282 Mr. Mulliiis on the Development and Action 



lie, in the belief that the results of a series of experiments, 

 conducted with care and frequently repeated, fully justify me 

 in asserting that every battery in present use, which contains 

 equal surfaces of zinc and copper, is constructed on a wrong 

 principle, and that in such batteries an enormous quantity of 

 zinc is consumed without the slightest advantage. I was first 

 struck by this fact while experimenting with the Wollaston 

 battery, for I always remarked that the zinc plates were un- 

 equally corroded, the action being much greater within an 

 inch of the lower edge of the plates than higher up. I also 

 found that after using these plates for some time, when of 

 course the original extent of surface was much diminished, 

 the power of the battery was quite as great as at first, as- 

 suming that the plates were clean and the battery fresh 

 charged. In consequence of these observations I reduced the 

 size of the zinc plates to a fourth of what they had previously 

 been, and could not perceive the least diminution in effect; 

 so that without any greater action in a given time on that part 

 of the -zinc which I retained, I was enabled to develop the 

 same power, thereby avoiding the waste caused by the action 

 of the solution on the remaining parts of the larger plates. 

 Having thus satisfied myself that a large quantity of zinc ab- 

 solutely went for nothing in the common batteries, I entered 

 upon a new series of experiments on the same subject with 

 my sustaining battery, which, in consequence of its power 

 not diminishing, gave me a certainty of still more accurate and 

 satisfactory results than I could have hoped to obtain from a 

 battery whose power was unequal. In order that others who 

 may be prejudiced in favour of equal metallic surfaces may 

 have an opportunity of convincing themselves of the truth of 

 what has bei-n stated, I think it may be well to give them an 

 account of a few of the experiments made with the sustaining 

 battery, which they may perform without any difficulty. 



One of the tests of which I availed myself was the magnetic 

 voltameter, which, for the measurement of small quantities of 

 electricity or of that of low tension, is, without doubt, as accu- 

 rate an instrument as any we know. In these instruments there 

 is of course this defect, that no two of them will, for the same 

 quantity or force of electricity, afford the same indication in 

 degrees, which arises from difference in the size of the needles, 

 length and number of coils, thickness of the wire, &c. ; but 

 where the same instrument is applied in the comparison of 

 different effects, it is, as I before stated, as perfect as any with 

 which we are acquainted. If then we connect this instru- 

 ment with one of my small cylinder batteries, the copper in 



