t spontaneously.
Thus yeast, which is a product of the fermentation of beer, is used to
excite and accelerate the fermentation of malt, which is to be converted
into beer, as well as that of paste which is to be made into bread.

CAROLINE.

But if bread undergoes the acetous fermentation, why is it not sour?

MRS. B.

It acquires a certain savour which corrects the heavy insipidity of
flour, and may be reckoned a first degree of acidification; or if the
process were carried further, the bread would become decidedly acid.

There are, however, some chemists who do not consider the fermentation
of bread as being of the acetous kind, but suppose that it is a process
of fermentation peculiar to that substance.

The _putrid fermentation_ is the final operation of Nature, and her last
step towards reducing organised bodies to their simplest combinations.
All vegetables spontaneously undergo this fermentation after death,
provided there be a sufficient degree of heat and moisture, together
with access of air; for it is well known that dead plants may be
preserved by drying, or by the total exclusion of air.

CAROLINE.

But do dead plants undergo the other fermentation previous to this last;
or do they immediately suffer the putrid fermentation?

MRS. B.

That depends on a variety of circumstances, such as the degrees of
temperature and of moisture, the nature of the plant itself, &c. But if
you were carefully to follow and examine the decomposition of plants
from their death to their final dissolution, you would generally find a
sweetness developed in the seeds, and a spirituous flavour in the fruits
(which have undergone the saccharine fermentation), previous to the
total disorganisation and separation of the parts.

EMILY.

I have sometimes remarked a kind of spirituous taste in fruits that were
over ripe, especially oranges; and this was just before they became
rotten.

MRS. B.

It was then the vinous fermentation which had succeeded the saccharine,
and had you followed up these changes attentively, you would probably
have found the spirituous taste followed by acidity, previous to the
fruit passing to the state of putrefaction.

When the leaves fall from the trees in autumn, they do not (if there is
no great moisture in the atmosphere) immediately undergo a
decomposition, but are first dried and withered; as soon, however, as
the rain sets in, fermentation commences, their gaseous products are
impercept