electrometer, the other 

 without. The externa! and internal surface of this tube is coated with in- 

 suiating varnish, and throuoh the tube passes a wire, to one end of which 

 may be adapted plates of any size: to the other is fixed a small pair of 

 forceps which receive the gold-leaves. These are IJ inch long and very 

 narrow; their extremities are a full inch fiom the pedestal, and a little more 

 than half an inch from the tinfoil. — Now the circumstance which, indepen- 

 fifnt of the size of the instrument, contributes to make it more delicate 

 than electrometers of this kind generally are, is the gold-leaves being con- 

 ncctetl with nothiug but the wire — not with the cap, as is generally the 

 case. 



duce 



