fluid conductors when transmitting the electric current . 189 
broken, the motion continues as if the electricity still passed; 
but if the mercury be agitated, so as to break the crust col- 
lected at c, the regularity of the motion is disturbed : the 
surface of the mercury is thrown into a kind of fritillation, 
owing to an immense number of minute and very rapid vor- 
tices ; and it is not till after some time that a regular and 
uniform direction of the currents is re-established. 
47. These phenomena demonstrate the existence of a sys- 
tem of currents radiating towards every molecule of the crust 
on the surface. In consequence of this, so long as the latter is 
broken up into small portions and distributed over the whole 
surface, the currents are irregular and undecided ; but as soon 
as these portions begin to be swept together and collected, 
they assume a uniform direction, viz. towards that part where, 
from contact of the vessel or other cause, they meet with no 
counter currents to oppose them. In what manner the crust 
acts is however still a little obscure : in all probability it forms 
a Voltaic combination with the mercury and the liquid. 
48. In reasoning upon the facts detailed in this Paper, we 
have to consider, as probably materially influencing the re- 
sults, first, the vast difference of conducting power between the 
metallic bodies set in motion, and the liquid under which they 
are immersed. This is not unlikely to enter as one of the 
essential conditions of the phamomenon, especially as it ap- 
pears to result from all the experiments, that the peculiar 
action, whatever it be, by which the currents are produced, 
is exerted only at the common surface of the fluids. I have 
never been able to produce the least trace of such currents 
without the presence of a fluid metal. This leads us to con- 
clude that a second essential condition is a perfect immiscibi- 
