272 Upon Caloric as a cause of Galvanic Currents. 
originate at the very point of contact. This fact, taken in comec- 
tion with the views advanced by Volta, in order to explain the action 
of his pile, seems to have led persons to suppose that the contact of 
dissimilar metals was necessary, and accordingly, almost all the re- 
sults obtained, upon the subject of thermo-electricity, relate to the 
combination of different metals. Yet it is easy to show, by the gal- 
vanometer, that two portions of the same metal, are capable of act- 
ing upon each other, and that the currents, thus generated, depend 
solely upon the direction which the caloric is made to take. Thus, I 
found, that, when a hot fragment of bismuth, was made to touch a 
cold one, the former constantly transmitted a positive current to the 
galvanometer ; whereas, when fragments of antimony, unequally 
heated, were brought into contact, the hot portion, invariably, con- 
ducted the negative current. ‘These two metals are, therefore op- 
posite to each other, in this respect, and when combined, must from 
the point of contact, send forth the two fluids in opposite directions. 
All the other metals, tried, were capable of producing currents by 
the simple contact of their own particles, unequally heated, but bis- 
muth and antimony possess the greatest power. The currents cease 
almost immediately, upon the contact of particles, obviously, because 
the inequality of temperature, is thus at once destroyed ; whereas, 
when dissimilar metals, are heated in contact with each other, the 
difference of temperature, must still subsist owing to the greater ca- 
pacity for caloric and conducting power of one of the metals. In 
such cases, the direction of the galvanic current, is determined by 
the direction which the excess of caloric takes through the metallic 
medium. Heating one fragment before its contact with the other, 
enabled me, in most cases, to determine the directions which the 
caloric and galvanic currents take, and the results, I think, will show 
that this mode of investigation is of the utmost importance. The 
following tabular view represents, nearly, the order in which the met- 
als stand in relation to their elementary galvanic powers. The caloric, 
it is obvious, must be considered as proceeding from the hot fragments 
to the cold as long as there is any difference of temperature. 
Contact between portions of the same metal unequally heated. 
pos. current in—antimony, arsenic, platinum, copper and 
Increase | silver. (Law—caloric and pos. current move togeth- 
of hea * 
devel 
opes a | "eg. current, in lead, tin zinc, gold, iron, mercury? nickel 
and bismuth. Law—opposition = > 
