ed
with the isinglass.

CAROLINE.

This precipitate must then be of the same nature as leather?

MRS. B.

It is composed of the same ingredients; but the organisation and texture
of the skin being wanting, it has neither the consistence nor the
tenacity of leather.

CAROLINE.

One might suppose that men who drink large quantities of red wine stand
a chance of having the coats of their stomachs converted into leather,
since tannin has so strong an affinity for skin.

MRS. B.

It is not impossible but that the coats of their stomachs may be, in
some measure, tanned, or hardened by the constant use of this liquor;
but you must remember that where a number of other chemical agents are
concerned, and, above all, where life exists, no certain chemical
inference can be drawn.

I must not dismiss this subject, without mentioning a recent discovery
of Mr. Hatchett, which relates to it. This gentleman found that a
substance very similar to tannin, possessing all its leading properties,
and actually capable of tanning leather, may be produced by exposing
carbon, or any substance containing carbonaceous matter, whether
vegetable, animal, or mineral, to the action of nitric acid.

CAROLINE.

And is not this discovery very likely to be of use to manufactures?

MRS. B.

That is very doubtful, because tannin, thus artificially prepared, must
probably always be more expensive than that which is obtained from bark.
But the fact is extremely curious, as it affords one of those very rare
instances of chemistry being able to imitate the proximate principles of
organised bodies.

The last of the vegetable materials is _woody fibre_; it is the hardest
part of plants. The chief source from which this substance is derived is
wood, but it is also contained, more or less, in every solid part of
that plant. It forms a kind of skeleton of the part to which it belongs,
and retains its shape after all the other materials have disappeared. It
consists chiefly of carbon, united with a small proportion of salts, and
the other constituents common to all vegetables.

EMILY.

It is of woody fibre, then, that the common charcoal is made?

MRS. B.

Yes. Charcoal, as you may recollect, is obtained from wood, by the
separation of all its evaporable parts.

Before we take leave of the vegetable materials, it will be proper, at
least, to enumerate the several vegetable acids which we either have
had, or may have occasion to mention.