Uj)on Caloric as a Cause of Galvanic Currents. 273 



These results, satisfactorily prove, that the metals are capable of 

 assuming either state of electricity, according to the direction which 

 the caloric takes, and it will be seen that the effect of association be- 

 tween dissimilar metals, is dependent upon these elementary forces. 

 The order, above given, can be accurately represented only by a 

 measurement of the deviations from the magnetic meridian, as indi- 

 cated by the galvanometer needle ; this, however, I have not been 

 able, hitherto, to execute with the requisite degree of precision, and 

 all, therefore, that is here aimed at, is the representation of the gene- 

 ral electrical states of the different metals, under the same conditions 

 of heat. 



It is obvious, although there are exceptions which will be noticed 

 presently, that the electricity, thus generated by caloric, corres- 

 ponds with the chemical habitudes of some of the metals. Thus an 

 increase of heat makes lead, zinc, iron, he. transmit a negative cur- 

 rent, and these metals may, therefore be regarded as becoming more 

 positive by the operation, the result of which is an increased affinity 

 for electro-negative elements, such as oxygen, so as to render them 

 not only easy of oxidation, but difficult of reduction, when exposed 

 to mere heat : whereas platinum and silver by becoming more nega- 

 tive, at high temperatures, must exhibit a facility of reduction, and 

 other properties the opposite of the former metals. Modifications of 

 this law, arising from volatility, fusibility, he. must always occur, but 

 still the conclusion will be an important one, if it can be shown, by 

 any experimental process, that bodies possess a susceptibility for both 

 electrical states, depending upon the amount of free caloric within 

 them, and not wholly upon the contact of dissimilar matter. 



The galvanometer, however, indicates formidable exceptions to 

 this rule, which must not be passed over. Antimony, for instance, 

 stands first among those metals whose particles, by an increase of 

 heat, transmit a positive current, and it may, therefore, be regarded 

 as becoming more negative by the process. — ^Yet antimony is easily 

 oxidated when heated. The volatility of this metal will, in a great 

 degree account for this result, since it becomes covered with crystals 

 of the oxide at a temperature much below that necessary to make 

 it obscurely red hot ; but the well known attraction which cold anti- 

 mony, in powder, has for chlorine, another electro-negative element, 

 does not admit of so favorable an adjustment. 



The position of gold, moreover, does not indicate its chemical 

 habitude, since it occurs among the metals which are made positive 



Vol. XXV.— No. 2. 35 



