Galvanic Batteries. 139 



times, prove, beyond a question, a fact which rather contravenes 

 our experience in galvanic philosophy. A priori, we should have 

 decided in favor of the wet plate, as the conducting liquid would 

 be brought more immediately into contact with it, by means of 

 the thin stratum of liquid already adhering to the plate. Whether 

 dryness alone be the condition required for this superior action, or 

 some other condition necessarily involved in the absence of mois- 

 ture, I am unprepared to say ; the course of my investigation hav- 

 ing been discontinued at this point. The subject is worthy of a 

 thorough examination, and seems to promise some new and import- 

 ant developments in respect to the construction of the galvanic 

 battery. The introduction of metallic salts as galvanic motors, and 

 of membranous partitions to prevent the degeneration of action, 

 have much improved the battery as an instrument for research. 

 But it must be confessed that the batteries with the membranous 

 linings, are very inconvenient, and require too much attention 

 from the vitiation and decay of the membrane. The gain, too, 

 is so trivial over the unprotected batteries where sulphate of cop- 

 per is used, that I have always preferred, for ordinary use, the 

 revolving zinc plate battery, described in a previous number of 

 this Journal,* or else the cylindrical, or square plate battery, 

 where the zinc plate is movable and supported entirely indepen- 

 dent of the copper. The revolving zinc plate battery gains the 

 benefit of fresh immersion by the withdrawal, cleaning, and dry- 

 ing of the zinc plate without a cessation of action. But the gain 

 by fresh immersion is by no means so great here as in the pre- 

 sentation of a dry copper plate in the amalgam battery. It fre- 

 quently happens that a battery does not act until some minutes 

 after its immersion. In the acid battery the failure is owing to 

 the foulness of the zinc plate, which must be removed or pene- 

 trated by the acid before it can act upon the zinc. In the sul- 

 phate of copper batteries, the failure of action may arise from 

 the foulness of either plate. Hence it is important to observe, 

 that both plates should be thoroughly cleaned when they are to 

 be used with the sulphate of copper. If the zinc plate be per- 

 fectly cleaned, there will be scarcely any galvanic action if the 

 copper plate is immersed, as it not unfrequently is, covered with 

 a film of insoluble carbonate. In the revolving plate battery no 



* See Vol. XXXII, p. 359. 



