Upon Caloric as a Cause of Galvanic Currents. 269 



Art. III.— — Upon Caloric, as a Cause of Galvanic Currents; by 

 Prof. John P. Emmet. 



The 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 

 the 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 it 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, even 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 



