Vermont phÅ“nix. [volume] (Brattleboro, Vt.) 1834-1955, 1873-05-09
THE OREGE.v Of CO.sL.


A mistaken impression is somewhat
widely prevalent that, in the coal fields, we
have remains of ancient forests-in other
words, it is supposed that wherever there
was forest in primeval times, there now
exists a coal field of greater or less extent.
In connection with this view, also, the
opinion is entertained that the forests now
in existence will, in the process of time,
and after due geological changes, become
the coal bed of future ages. But although
as we shall presently see, the coal fields
undoubtedly due to the vegetation of for
mer erss, it is far from being the case that
the primeval forest became converted in
general way into coal. Conditions of pc
culiar, and to some extent, exceptional
character were requisite 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 a small portion
Of the thickness of the great geological
group of strata to which they for the most
part appertain. The group is called the
carboniferous, and not uncommonly "the
coal - but even where coal is abundant, it
forms only a minute part of the whole
mass. Thus, ii is estimated, Sir Charles
Lyell tells us, that in South Wales the
thickness of the carbOniferous strata
amounts, in all, to between II, 600 and r.
900 feet, or more than two miles but the
various coal seams do not, according to
Prof. Phillips, exceed in the aggregate one
hundred and twenty feet, or less than one
h,,,, - tI,A Ill T.,
Lancashire the carbonilerous strata occupy
a deptho more than three and h1lfmiles,
with the same relative disproportion in
thickness of the coal seams and that of the
complete series OF strata. Again, in Nova
Scotia, the coal-bearing strata attain
thickness of more than three miles. Here,
no fewer than eighty seams of coal have
been counted (seventy one having been ex-
posed by the action of the sea y but these
seams are nowhere more Than five feet in
thickness, and many are but few inches
thick. Thus it is evident that the forma-
ton of coal can have been in progress but
short portion of the time during which
the carboniferouS series of strata was in
process of deposition. Throughout by far
the greater portion of that time other min
erals were being deposited. II is next to
be noticed that under each coal seam a
stratum of ancient soil exists, in which
there are commonly found the roots of an
cient trees while above the coal there is
commonly layer of shale or sandstone, in
which not unfrcquently the trunks Of those
trees are found either fallen or in their
original position and only partly convert
ed into coal. The bark remains, but is
transmitted into coal the hollow of TIE
trunk, decaying long before the trunk gave
way, is represented by a cast in sandstone
Thus, if we try TO picture to ourselves the
state which existed when such seam
Of coal began TO be covered up by the next
higher deposit, we see that there must have
been trees standing erect above layer of
vegeta bic matter, the roots of them being
imbedded in the soil which forms the de-
post next the coal. The vegetable layer
may probably have been two or three times
as thick as the resulting coal seam, and
were reduced by pressure to their present
thickness but such layers cannot at any
time have reached 10 the branches of the
forest trees. Then the process of gradual
deposition began. This only can happen
when some subsistence 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 in ma
ny cases for a long period of time ; and it
Is equally clear that the formation of the
vegetable layers themselves must have
been process occupying a considerable
time, since tall trees grew before the next
submergence took place. 50 soon as sub
mergence was complete the trees began 10
perish and decay. The stout trunks above
the vegetable layer were broken off and
swept away by the sea. The forest itself,
properly so called, was for the most part
destroyed. 1t was the decaying refuse
of the forest, intermixed with the lower
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.