The Cambria freeman. [volume] (Ebensburg, Pa.) 1867-1938, 1873-03-07
ORIGIN OF COAL.

a mistaken impression is somewhat vide
" prevalent that in the coal-felds, we have
the remains of ancient forests-in other
words it is supposed that wherever there
was a 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 beds of the future ages. But, although
as we shall presently see, the coal-te1ds are
undoubtedly due to the vegetation of for
mer eras. it is far from being the case that
the primeval forests became converted in
general way into coal. Conditions of a
peculiar. and to some extent exceptional
character were requisite for the foundation
of coal-fields. If we consider the evidence
given by the coal-tields, We shall see what
these conditions were. The beds or seams
of coal form but a small portion of the thick .
ness of the great geological group of strata
to which they for the most part appertair. ;
! This group is called the carboniferous, and
not uncommOnly 1.-The Coal" but even
| where coal is most abundant, it forms omly
/ a minute part of the whole mass. Thus it
/ has been estimated, Sir CHARLES LyeT tells
us, that in South Wales the thickness of
| the carbonferOuS strata amounts in all, to
between 1900 and 1900 feet (or more
! than two miles J 'but the various coal
seams 90 not" according to Professor
Phillips, exceed in the aggregate 120
feet" or less than One-hundIedth part of
the whole. In North Lancashire the car
boniferous strata occupy depth of more
than three miles. Here, no fever than
eighty seams of coal have been count,
(seventy-one having been exposed by the
action of the sea- but these seams are
nowhere more than five feet in thickness,
and many are but a few inches thick
Thus, it is evident that the formation of
coal can have been III progress but short
portion of the time during which carbon
ferrous series of strata was in process of
deposition. Throughout by far the greater
portion of that time other minerals are be
ing deposited. 1t isnext to be noticed that
under each coal seam a stratum of ancient
soil exists, in which there are commonly
found the roots of ancient trees, while
i
shale or sandstone, in which, not unfre-
quently, tho trunks Of those trees are found
either fallen or still III their original posi-
ton, only partly converted into coal. The
bari. remains, bat is transmitted into coal:
the hollow Of the trunk. decaying long be-
fore he trunk gave way, is represented by
a cast in sandstone. Thus, if we try to
picture to ourselves the state of things
which existed when such a seam of coal
first began to be covered up by the next
higher deposit, we sec that there must have
been trees standing erect above a layer Of
vegetable matter, the roots Of the trees be
ing imbcdded in the soil which forms the
deposit next below the coal. The vegeta-
bic layers may probably have been two or
three times is thick the resulting coal
seam, and were reduced by pressure to their
present thickness but such layers can not
at any time have reached the branches of
the forest trees. Then the process of de
position began. This can only have hap
pened when some subsidence of the soil has
caused it to be submerged to a greater or
/ less depth. We can infer from the depth
of the strata everything the coal seams that
, this state of sUbmergence continued in
many cases for long period of time and
It is equally clear that the formation of the
, vegetable layers themselves have been Il
process occupying o considerable time,
since tall trees grew before the next sub
, meIgence took place. So soon as suLmer-
gence was complete, the tall trees perished
! and began to decay. The stout trunks
above the vegetable layer were broken off
and swept away by the sea. The forest it
SELF probably 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 seams as
it now exists. Among these were the low
er parts Of the trunks of the ancient forest
o.t~~-. T'i.o..o rvuesIIio CUnyrIueu, IKE the
rest of vegetable matter, into COAL Corn
hiU Mdguzine.