276 Upon Caloric as a Cause of Galvanic Currents. 



negative current by an accumulation of caloric. This metal, there- 

 fore, like antimony, governs its combinations according to the ele- 

 mentary electricity peculiar to itself, and which always exhibits the 

 positive current moving in opposition to the caloric. 



The other metals are intermediate, in their power, between these 

 two; and, we find one or other of the foregoing laws prevailing ac- 

 cording to the nature of the combinations. 



Arsenic is, most decidedly, a regulating metal, and its influence 

 is in accordance with the elementary condition, as laid down in the 

 table. There it is stated that an increase of heat enables this metal 

 to transmit to the galvanometer a positive current, and when associ- 

 ated, it is found to act most powerfully whenever it is colder than the 

 other metals, previous to contact. Indeed there is little or no effect 

 if the caloric is made to proceed from the arsenic, except in the ca- 

 ses of bismuth, nickel and mercury. In every instance the positive 

 current passes through the arsenic, when the caloric does so, but the 

 polarity is inverted when the hot metal is made to touch cold antimo- 

 ny. There is abundant evidence of a tendency towards the same 

 inversion, when cold platinum, copper, silver, lead, tin, iron or zinc 

 is employed, because, under these circumstances, there is no current 

 rendered manifest, and, accordingly, we may conclude that arsenic, 

 like antimony, governs its combinations, excepting where bismuth, 

 nickel or mercury enters as an element, by the law that caloric and 

 the positive current move together. 



Mercury. The exact relation between unequally heated portions 

 of this metal was not determined, owing to its fluidity, but a suffi- 

 ciently close approximation may be obtained by amalgamating a 

 piece of lead until it becomes able to sustain a drop of mercury — 

 another portion of the fluid metal is then to be heated in a vessel, 

 over a spirit lamp, and after having connected both portions of the 

 mercury with the galvanometer, the suspended drop is to be brought 

 into contact with that which is heated. It will thus be perceived 

 that the portion which receives the caloric, transmits the negative 

 current. In its combinations with other metals, the mercury usual- 

 ly receives caloric, and when by previous heating, it is made to give 

 it out, upon contact, its power is obviously diminished. In two or 

 three cases the polarity even becomes inverted. Thus, cold mer- 

 cury is negative, as to the current, with hot zinc, but positive when 

 the zinc receives the caloric. Tin and silver seem to furnish similar 



