Upon Caloric as a Cause of Galvanic Currents. 277 



results, but, the combinations being extremely weak, the effects are 

 difficult of observation. 



The combination between zinc and mercury will enable us to trace 

 tlie relation which the direction of the caloric bears to that of the 

 positive current, for if these metals are heated together, the mercury 

 transmits a negative current. The contrary is shown to be the case 

 when this metal gives out caloric to the zinc, and the inference, there- 

 fore is, that in the usual combination, where contact is first establish- 

 ed, the mercury receives caloric from the zinc, and, accordingly, 

 the caloric and positive current must move in opposition to each oth- 

 er. This result corresponds with the law of its own particles, as giv- 

 en in the table, and is moreover exemplified by the combinations 

 between mercury and the metals, iron, silver, antimony, tin and ar- 

 senic, provided these metals are made hotter than the mercury. 

 The caloric and positive current move together, however, in the 

 combinations of hot mercury and cold iron, cold antimony and cold 

 arsenic. 



The other thermo-electric combinations furnish results which vary 

 for each case ; it will not, therefore, be necessary to explain their 

 peculiarities farther than by the tabular view which follows, and with 

 which I shall close this communication. The relative direction of 

 the caloric and galvanic currents may thus easily be perceived, and 

 by consulting the table already given for the elementary condition of 

 each metal, under the influence of temperature, we may generally 

 arrive at a knowledge of that one which governs the currents. To 

 facilitate the application of the principles indicated in the preceding 

 remarks, I have represented the direction of the caloric by an arrow 

 with a head composed of dots, and feathered at right angles to the 

 shaft. The course of the positive galvanic current is indicated, on 

 the other hand, by an arrow of the usual form. 



