On Galvanism. 171 



T conceive the following propositions will be admitted as 

 axioms in this science : 



1st, The quantity of fluid evolved is proportionate to the 

 quantity of metal oxidated, whether the oxidation of the 

 metal be the mediate or immediate cause of its evolution. 



2d, The quantity of metal oxidated is in proportion to 

 the extent of surface exposed to the action of a proportionate 

 quantitv of acid. Thus four parts of ac'd will produce four 

 times as much oxide from an eight-inch plate, as one part 

 would from a plate of four inches. 



3d, The fluid evolved is, from the equal attraction of 

 equal portions of the conducting body for ecpiul portions of 

 the fluid, diftlised equally over every equal portion of tlie 

 conducting substances of which the battery is composed, 

 in proportion to the conducting powers of each respec- 

 tively. 



4th, The quantity of fluid transmitted through metallic 

 arcs is measured by the degree of ignition produced. 



.5th, The intensity of the shock received is the measure 

 of the quantity of fluid transmitted through animals. 



Hence it will follow, that from a battery of 25 eight-inch 

 plates, or of 100 of four inches, four times as much fluid 

 will be evolved as from one of 25 four-inch plates, sup- 

 posing the distance between the plates equal, and the same 

 proportion of acid employed in both cases ; or, in other 

 words, the fluid evolved \\'\\\ be as the area of all the plates 

 taken together, and it will be equally diffused over the whole 

 surface of each battery in proportion to the conducting power 

 of its several parts. 



Now suppose the skin, from its imperfect conducting 

 power, incapable of transmitting more fluid than is evolved 

 from a battery of 25 four-inch plates, and that this supposi- 

 tion will account for the intensity of the shock not being in- 

 creased when 25 eight-inch plates are used ; so far the hict 

 and theory would agree. But under other circumstances 

 this theory Involves contradiction and absurdity, f'or ex- 

 ample, as no difference in the intensity of the -shock is per- 

 ceived, whether 25 four-inch or 25 eight-inch plates be 

 used, the skin cannot transmit more fluid than is given out 

 by 25 four-inch plates. 



But the skin will transmit from 100 four-inch plates a 

 greater quantity of fluid tlian from 25 plates of the same 

 size ; 



Therefore the greater and lesser quantities are equal : for 



tlu; skin caimot at the same time have, and not have, Ihe 



3 power 



