and on the Construction of Voltaic Batteries. 75 



72 grs. And when the solid mass was extended in its sur- 

 face, or (which is the same thing) when two pounds' weight 

 of sheet copper was joined with the same zinc plate, the 

 amount of action upon it was found to be increased from 7*2 

 to 16*5 grains; the former loss resulting from the influence 

 of a surface equal to ] 6 square inches, and the latter from 

 that of about 170 square inches; showing distinctly that it is 

 to extended surface only that this effect is to be ascribed, and 

 that it is in no respect due to the influence of the better con- 

 ducting power of the metal as a mass. 



It is remarkable that in this law of action to which the fore- 

 going experiments have led me, but which is widely different 

 from any I had anticipated, we have an exact correspondence 

 with the specific gravities of the two gases involved in its ope- 

 ration. The specific gravities of oxygen and hydrogen are as 

 lb' to 1 ; and it is when this proportion between the two sur- 

 faces, upon which they respectively appear, is preserved, that 

 any voltaic combination seems to be placed in the best posi- 

 tion for the exercise of its full power. This correspondence 

 may therefore be presumed to be something more than a 

 mere coincidence. 



Two other points, bearing more immediately upon the ap- 

 plication of these principles to the construction of the batter}', 

 remain to be decided. In the preceding experiments the cop- 

 per plate did not extend over, nor was it placed opposite to, 

 both surfaces of the generating zinc, as in the arrangement 

 adopted by Wollaston; but was placed opposite one face only 

 of it. It therefore occurs, as a part of the inquiry, whether 

 the action upon the zinc took place upon or belonged to that 

 surface only which was next to the conducting copper one, or 

 whether it was due to an influence extending over the whole 

 surface of the zinc immersed : whether, if another copper plate, 

 of the determined dimensions, were placed over against the 

 other surface of the zinc, we should gain a further and double 

 accession of power ? 



Experiment. 1st. A zinc plate, with copper equal to 16, 

 placed on one side only, lost 12*0 grains. 2nd. The same, 

 with two copper plates, one on each side, and presenting, in 

 full, a surface comparatively of 32*, lost 12*3 grains in an 

 equal time. 



There is, therefore, nothing to be gained by apportioning 

 both surfaces of the generating plate, provided the copper plate 

 on the one side be in the full proportion. 



Again : Is the influence of the copper plate due to the exer- 

 cise of one, or of both its surfaces ? Do they both operate or 

 only that one opposite the zinc ? 



L2 



