rous, and
remain so on drying; these contain intermixed vegetable matter that is
but little advanced in the peaty decomposition. Some peats are almost
entirely free from mineral matters, and on burning, leave but a few _per
cent._ of ash, others contain considerable quantities of lime or iron,
in chemical combination, or of sand and clay that have been washed in
from the hills adjoining the swamps. As has been observed, the peat of
some swamps is mostly derived from mosses, that of others originates
largely from grasses; some contain much decayed wood and leaves, others
again are free from these.

In the same swamp we usually observe more or less of all these
differences. We find the surface peat is light and full of partly
decayed vegetation, while below, the deposits are more compact. We
commonly can trace distinct strata or layers of peat, which are often
very unlike each other in appearance and quality, and in some cases the
light and compact layers alternate so that the former are found below
the latter.

The light and porous kinds of peat appear in general to be formed in
shallow swamps or on the surface of bogs, where there is considerable
access of air to the decaying matters, while the compacter, older, riper
peats are found at a depth, and seem to have been formed beneath the
low water mark, in more complete exclusion of the atmosphere, and under
a considerable degree of pressure.

The nature of the vegetation that flourishes in a bog, has much effect
on the character of the peat. The peats chiefly derived from mosses that
have grown in the full sunlight, have a yellowish-red color in their
upper layers, which usually becomes darker as we go down, running
through all shades of brown until at a considerable depth it is black.
Peats produced principally from grasses are grayish in appearance at the
surface, being full of silvery fibres--the skeletons of the blades of
grasses and sedges, while below they are commonly black.

_Moss peat_ is more often fibrous in structure, and when dried forms
somewhat elastic masses. _Grass peat_, when taken a little below the
surface, is commonly destitute of fibres; when wet, is earthy in its
look, and dries to dense hard lumps.

Where mosses and grasses have grown together simultaneously in the same
swamp, the peat is modified in its characters accordingly. Where, as may
happen, grass succeeds moss, or moss succeeds grass, the different
layers reveal their origin by thei