262 Mr. Prideaux's Experimental Contributions 



voltaic electricity, is evident, for the " usual shocks" only were 

 produced, and nothing like the terrible sensation due to a 

 voltaic battery, even when it has a tension so feeble as not to 

 strike through the eighth of an inch of air. 



34-1. It seems just possible that the air which was passing 

 by the kite and string, being in an electrical state sufficient to 

 produce the " usual shocks" only, could still, when tlie elec- 

 tricity was drawn off below, renew the charge, and so con- 

 tinue the current. The string was 1500 feet long, and con- 

 tained two double threads. But when the enormous quantity 

 which must have been thus collected is considered (371. 376.), 

 the explanation seems very doubtful. I charged a voltaic 

 battery of twenty pairs of plates four inches square and with 

 double coppers, very strongly, insulated it, connected its posi- 

 tive extremity with the discharging train (292.), and its nega- 

 tive pole with an apparatus like that of Mr. Barry, communi- 

 cating by a wire inserted three inches into the wet soil of the 

 ground. This battery thus arranged produced feeble decom- 

 posing effects, as nearly as I could judge answering the de- 

 scription M. Barry has given. Its intensity was, of course, 

 far lower than the electricity of the kite-string, but the supply 

 of quantity from the discharging train was unlimited. It of 

 course gave no shocks to compare with the " usual shocks" of 

 a kite-string. 



34-2. Mr. Barry's experiment is a very important one to 

 repeat and verify. If confirmed, it will be, as far as I am aware, 

 the first recorded case of true electro-chemical decomposition 

 of water by common electricity, and it will supply a form of 

 electrical current, which, both in quantity and intensity, is 

 exactly intermediate between those of the common electrical 

 machine and the voltaic pile. 



[To be continued.] 



XL VI. Experimental Contributions towards the Theory of 

 Thermo-electricity. By Mr. John Prideaux, Member of 

 the Plymouth Institution. 



[Concluded from p. 215.] 



V. What are the electrical conditions of Homogeneous Metals 

 brought into contact at different temperatures ? 



19. 'TWO copper wires, -J^th of an inch in diameter, had a 

 -*- flat spiral, f in diameter, turned in each, the central 

 end of the wire being drawn out perpendicular to the spiral, to 

 enter a cork, for a handle; the external end being continued 

 in a line, nearly parallel with the face of the spiral, for 8 



