Conduction and Distribution of the Galvanic Current. 193 
while the current is passing. 'The mercury for this purpose must 
be very pure. Before the current is established, the globule of 
mercury has its usual spherical form, but as soon as the current 
flows, the globule immediately elongates and moves rapidly to- 
wards the negative pole of the battery. This movement takes 
place when the globule of mercury is at a very considerable dis- 
tance from the wire, and with very pure mercury it will move 
up an inclined side of the dish. This curious movement or pro- 
pulsion appears to be caused by the development of gas about 
the negative end of the globule. One half of the globule be- 
comes clouded and the other half remains clear and bright. The 
clouded half is turned towards the positive pole. In the figure, 
d, d, exhibit the appearance of the globules, and P, N, the positive 
and negative poles of the battery, which in this case are platinum 
wires. Bits of platinum wire laid in the dish as at b, give off 
gases at their extremities, but a peculiar advantage comes from 
using the globule of mercury, as it elongates and turns itself at 
once in the direction of the current passing through it. In the 
figure, quite a number of these globules are represented nearly in 
the positions assumed in the experiment. When the negative 
pole is brought directly over a globule of some size, say from 4 
to 3 inch diameter, it is thrown into a violent agitation and has a 
kind of rotary movement from its rapid elongation in every pos- 
at e, the larger portion being towards the negative pole, and in 
eing at c,c,and here there appeared two little vortices, each 
having a most rapid whirl. 
in place of the pure, a singular and reverse condition follows. 
of the globule is not easily explained. It occurred to me tha 
the zinc contained in the mercury was detained on the oxygen 
°F positive end of the globule and the mercury as it were filtered 
out from it. If this supposition be correct, the hydrogen devel- 
oped at the positive end of the globule by local action, might ac- 
count for the contrary propulsion and reversal of the whole as- 
pect of the globule. “This solution does not however seem to be 
wholly Satisfactory. 
ashington, D. C., Dec. 4, 1850. 
Stcoxp Serres, Vol. XI, No. 32.—March, 1851. 25 
sible direction. Occasionally the globule takes the form as seen ae 
this case both ends of the globule are bright, the clouded portion 
If now some impure mercury containing zinc be introduced — 
