fluid conductors when transmitting the electric current. 183 
tance from the positive pole was still sensible : when, how- 
ever, the zinc formed only a millionth part, no difference 
could be perceived between the alloy and pure mercury. 
35. Lead. An alloy of 200 parts of mercury and 1 of lead 
possessed the positive property in perfection. When the 
proportion of mercury was 667 to 1, the rotation was still 
produced, but was not full and regular. When increased to 
1000, a slight, but sensible current, was perceived to radiate 
from the positive pole to a short distance ; but a proportion 
of 2000 mercury to 1 lead extinguished every trace of 
motion. 
36 . Tin acts also in the same way, and with nearly the same 
energy, as far as I could judge by the eye. It is certainly 
much inferior to zinc. 
37. Iron communicates the property in question, though 
present in such minute quantity as not to be detected by prus- 
siate of potash On the other hand,* Copper does not com- 
municate it, though its proportion be increased to such a 
degree as to give a blue solution in nitric acid, and even to 
render the mercury quite sluggish.* 
38. Of the other metals I have tried, Antimony is the only 
one which appears to exert a perceptible action, and this is so 
slight ( never amounting to more than a mere start, or slight 
convulsion of the surface at the first impression ) that I am 
inclined to attribute it to impurities in the antimony used, 
especially as this metal stands very low in the scale of electro- 
* The amalgam of iron obtained in one experiment was a white friable solid of 
a lustre between silver and iron : the mercury being driven off by heat, the iron 
took fire, and glowed like a live coal till reduced to the state of black oxide, soluble 
in muriatic acid, having all its characters. 
