Upon Caloric as a Cause of Galvanic Currents. 269 
Arr. III.—Upon — as a Cause of Galvanic nets by 
Prof. Joun P. Emmet. 
Tue subject, for the illustration of which the following inquiry was 
instituted, is one of undiminished interest to the philosopher, who, 
notwithstanding the able controversies hitherto maintained between 
e champions of simple contact on the one hand, and those of chem- 
ical action, upon the other, must still feel abundantly convinced that 
the theory of galvanic action is yet but imperfectly understood. 
Scarcely has opinion settled down, ere a new view of the question, 
brought to light by Faraday, and matured by Nobili, Antinori and 
others, rises up to convince us that this same galvanism can exist in- 
dependently of either caloric or chemical action; and we are com- 
pelled to admit, that, however important these causes may be, -mag~ 
netism is fully as much so. 
Indeed, if we look to the matter closely, there is reason for believ- 
ing that magnetism is the most elementary agent, since tt is always 
present, whereas the others are not. ‘Thus, when galvanism is pro- 
duced by the contact of acid and dissimilar metals, or by that of the 
latter alone, under the influence of heat, magnetism appears in every 
portion of the apparatus, and no method has hitherto been devised for 
determining which precedes the other. Magnetism, in these cases, 
may, therefore, be the cause of the galvanic currents, instead of the 
effect ; whereas, in the experiments with the horse-shoe magnet, 
there is no reason for believing that either caloric or chemical action 
is, evén in the most indirect manner, connected with the results, but 
on the contrary, that the only cause is magnetism. 
Applying the same reasoning, we are led to conclude that caloric 
is a more general agent than chemical action; since the former is 
set free in every case of galvanic excitation, depending either upon 
salts, acids, or inequality of temperature ; whereas there is no influ- 
ence from chemical action, as Becquerel has proved, when two 
metals are brought into contact and heated. Under such circum- 
stances, we might almost feel justified in concluding, that whenever 
chemical action seems to be necessary for the effect, its true agency 
consists in putting caloric or magnetism into motion. The great en- 
ergy of the common galvanic battery may be urged as an objection 
to this opinion, that caloric is the general cause of galvanic currents; 
since we find that a very high temperature is necessary before we 
