1824.] Conductors when transmitting the Electric Current. 273 



20. But the effects did not stop here. On prolonging the 

 contact a considerable time, the negative current (from z) was 

 not only wholly destroyed, but changed into one of a contrary 

 tendency ; i. e. radiating in all directions to z ; the particles of 

 the mercury appearing to be attracted to that point with a force 

 equal, or superior, to that with which they were repelled 

 from f. The positive pole being held at some distance, and the 

 negative directly over the surface, any scum or impurity on the 

 mercury was observed to collect directly under it, in a small 

 circular spot, following exactly its motions ; and when this was 

 cleared away, the fluid metal was violently thrown up towards 

 the wire in a jet of two or three-tenths of an inch in height. 



21. The mercury was now brought into contact with the positive 

 wire. Visible oxidation did not commence on its surface for a 

 long while, during which time violent currents still continued to 

 radiate in all directions from the wire and towards the point z 

 (or in a direction opposite to what they would have taken in 

 untouched mercury). By degrees, however, a counter-radiation, 

 commenced opposite to the negative pole, whose sphere was at 

 first very limited, but gradually extended, producing a zone of 

 equilibrium, which advanced rapidly towards the positive wire, 

 and at length attained it. The instant this took place, the oxi- 

 dation of the mercury commenced at z, and speedily extended 

 over the whole surface, forming a thick crust. 



22. If the contact of the positive pole was continued long 

 enough, the mercury, on cleansing it from its coat, was found 

 reduced to its former state, as if freshly introduced ; but if 

 broken as soon as the crust was fully formed, a radiation from 

 the negative wire was produced, and the crust broken up and 

 swept by it to c, where it collected, and was hurried off'. But 

 the moment this was done, and the surface of the mercury had 

 become bright throughout, it stopped for an instant, and imme- 

 diately a violent revulsion took place, and a powerful current 

 radiated from c, that from z being annihilated. 



23. These effects, when first observed (not connectedly in 

 regular succession, as here set down, but piece-meal), appeared 

 exceedingly perplexing ; but the key to them was soon found. 

 I observed that the effect of a contact of the negative pole was 

 proportionally stronger in producing a positive radiation, as the 

 mercury had been allowed to circulate longer before the contact 

 was made, and, on more close examination, I found that the 

 platina wire terminating the negative conductor of the pile, had 

 got amalgamated with a little mercury, which, during the time 

 the circuit was completed in the liquid, had become alloyed 

 with sodium; and, with the quantity of this metal judged to be 

 present, the effect seemed always to be in proportion. I had 

 no hesitation, therefore, in attributing all the new properties 

 acquired by the mercury to the presence of sodium, and on 



New Series, vol.. vm. T 



