on Voltaic Combinations and Arrangements. 291 



evolved from ihe surface of the platina. The only point 

 worthy of remark is, that the oxidated or dissolved zinc re- 

 mains entirely, or by far the greater portioi), on its own side 

 of the diaphragm : this is an argument for the secondary na- 

 ture of metallic precipitation by voltaic electricity. And yet 

 this theory of reduction by the nascent hydrogen supposes 

 first, that oxygen quits hydrogen to unite with zinc, and then 

 that it quits zinc to unite with hydrogen : this reversal of af- 

 finities is a stumbling-block difficult to surmount. Mr. 

 Daniell has in his last paper given some additional argu- 

 ments in favour of immediate precipitation : for the present 

 I feel incompetent to pronounce any other opinion upon the 

 subject but that of Sir Roger de Coverley. 



As it seems probable that at no very distant period voltaic 

 electricity may become a useful means of locomotion, the ar- 

 rangement of batteries so as to produce the greatest power 

 in the smallest space, becomes important. I have turned this 

 matter in my mind from reading the letter of Prof. Jacobi, 

 published in the last Number of the Phil. Magazine, and of 

 course I could not avoid measuring the results of my battery 

 with those to which he alludes ; my data, however, for such 

 comparison are very imperfect. Prof. Jacobi says, " at pre- 

 sent (June 21st) a battery with a decomposing apparatus 

 which will produce from 3 to 4 cubic feet of electrolyzed gas 

 per hour occupies little more space than the page on which 



I write (stated, I presume by Dr. Faraday, to be 10 by 8 

 inches) and is about 9 inches high." Now, allowing " the 

 little more space " for the decomposing apparatus, and sup- 

 posing expense no consideration, I should, as the most con- 

 venient way of utilizing the metals, construct four vessels of 

 platina 2^ inches by 9 and 8, each separated from the other 

 by a thin layer of glass and divided internally by two parti- 

 tions of platina. We should thus have 1 2 cells ^ of an inch 

 wide, into which would fit the flat porous vessels ; and when 

 arranged as a series of four, each pair would expose a sur- 

 face of platinum of 497 square inches. Supposing then, with 

 Gay-Lussac and Thenard, that for a given combination and 

 given series the chemical power is as the surface, we should 

 have 14 : 6 : : 497 : 213 cubic inches per minute, or nearly 



II cubic feet per hour. I know this calculation will seem 

 gigantesque, and nobody can be more convinced than myself 

 that experiment would fall short of it ; still it cannot, I think, 

 be doubted that a very large proportion of this result may 

 be obtained, and by a proper adaptation of funnels and si- 

 phons may be kept up for an indefinite period. There is 

 yet a method which would offer a larger negative surface 

 than this; it is to intersect the diaphragms with others, thus 



U2_ 



