rs in the case of
modern submarine forests. For these and other reasons, some of
which are more fully stated in the papers already referred
to, while I admit that the areas of coal accumulation were
frequently submerged, I must maintain that the true coal is a
subaerial accumulation by vegetable growth on soils, wet and
swampy it is true, but not submerged."

I am almost disposed to doubt whether it is necessary to make the
concession of "wet and swampy;" otherwise, there is nothing that I
know of to be said against this excellent conspectus of the reasons
for believing in the subaerial origin of coal.

But the coal accumulated upon the area covered by one of the great
forests of the carboniferous epoch would, in course of time, have
been wasted away by the small, but constant, wear and tear of rain and
streams, had the land which supported it remained at the same level,
or been gradually raised to a greater elevation. And, no doubt, as
much coal as now exists has been destroyed, after its formation, in
this way. What are now known as coal districts owe their importance to
the fact that they were areas of slow depression, during a greater or
less portion of the carboniferous epoch; and that, in virtue of this
circumstance, Mother Earth was enabled to cover up her vegetable
treasures, and preserve them from destruction.

Wherever a coal-field now exists, there must formerly have been free
access for a great river, or for a shallow sea, bearing sediment in
the shape of sand and mud. When the coal-forest area became slowly
depressed, the waters must have spread over it, and have deposited
their burden upon the surface of the bed of coal, in the form of
layers, which are now converted into shale, or sandstone. Then
followed a period of rest, in which the superincumbent shallow waters
became completely filled up, and finally replaced, by fine mud, which
settled down into a new under-clay, and furnished the soil for a fresh
forest growth. This flourished, and heaped up its spores and wood into
coal, until the stage of slow depression recommenced. And, in some
localities, as I have mentioned, the process was repeated until the
first of the alternating beds had sunk to near three miles below its
original level at the surface of the earth.

In reflecting on the statement, thus briefly made, of the main facts
connected with the origin of the coal formed during the carboniferous
epoch, two or three con