The Virginia enterprise., 1909-07-09


gions. where there was not depth Of
water enough to destroy the vegeta-
ton or to admit of the intrusion of
gravel, sand and mud, which, brought
in from surrounding highlands, would
have rendered it too impure for use.
The character Of the vegetation which
supplied these great accumulations of
coal is amply; shown - - the fossil
forms which appear, especially near the
top and bottom Of the4 coal seams.
while in some cases the entire stumps
of trees are found still standing in
place, with their roots s,penetrating into
the under clay which, supported the
vegetation.
In Nova Scotia there are found no
less than 76 seams of coal separated
by beds of sandstone and shale. Each
of these beds indicates a change of
level which took place in the region
during its accumulation. During the
accumulation of the coal the swamp
was so shallow that no currents of wa
ter would carry into it sand and gravel
to interfere with the growth or bury
it. But after certain amount of veg
etable deposits had accumulated, there
was subsistence of the area, allowing
access to currents of water carrying
sediment sufficient to bury the deposit
of coal, and furnish the basis for the
growth of vegetation in another swamp
on top of the accumulated sediment,
and so the process went on indefinite
ly, as long as the climate continued fa-
vorable, and these changes of level
continued to proceed with the appro-
pirate rate of rapidity.
The fossil plants of the coal period
seem to indicate that the climate was
at that time warm and moist and uni.
form, while the amount of coal accu-
mulated shows that the air was much
more fully charged with. carbonic acid
gas than it is at the present time. OF
the coal plants of Great Britain about
half were ferns, many of them grow
ing to the size of trees, the most of
which are tropical species. Indeed,
during the coal period in Great Britain
the proportion of ferns there to the
other plants was far greater than it
is in the tropics at the present day,
while tree ferns are now wholly con-
fined to tropical regions. Abundant
tropical forms of vegetation are found
In the coal seams in Greenland and on
Melville island as far north as the
seventy-fifth degree of latitude: in
deed, everywhere during the coal Pc
riod the climatic conditions not only
of the temperate zone, but of the arc
tic lands, were closely similar to those
of the present torrid zone.
But, for mans use, it was necessary
not only to have coal accumulate: it
must be preserved for distant ages and
brought within his reach. If the Mis-
sissippi basin had remained forever
below the ocean level, it's stores of &C.
cumulated coal would have been un-
available. But, through causes which
we can but dimly comprehend, at the
close of the coal period the land all
over that area, which had up to that
time been slowly sinking, reversed its
movement and began to rise. The ele-
vatlon was produced by lateral pres
sure, which folded up the Allegheny
mountains and produced a number of
d1minutive waves, so to speak, in the
surface of the land extending to the
center of the Mississippi basin.
But no sooner was this land Gle.
waited above the sea than erosive agen-
c1es went to work to dissect it and
to remove it's more elevated portions.
Consequently it is estimated that more
than nine-tenths of the coal which was
originally deposited over central and
eastern Pennsylvania, has been car
ried away by the rivers, atd hopeless
ly scattered over the bottom of the
sea, while the one-tenth which remains
is so folded up in the rocks that it
is obtained with great difficulty. In
the more central portions of the Mis-.
sissippi valley, however, the disturb.
ance of the strata has been less. and it
Is comparatively simple matter to
obtain the rich deposits.