186 Mr . Herschel on certain motions produced in 
40. 1 was anxious to examine whether similar motions would 
be produced in other metals than mercury and its alloys, when 
in fusion. The foregoing experiments, indeed, leave little 
room to doubt their capability to do so ; but the nature of the 
case throws great difficulties in the way of direct experiment. 
I have been successful hitherto only in the case of the fusible 
alloy of lead, tin, and bismuth, no mercury being present. 
This, with a little management, may be preserved tolerably 
clean of film and air bubbles, when kept in fusion under a 
boiling solution of sugar, acidulated with phosphoric acid, in 
which case the same circulation takes place as in the case of 
mercury, viz. from the negative to the positive pole. When 
solution of sugar alone however was used, the influence of the 
tin and lead became sensible, the predominant radiation being 
from the positive pole ; a feeble counter- current being, how- 
ever, observed from the negative. 
41 , The contact of the positive pole, in like manner, com- 
municates peculiar properties to mercury, but less strongly 
marked, and which appear to depend, in part, on the film of 
oxide formed on its surface, and partly on an absorption of 
oxygen by the metal itself ; a thing rendered not improbable 
by the analogy of silver and other metals, which when fused 
in contact with air, absorb oxygen without losing their me- 
tallic appearance. The facts I have observed are chiefly 
these : 
42. Equal quantities of mercury were electrified for equal 
times in two separate capsules, under similar solutions of 
carbonate of soda, one in contact w 7 ith the negative wire, and 
the other with the positive. On mixing them together, the 
mercury was acted on as if pure, and showed no signs of 
