Metallic Bodies by Voltaic Electricity. 211 



tributable to some peculiar condition of the fine wire employed 

 in the electrometer, by which it is rendered incapable of trans- 

 mitting all the increased power ; and it may be likewise observed, 

 in comparing the above (Table III.) with the previous results 

 (Table II.), that, when the action was comparatively feeble, then 

 the fine wire (Table III.) was the most heated ; but when the 

 action became more considerable, then the larger wire (Table II.) 

 was the most heated. 



8. I repeated these experiments in various ways, and found 

 the results very general and invariable. Thus, in employing 

 three separate electro-magnetic batteries with double copper, 

 each exposing about a square foot of zinc, the effects indicated 

 by the electrometer, with extremely fine wires in the bulb, were 

 nearly as great with one battery as with the three combined, 

 whilst, on the contrary, the indications with larger wires were 

 constantly proportionate to the increased power. 



9. As the diminished effect on the electrometer, when a very 

 fine wire is employed, with an increased charge, evidently de- 

 pends on the imperfect conducting power of the wire, it seems 

 reasonable to infer, that imperfect conducting fluids, such as wa- 

 ter, or extensive quantities of very fine wire, may become almost 

 insulators to this species of electrical accumulation ; and such is 

 found to be the case, since little or no effect is indicated by the 

 instrument, with a given charge, when the circuit xrny, Fig..], 

 consists of an extensive spiral of fine wire, covered with silk ; and 

 no effect whatever, when formed of water contained in glass 

 tubes : hence the accumulation is either insulated, or otherwise 

 transmitted so very imperfectly, as to be quite inappreciable by 

 the heating effect. 



10. The foregoing results are very analogous to those arrived 

 at by Sir HUMPHREY DAVY, in the course of his extensive and 

 justly celebrated inquiries into the laws of voltaic action * ; who 



* Phil. Trans, for the year 1821, p. 435. 



