xin THE DECOMPOSITION OF THE ALKALIS 



271 



respectively a positive and a negative charge of electricity. 

 This method of producing electric charges was much 

 improved in the VOLTAIC PILE, 1 which he described in the 

 Philosophical Transactions for 1800 (pp. 403-431). This 

 consisted of a series of pairs of zinc (or tin) and silver (or 

 copper) discs, separated by cards, which were soaked in 

 brine to render them conducting (Fig. 43). The voltaic 

 pile had the advantage that the electric charges were 

 replenished as quickly as they were drawn off, so that a 

 continuous ELECTRIC CURRENT could be obtained. The 



FIG. 43. THE VOLTAIC PILE. 



It is composed of 32 discs of copper or silver, A A (e.g. silver coins) and 



32 discs of zinc, z z, separated by cards soaked in brine and terminating in 



two basins of water, b b. 



current was not sufficiently intense to produce sparks, 

 except with the help of a Leyden jar, and would only 

 produce a severe electric shock when the hands were 

 moistened, or, better, dipped into bowls of water, bb \ 

 but even a small pile was capable of producing a far greater 

 quantity of current than the largest of the electrical 

 machines then in use. The power of the pile could be 

 increased almost indefinitely by augmenting the number of 



1 A voltaic pile presented by Volta to Davy is still preserved in the 

 Library of the Royal Institution. 



