Voltaic BatterieSi 8fC. S7 



might have occurred by having the mass of interposed fluid 

 of variable dimensions was thus avoided. In only one instance 

 was this deviated from, when the plates were removed from the 

 distance of one inch to that of two inches, which alteration, 

 as will presently appear, was too small materially to affect the 

 results of the experiments as they were then conducted. 



11. My first object then is to examine these phaenomena 

 (already determined for one such case) when in connexion 

 with every possible condition as regards the distance of the 

 elementary plates from one another ; or as they are modified 

 by having the mass of interposed fluid of variable dimensions. 



12. Such an inquii'y necessarily includes a repetition of 

 my former experiments, since it becomes requisite to find the 

 area of that plate which at any given distance yields the max- 

 imum effect, as well as to find the effects abstractedly of dif- 

 ferences in the distance, and the influence of acid solutions 

 of different degrees of strength. 



13. Until recently, the magnetic needle has usually been 

 employed to detect and estimate comparative quantities of 

 voltaic electricity evolved by ordinary arrangements. When 

 the results brought out by the preceding inquiry had been 

 satisfactorily ascertained, it was made apparent that between 

 them and others previously determined and admitted as cor- 

 rect, there existed a singular disagreement. It became de- 

 sirable, therefore, to endeavour to reconcile the two methods 

 of observation ; and with this view the experiments which oc- 

 cupy the second part of this paper were undertaken ; having 

 for their object to determine the relation between the deflec- 

 tions of the magnetic needle and the quantity of zinc and 

 other elements expended in producing those deflections; or, 

 in other words (if the principle of observation here employed 

 be correct), to determine the relation between the quantity of 

 electricity and the deflections it produces. 



14. Chemistry has determined the kind of changes which 

 occur among the elements here employed to evolve voltaic 

 electricity; but we know not whether its development be due 

 to the influence of one or more, or all these changes. We 

 have first the resolution of the water into its constituent 

 parts ; the appropriation of the oxygen by the zinc, and the 

 appearance of the hydrogen, as gas, upon the copper; the 

 formation of the oxide of zinc, and, subsequently, of the sul- 

 phate, and the solution of that salt in the water. The present 

 doctrines of chemistry require that these changes should fol- 

 low consecutively, but, as far as we can perceive, they are si- 

 multaneous. 



15. Let some of the attendant phaenomena be examined on 



