in a future stage of the experiment
should not ascend beyond the mica, and cause currents in the liquid on that
side. A strong solution of sulphate of magnesia was carefully poured
without splashing into the basin, until it rose a little above the lower
edge of the mica division _a_, great care being taken that the glass or
mica on the unoccupied or _c_ side of the division in the figure, should
not be moistened by agitation of the solution above the level to which it
rose. A thin piece of clean cork, well-wetted in distilled water, was then
carefully and lightly placed on the solution at the _c_ side, and distilled
water poured gently on to it until a stratum the eighth of an inch in
thickness appeared over the sulphate of magnesia; all was then left for a
few minutes, that any solution adhering to the cork might sink away from
it, or be removed by the water on which it now floated; and then more
distilled water was added in a similar manner, until it reached nearly to
the top of the glass. In this way solution of the sulphate occupied the
lower part of the glass, and also the upper on the right-hand side of the
mica; but on the left-hand side of the division a stratum of water from _c_
to _d_, one inch and a half in depth, reposed upon it, the two presenting,
when looked through horizontally, a comparatively definite plane of
contact. A second platina pole _e_, was arranged so as to be just under the
surface of the water, in a position nearly horizontal, a little inclination
being given to it, that gas evolved during decomposition might escape: the
part immersed was three inches and a half long by one inch wide, and about
seven-eighths of an inch of water intervened between it and the solution of
sulphate of magnesia.

495. The latter pole _e_ was now connected with the negative end of a
voltaic battery, of forty pairs of plates four inches square, whilst the
former pole _b_ was connected with the positive end. There was action and
gas evolved at both poles; but from the intervention of the pure water, the
decomposition was very feeble compared to what the battery would have
effected in a uniform solution. After a little while (less than a minute,)
magnesia also appeared at the negative side: _it did not make its
appearance at the negative metallic pole, but in the water_, at the plane
where the solution and the water met; and on looking at it horizontally, it
could be there perceived lying in the water upon the soluti