M. G. Quincke on a new kind of Electric Current. 457 
Some thirty layers of thin silk stuff were placed over each 
other and attached over the tube A of the apparatus ; the tube 
B was then adapted against the former, and the part separating 
them coyered thickly with sealing-wax. Owing to the wide 
pores of the silk, considerably more water flowed through under 
equal pressure than when the clay plate was employed. The 
linen was used in the same manner. 
The other substances were applied in the form of powder, in a 
glass tube of the diameter of the tubes A and B of fig. 2. The 
ends of these tubes, the length of which varied, according to the 
substance employed, from 20 to 45 millims., were ground flat, 
and oyer them were placed discs of the silk stuff spoken of, to 
prevent the flow of the fluid carrying away particles of the sub- 
stance under examination. In the case of Bunsen’s coal the 
tube was closed with plates thereof. 
Platina was made use of in the spongy form, iron as filings. 
The glass had been reduced to powder on an anvil, Ivory and 
the various kinds of wood were employed in the form of sawdust. 
It was endeavoured in vain to press water through a porous 
plate of wood, for the plate had to be luted in dry; and on 
becoming moist, even if cut perpendicular to the direction of the 
fibres, it warped so much that it broke the sealing-wax or the 
tube. 
The direction of the electric current was not changed by add- 
ing acids or solutions of salts to the distilled water, but it was 
considerably weakened thereby. 
For instance, on using a new clay plate 3°9 millims. thick, 
and pressing distilled water through it, the needle of the multi- 
plier was deflected up to the stop: on the addition of four drops 
of pure hydrochloric acid to a pint and three-quarters of the 
water, the deflection of the needle did not, under the same pres- 
sure as before, exceed 15 or 20 degrees. A further addition of 
twelve drops of acid weakened the electric current so much, that 
a far greater pressure had to be applied to deflect the needle at 
all. If the acid amounted to 16 per cent. of the fluid employed, 
no deflection whatever was observed, even under a pressure of 
three atmospheres. On adding alcohol to the distilled water, 
the deflection of the needle was increased. 
The question arises, what is it that causes these electric cur- 
rents? If the tubes A and B of fig. 1 are luted together without 
any clay plate between them, and a stream of water is passed 
through them, no deflection is observable in the multiplier. 
Hence it is seen that the presence of a diaphragm is necessary 
for the manifestation of an electric current. 
The law that obtains in all these experiments may be stated 
concisely in these terms :— 
