270 Upon Caloric as a Cause of Galvanic Currents. 



can produce similar currents by the contact of metals, unequally- 

 heated. But we must not overlook the marked peculiarities of each 

 mode. Chemistry would be a science of combustion, but for the 

 fluids that are employed in our experiments ; acids would ignite the 

 metals when they oxidate them, just as chlorine is now known to do, 

 could we furnish condensed oxygen, and dispense with water. By 

 the peculiar construction of the galvanic battery, the oxygen is pre- 

 sented in this state, and the oxydizable metal always acquires an ele- 

 vation of temperature so considerable, that, according to M. Parrot, 

 the crust of oxide formed upon i;s surface, at each instant, is red hot. 

 (Ann. de Chimie, 1829.) — But a far more important difference may 

 be pointed out. In the thermo-electric combination, the metals are 

 in actual contact at the very point where the galvanic currents origi- 

 nate, by the application of heat, and this must undoubtedly prove a 

 point of annihilation for much of the electricity, generated. In the 

 galvanic battery, on the contrary, an imperfect conductor is interposed 

 between the metals which generate the currents, so that the latter 

 are compelled to seek an union through the conducting wires. If, 

 however, we make the metals touch, under the acid or saline bath, 

 the result is more like that of the close thermo-electric combination, 

 for the galvanic currents, instead of coursing through the circuit 

 wires, as usual, actually exhaust each other by combination at the 

 point of contact, so as to exhibit litde or no signs of existence outside 

 of the solution. 



It is not, however, my object to discuss the merits of this question, 

 nor do I desire to be considered as having very settled opinions upon 

 a subject still so very conjectural. The enquiry, of which I shall 

 proceed now, to furnish details, originated from an impression that 

 caloric was a very general agent of galvanism, and it was conducted 

 to the termination at a period, when, from the effects of a most seri- 

 ous accident, I was compelled to confine myself to my bed. The 

 leisure which thus presented itself for several weeks, though not un- 

 accompanied by pain, enabled me to arrive at some results which 

 are here offered, solely because they appear to have escaped the no- 

 tice of other chemists, and not with any confident expectation that 

 they can fill up the hiatus which now exists, or lay the foundation for 

 any new theory. 



Notwithstanding the very obvious relations between common and 

 voltaic electricity, it appears highly probable that the practice, which 

 has hitherto prevailed, of employing a common language and similar 



