developed between Metals arid /used Salts. 43T 



binations, they appeared, when fully developed, to have a 

 somewhat superior tension to the currents produced by a 

 couple of platina and silver plates immersed in dilute sul- 

 phuric or nitric acid. If the nitric acid was so strong as to 

 dissolve rapidly the silver, then the voltaic current became su- 

 perior. 



The effect of substituting other metals for one or both of 

 the platina wires still remained to be examined ; but here con- 

 siderable difficulties often arose, from the fusibility and ten-^ 

 dency to oxidation of many of the metals. 



When the platina wires were replaced by wires of palladium, 

 currents in every respect similar were obtained. 



When platina was opposed to palladium, gold or silver, 

 fused soda or borax being interposed, the current was always 

 from the platina through the fused salt to the other metal, 

 provided the platina was at a higher temperature. When the 

 palladium was hotter than the platina, the current was re- 

 versed, or from the palladium to the platina. It was difficult 

 to expose the gold or silver wire to a higher temperature than 

 the platina without fusing it, when a globule of soda or borax 

 was used; but by substituting a more fusible globule, formed 

 of a mixture of the carbonates of soda and potash, the current 

 was readily obtained from the silver or gold to the platina, so 

 long as the former metals were maintained at a higher tem- 

 perature. 



These experiments prove that the position of the metals in 

 the thermo-electric scale does not exercise any influence upon 

 the direction of the current, which is altogether determined 

 by the relative temperatures of the wires. 



When platina at a higher temperature was opposed to 

 copper, fused borax or soda being interposed, the current in 

 very numerous trials (with one or two rare exceptions) was 

 from the platina through the salt to the copper. It was only 

 when from the action of the flame a very rapid formation and 

 solution of the oxide of copper occurred, that the reverse cur- 

 rent was obtained ; but when the chemical action was not con- 

 siderable the current was always from the platina. A current 

 was also obtained in the same direction with boracic acid in- 

 stead of borax. These results are the more interesting, as 

 they prove most distinctly that chemical action cannot be the 

 source of these currents, since in this example the platina 

 would require to have been the metal attacked. 



On substituting iron for copper a violent chemical action 

 took place, the borax or soda became dark and opake from 

 dissolving the oxide of iron, and the direction of the current 

 was in general from the iron to the plalina, even when the 



