fluid conductors when transmitting the electric current. 187 
containing sodium. Here, the mercury in contact with the 
positive pole had acquired a virtue capable of counteracting 
the effect of a considerable impregnation of sodium, which, 
had it not been counteracted, could not fail to be violent. 
43. When mercury is kept in contact with the positive pole, 
the surface contracts a film of oxide of more or less consi- 
derable thickness. Now, break not only the contact, but the 
circuit. The mercury will be quite still ; but the moment it 
is touched with a clean metallic wire (not electrified), the 
oxide disappears rapidly at the point of contact, as if absorbed, 
and the remainder rushes in on all sides to supply its place, 
producing a system of current in the surface radiating to- 
wards the wire. It is not indifferent with what metal the 
contact is made ; potassium, sodium, barium, tin, and zinc, are 
those which produce the most violent action, the surface 
brightening instantly with a kind of flash like the brandishing 
of melted silver, tin being in this respect superior to zinc. The 
effect of iron is pretty considerable, that of copper less so, and 
of antimony and platina, none at all ; neither had phosphorus 
any effect. 
44. The effect, therefore, depends on the oxidability and 
amalgamating property jointly ; and this points out the modus 
operandi. An amalgamation takes place at the point of con- 
tact, and this brings the oxidable metal into chemical contact 
with the oxide immediately around that point, which is in- 
stantly reduced. The motion of the surface is, however, 
doubtless an electric effect, for when mercury, not recently 
electrified is touched, under acids, 8cc. with metallic wires, 
the effects are not the same. The contact of copper, for in- 
stance, produces an immediate, and even strong radiating 
