456 M. G. Quincke on a new kind of Electric Current. 
remains in the clay plate. If, then, either by suction at B or by 
some pressure at A, the fluid is driven from A to B through the 
clay plate, there is indicated, at the instant the flow of the fluid 
begins, a deflection of the needles, due to an electric current 
passing from A towards B. ‘The platina plate B, then, on which 
the current strikes last, behaves like the platina plate of a Grove’s 
element. As soon as the passing of the water ceases, the needle 
returns to its place, a polarization-current, however, in a contrary 
sense to the primary current and to the flow of the fluid, being 
called forth. 
On changing the direction of the flow of the water, as by 
means of suction at A, the multiplier indicates an electrical cur- 
rent passing in the fluid from B towards A. 
As with this form of the apparatus the flow of the fluid strikes 
the plates dissimilarly, thus causing a want of precise similarity 
in their conditions, the modification of the apparatus shown in 
fig. 2, by which the flow of the fluid is not directed against the 
platina plates at all, was arranged for the subsequent experiments. 
With this view the tubes A, B of fig. 1 were closed at the end, 
and two narrower tubes, C, D of fig. 2, were adapted to the side 
between the open end of Fie. 2 
the tubes and the platina Pa 
plates. With this arrange- 
ment the fluid against 
the plates remained un- 
changed, while the water 
flowed through C, the diaphragm, and D. 
The pressure employed varied, according to the diaphragm 
used, from a third of an atmosphere to three atmospheres. 
Instead of the clay plate, other porous bodies were placed 
between the tubes A and B of fig. 2; and the multiplier always 
indicated a current coinciding with the flow of the fluid, and 
which lasted as long as that flow did. On its ceasing, there was 
a more or less strong polarization-current in a contrary direction 
to the primary one. 
The substances thus examined were,— 
Silk, Sulphur, 
Linen, Burnt clay, 
Ivory, Tale, 
Glass, Graphite, 
Sand, Bunsen’s coal, 
Fir-wood, Iron, 
Lime-wood, Platina, 
Oak, 
which were applied in the following way. 
