her.

CAROLINE.

But then the Voltaic circle will not be completed; how can any effect be
produced?

MRS. B.

You are right; I ought to have added that the two vessels must be
connected together by some interposed substance capable of conducting
electricity. A piece of moistened cotton-wick answers this purpose very
well. You see that the cotton (PLATE XIII. fig. 2. c.) has one end
immersed in one glass and the other end in the other, so as to establish
a communication between any fluids contained in them. We shall now put
into each of the glasses a little glauber salt, or sulphat of soda,
(which consists of an acid and an alkali,) and then we shall fill the
glasses with water, which will dissolve the salt. Let us now connect the
glasses by means of the wires (e, d,) with the two ends of the battery,
thus . . . .

[Illustration: Plate XIII. Vol. II. page 16.

Fig. 1. Voltaic Battery of improved construction with the Plates
out of the Cells.

Fig. 2. 3 & 4. Instances of Chemical decomposition by the Voltaic
Battery.]

CAROLINE.

The wires are already giving out small bubbles; is this owing to the
decomposition of the salt?

MRS. B.

No; these are bubbles produced by the decomposition of the water, as you
saw in a former experiment. In order to render the separation of the
acid from the alkali visible, I pour into the glass (a), which is
connected with the positive wire, a few drops of a solution of litmus,
which the least quantity of acid turns red; and into the other
glass (b), which is connected with the negative wire, I pour a few drops
of the juice of violets . . . .

EMILY.

The blue solution is already turning red all round the wire.

CAROLINE.

And the violet solution is beginning to turn green. This is indeed very
singular!

MRS. B.

You will be still more astonished when we vary the experiment in this
manner:-- These three glasses (fig. 3. f, g, h,) are, as in the former
instance, connected together by wetted cotton, but the middle one alone
contains a saline solution, the two others containing only distilled
water, coloured as before by vegetable infusions. Yet, on making the
connection with the battery, the alkali will appear in the negative
glass (h), and the acid in the positive glass (f), though neither of
them contained any saline matter.

EMILY.

So that the acid and alkali must be conveyed right and left from the
central glass, into the other glasses, by means