The Columbia herald. [volume] (Columbia, Tenn.) 1850-1873, 1873-04-04
The Origin of Coal.


a. mistaken impression is somewhat
widely prevalent that, in the coal fields,
we have the remains of ancient forests
lin other words, it is supposed that
wherever there was forest In primeval
times, there now exists coal field of
greater or less extent. In connection
with this view, also, the opinion is
entertained that the forests now in ex-
istence will, in the process of time, and
after due geological changes, become the
coal beds of future ages. But although,
as we shall presently see, the coal fields
are undoubtedly due to the vegetation
of former eras, it is far from being the
case that the primeval forests became
converted in a general way into coal.
Conditions of peculiar, and to some
extent exceptional character, were re-
quisite for the formation of coal fields.
If we consider the evidence given by the
coal fields themselves, we shall see what
these conditions were. The beds or
seams of coal form but small portion
of the thickness of the great geological
group of strata to which they for the
most part appertain. This group is
called the carboniferous and not uncom-
monty "the eoal"; but even where coal
is abundant, it forms only minute part
of the whole mass. Thus it is estimat-
ed Sir Chas. Lyell tells us that in
South Wales the thickness of the
carboniferous strata amounts, in all, to
between II, 900 and II, 900 feet, or more
than two miles; but the various coal
seams do not, according to Prof. Phil
lips, exceed the aggregate 100 feet, or
less than one-hundredth part of the
whole. In North Lancashire the car
boniferous strata occupy a depth of
more than three and half miles, with
the same relative disproportionin thick
ness of the coal seams and that of the
complete series of strata Again, in
Nova Scotia, the coal bearing strata at
tain a thickness of more than three
miles. Here, no fewer than eighty
seams of coal have been counted Seventy
one having been exposed by the action of
the sea-; but these seams are nowhere
more than five feet in thickness, and
it is evident that the formation of coal
can have been in progress but a short
portion of the time, during which the
carbOniferOus series of strata was in pro-
cess of deposition. Throughout by far
the greater portion of that time other
minerals were being deposited. 1t is
next to be noticed that under each coal
seam q stratum of ancient soil exists, in
which there are commonly found the
roots of ancient trees; while above the
coal there is commonly layer of shale
or sandstone, in which not unfrequent-
~ the trunk of those trees are found
either fallen or in their original position,
and only partly converted into COAL
The bark remains, but is transmitted in
to coal the hollow of the trunk, decay
ing long before the trunk, gave way, is
represented by cast in sandstone
Thus, if we try to picture to ourselves
the state of things which existed when
such a seam Of coal began to be covered
up by the next higher deposit, we see
that there must have been trees stand
ing erect above layer of vegetable
matter, the roots of the trees being i'm
bedded in the soil which forms the
deposit next the coal The vegetable
layer may probably have been two or
three times assthick as the resulting coal
seam, and were reduced by pressure to
their present thickness; but such layers
cannot at any time have reached to the
branches of the forest trees. Then the
process of gradual deposition began
This only can happen when some sub
sidence of the soil had caused it to be
submerged to greater or less depth.
We can infer from the depth of the
strata everything the coal seams that this
state of submergence continued inmany
cases for long period of time and it
is equally clear that the formation of
the vegetable layers themselves must
have been a process occupying a con-
siderable time since tall trees grew be-
fore the next submergence took place.
So soon as submergence was complete,
the tall trees persisted and began to
decay. The stout trunks above the
vegetable layer are broken off and swept
away by the sea. The forest itself,
properly so-called, was for the most
part destroyed. It was the decaying
refuse of the forest, intermixed with the
lowlier growths, which formed the coal
seam as it now exists. Among these
were the lower parts of the trunks of
ancient forest trees. These became
converted, like the rest of the vegetable
matter, into coal.