438 Prof. Andrews on the Thermo-electric Currents 



latter was at a much higher temperature than the former. 

 However, by fusing a small globule of borax or soda on an 

 iron wire in the reducing part of the flame, and bringing a 

 hot platina wire into contact with it, I obtained a current 

 from the platina to the iron ; but the experiment is difficult 

 to perform and will rareU' succeed. 



When platina was opposed to the following metals, viz. 

 antimony, lead, zinc, and tin, it was with some difficulty that 

 even a mixture of the alkaline carbonates was maintained in 

 a state of complete fusion, the platina being at a red heat, 

 while the other metal was itself almost at the point of melt- 

 ing: the current was in every case from the platina through 

 the fused salt to the other metal. In these cases it was evi- 

 dently impossible to reverse the temperature of the metals. 

 When the interposed globule consisted of chlorate of potash, 

 the current was always from the oxidable metal to the platina, 

 but here the chemical action was very considerable. In the 

 case of the noble metals, the direction of the current was the 

 same with the chlorate of potash as with the other fused 

 salts. 



It appears from the preceding experiments, that an elec- 

 trical current is always produced when a fused salt capable of 

 conducting electricity is brought into contact with two metals 

 at different temperatures; and that when chemical action does 

 not interfere, the direction of the current is not influenced by 

 the nature of the salt or metal, being always from the hotter 

 metal through the fused salt to the colder metal. "J'his cur- 

 rent has an intensity inferior to tliat of the hydro-electric cur- 

 rent developed by platina and zinc plates, but greatly superior 

 to that of the common thermo-electric currents, and is capable 

 of decomposing with great facility water and other electro- 

 lytes. The source of this current may probably be simply 

 referred to the contact between the heated metal and fused 

 salt, which appears to be capable of generating an electrical 

 current, more intense as the temperature of the point of con- 

 tact is more elevated. According to this view, opposite cur- 

 rents are developed at the point of contact of each metal with 

 the fused salts; but that which is produced at the point whose 

 temperature is higher, having a superior intensity, overcomes 

 the other, and its effects alone are exhibited ; just as happens 

 when two similar metallic junctions in a closed metallic circuit 

 are exposed to unequal temperatures. The superior intensity of 

 this current to those obtained from the metals alone, depends 

 probably on the greater obstacle presented to the reunion of 

 the two electricities, at the junctions where they are separated, 

 from the inferior conducting power of the fused salt. 



