Upon Caloric as a Cause of Galvanic Currents. 275 
are capable of generating, when placed in contact previous to. the ap- 
plication of heat. In general, very small fragments or wires, and the 
me of a spirit lamp, will furnish satisfactory results; but, in some 
instances, one of the metals must be employed in large masses and 
the requisite temperature obtained by a charcoal fire. 
The disturbance of the ordinary currents, is momentary, or at 
least, lasts only while the difference of temperature continues so 
great as to give the caloric a direction contrary to that which it would 
take when the metals are heated in contact with each other. 
_A few examples will render the nature of these modifications more 
apparent. 
Antimony, when heated in contact with the Gligaias metals, bis- 
muth, nickel, copper, platinum, &c. invariably conveys a positive 
current to the galvanometer; but when made obscurely red-hot, 
previous to the contact, its polarity becomes reversed with every 
metal tried, except bismuth, nickel and mercury, which, being at 
the remote end of the thermo-electric scale, in relation to antimony, 
exhibit only a feeble diminution of force. The conclusion obvious- 
ly to be drawn from this example, is, that antimony, while in contact 
with copper, platinum and most other metals, receives caloric from 
em; because, when, by excess of heat, it is compelled to give it 
out, the ordinary galvanic currents become Teversed. Another re- 
sult is, that in such cases the caloric and we current move in the 
same direction. Upon referring to the electrical condition of its par- 
ticles, when unequally heated, as before stated, it will be seen that an 
increase of heat makes antimony transmit a positive current, so that 
it is obvious, this metal governs the currents proceeding from the 
combinations just noticed, according to its own dlementary condition 
in relation to caloric. - 
_Bismura furnishes examples of the opposite character. Its po- 
arity continues uniform, whether it is heated in contact with the met- 
als, or whether the latter are made hotter or colder, previous to the 
contact. But, in most cases, its power of transmitting a negative 
current is diminished when the caloric is made to proceed from it, 
and, as this diminution is undoubtedly indicative of a tendency to- 
wards inverted polarity, we may infer that in all its thermo-electric 
combinations, it acts by receiving caloric, like antimony—such a con- 
clusion is strengthened by the elementary condition of its own par- 
ticles, which, it has been shown, become capable of transmitting a 
