346 GALVANISM. 



was not only the source of the electricity of the pile, but also of the common 

 electrical machine. He showed that by conveying the electricity of the ma- 

 chine to gold wires terminated in extremely fine points the decomposition of 

 water could be effected, and that the phenomenon was the same as when the 

 decomposition was effected by Voltaic wires. He maintained that the friction 

 of the rubber was attended with oxydation, and showed that the machine waj 

 ineffective in an atmosphere of dry hydrogen, or any ether gas in which chem- 

 ical action was not produced. 



If an oblono; slip of wet paper have its extremities in contact with the poles 

 of a Voltaic pile, each half of the slip will be electrified ; that which is in con- 

 tact with the positive pole will be positively electrified, and that which is in 

 contact with the negative pole will be negatively electrified. If it be removed 

 from contact with the pile by a rod of glass, or other non-conductor, its electric 

 state will continue. This means of producing electrical polarity was observed 

 by Volta, and about the same time by Erhman. 



This fact suggested to Ritter the idea of his secondary pile, which consisted 

 of a series of disks of a single metal alternated with cloth or card, moistenea 

 in a liquid by which the metal would not be affected chemically. If such &, 

 pile have its extremities put in connexion by conducting substances with tht 

 poles of an insulated Voltaic pile, it will receive a charge of electricity in u 

 manner similar to the band of wet paper, one half taking a positive and tht, 

 other a negative charge ; and after its connexion with the primary pile hd*. 

 been broken, it will retain the charge it has thus received. The secondary 

 pile, while it retains its charge, produces the same physiological and cheftnica* 

 effects as the Voltaic apparatus. 



The polarity which the band of wet paper and the secondary pile acquit 

 by their temporary contact with the ends of a Voltaic apparatus, is a coiibe 

 quence of their imperfect conducting power. The electricity of each specie* 

 appears to force its way through the imperfect conductor till the two opposite 

 currents meet in the centre. 



At the time of the discovery of the secondary piles, it was known that a piect- 

 of metallic wire, the ends of which had been placed in contact with the poles 

 of a Voltaic pile, does not instantly recover its natural state when its contact 

 with the pile is broken. 



From the experiments of Davy and others, it appeared that if a communica- 

 tion was made between the poles of an insulated pile and two glasses of water, 

 so that the water in the one would be charged with positive, and the other 

 with negative electricity, a metallic wire connecting the two portions of water 

 would evolve oxygen gas at one point, and hydrogen at the other. If, under 

 such circumstances, the connexion of the glasses with the pile be suddenly 

 broken, the action of the wire will nevertheless continue for some time, but its 

 effects will be reversed ; the point which before disengaged hydrogen will 

 now disengage oxygen, and vice versa. It appears, therefore, that, the sudden 

 suspension of the action of the pile has the effect of reversing the direction of 

 the electric current which passes through the wire.* 



The continuance of the electric state of a wire which had been used to con- / 

 nect the poles of a pile after its separation from the pile was also demonstrated \ 

 by Oersted, who showed its effect on the organs of a frog.f The same effect , 

 was produced by a wire through which the current of a powerful electrical 

 machine had been transmitted 



From the chemical effects of the pile, Davy turned his attention to its calor- [ 

 ific powers. The means of experimental investigation placed at his disposal j 



) 



* Histoire de Galvanism de Sue, torn, iii., p. 341. 

 t Journ. de Opim. de Van-Mons, No. iv., p. &8. 



