216 Dr. Hare oti the Difference bct-J.^een 



intensity as may be effected by the elementary battery of Wol- 

 laston, formed of a silver thimble, and piece of zinc propor- 

 tionably minute. 



It appears from the experiments of Professors W. B. and 

 H. D. Rogers *, that the power of a galvanic pair in deflecting 

 a magnetic needle, was increased by causing the surface of the 

 copper plate to exceed that of the zinc ; while by extending the 

 zinc surface beyond that of the copper, little or no increase of 

 power ensued. This result appears to be the opposite of that 

 which the theory of Wollaston, supported by some recent ob- 

 servations of Faraday, would lead us to expect. As pursuant 

 to that theory, the galvano-electric fluid is due exclusively to 

 chemical reaction ; if the charge were not promoted by an ex- 

 cess of extension in the oxidizable metal, it ought not to liave 

 been improved by similar extension of that which is insuscep- 

 tible of oxidizement. 



According to the observations of the Professors above men- 

 tioned, the deflection resulting from a galvanic discharge, on 

 the first immersion of the plates, after a repose of two hours, 

 was six times as great as that which could be permanently sus- 

 tained. The greatest effect appeared always to ensue before 

 there was any sensible extrication of hydrogen, and the com- 

 mencement of the effervescence was invariably the signal for a 

 decline of power. 



It was by analogous observations respecting the igniting in- 

 fluence of galvanic apparatus that I was led to the construction 

 of my deflagratorst, in which the deflagrating power appears, 

 agreeably to my experience, to be exalted as much by the re- 

 pose of the surfaces as the ability to influence the magnetic 

 needle was ascertained to be, in the experiments of my saga- 

 cious friends above mentioned. 



That the evolution of the galvanic fluid is not in proportion 

 to the intensity of the chemical reaction, is corroborated by the 

 fact, that the intensity of the ignition, excited in a wire by a 

 galvanic discharge, diminishes, while the effervescence in- 

 creases; and it is well known that the power of galvanic ap- 

 paratus is not augmented by adding to the strength of the sol- 

 vent, beyond a very moderate limit. 



But if it be granted that chemical affinity, when reacting 

 within a galvanic circuit, without any propulsive power from 

 the elements of the circuit, can receive a peculiar impulse, so 

 as to produce a current of the electric fluid, confining it at the 

 same time to a very narrow channel, by what process can this 

 species of chemical reaction be conceived to accelerate an elec- 



• See Silliman's Journal for October, 1834. 



t [See Phil. Mag., First Series, vol. Ivii, p. 28 1, lix. p. 1 13. & Ixiii. p. 241 . 

 — Edit.] 



