Mr. J. Prideaux on the Theory of Voltaic Action, 213 



water, than voltaic by passing through charcoal ; and it seems 

 to follow, that bad conductors act, in case of the shock, by di- 

 minishing its impetus; of the current by reducing its quantity ; 

 and thus allowing of their passing tranquilly through the 

 thermotest wire. 



I think I am prepared to show, on a future occasion, that 

 the heat of electricity is proportionate to, and consequently 

 dependent on, the resistance it encounters in the substance 

 heated ; the shock presenting some analogy with percussion, 

 the current with friction. 



Dr. Hare seems also to have regarded voltaic electricity as 

 acting on particles, and not on masses; an opinion which has 

 of course long yielded to the whole body of facts belonging 

 to electro-magnetism. 



3. Common electricity, produced on non-conductors, is 

 transmitted through a greater or less thickness of air, and 

 must therefore possess a certain degree of tension; by which, 

 when transferred to conductors, it is forced to their surface, 

 and retained there only by the non-conducting power of the 

 surrounding air. 



4. Voltaic electricity is produced through the medium of 

 semi-conductors, and cannot acquire great tension, because 

 the resistance to its return is not sufficient. But by multiply- 

 ing the strata of imperfect conductors through which it must 

 force its way to return ; that is, by increasing the number cf 

 alternations, — this tension may be increased to a limit not yet 

 ascertained. 



Its production is perfectly continuous, and its quantity such, 

 that Van Marum found his great battery charged, by instan- 

 taneous contact with 100 pair of 2-inch plates, as high as the 

 pile itself, — a charge which would have required several turns 

 of his gigantic machine. 



And on this continual flood seem to depend the chemical 

 and (in case of voltaism, where the impetus is small) the calo- 

 rific effect; for weak piles are said by Senger to have their 

 effects remarkably increased, in these respects, by being let 

 offj as it were, over the large conducting surface of a coated 

 jar ; whilst by reducing the magnitude of the plates, confining 

 their points of contact with the liquid (17), or even obstructing 

 the conducting power of the latter, the current may be so re- 

 stricted as to produce tension otily. 



5. Thermo-electricity, being usually produced on perfect 

 conductors, may be expected to be still more free from tension 

 than voltaic electricity; its quantity andcontinuity being marked 

 by its powerful action on the needle. Yet even this may be 

 made to affect the gold leaf electroscope, by using a metal of 



