The mirror. (Stillwater, Minn.) 1894-1925, 1915-03-04

resulting in formation of shale and
slate. Violent and we'll nigh uni
versal convulsions within the earth's
crust marks the close of this period
Both plant and animal life is
more highly developed; especially
plant life.
The disturbances which marked
the close of the Ordovician age ad-
ded the territory adjacent TO Lake
Superior and Huron to the Silurian.
During this age the deepening
water is illustrated by the thickness
of Niagara limestone, superimpos-
ing the ordovician shale and slate, a
condition making Niagra Falls pos
sible.
Along the northern land the ris-
ing sea-foor closed in a series OF
salt water marshes, and ponds, into
which gypsin and saline deposits
were left, giving use to the salt in.
dustry of today.
The plant life was varied and lux
urient. but still of primitive char
acter.
Without changes to mark its
passage on this continent, but with
violent disturbances in Europe. the
Silurion passes on into the Devon
ian.
The outline of Norlh America in
Devonian times was that of a vast
archipelleaeo instead of continent,
one island extending from the Lake
Superior region to Northwestern
Canada, another embracing por-
tions of the Middle Atlantic States,
and New England. others embracing
portions of the Northwest Territory
and group extending from the old
Palaezoic island of Missouri, of
which the Ozark Mountains are the
remains, along the Cincinnati Anti
cline to the Blue Ridge Mountains,
including portions of the states of
Ohio, kentucky and Tennessee,
thence northward to Wisconsin and
Michigan.
The shallow water and its proxi-
nifty to land is shown by the exten-
slve sand stone deposits. which in
Pennsylvania serve as receptacles for
petroleum and natural gas to-day
The most noted feature of Devon
ian times is seen in its marine life.
Replacing many of the earlier types
which have become extinct we find
armored fishes, Sharks, Lampreys,
or ell like fish, Crossopterygli and
Lung fish. representative types of
which still remain.
Because of the tremendous econ
omic importance of the worlds fuel
supply, because it's nearness to the
worlds pocket book; Carboniferious
age, or age of coal, is better known
than any of the Palaeozoie ages. In
this age we see extensive sinking
of the western lands, and a CORE
spending raise along the Appalachl-
an land, into broad costal bog up
on which fiourished dense growth
of tropical vegetation.
The deposition of which. year by
year and accumulation perhaps, by
drift, adding its weight to each pre-
ceding layer to gather upon the slow
ly sinking bottom, built up bogs, of
pure vegetable formation, of immense
thickness. This, subject to the pres
sure from above, and to the heat
within, has transformed it into coal.
In places the gradual formation
has been temporarily arrested as
the Interpolation layers of sandstone
and shale between those of the coal
shows. Oscillations and deposition
would again raise it above the sur
face into a mush, when growth and
decay would be resumed. 1t must
not be assumed the worlds supply of
coal began and under simultaneously
with carboniferous. For it did not.
Coal is in the process formation to-
day in isolated bogs here and there.
in which growth, deposition, and
decay went on, is shown by the scat
tered coal fields through the world.
In contrast to the Appalachi-
an land is seen In the west, where
the deepening sea, abounded in Pa
laeozoie life, has laid down exten-
sive records in fields of limestone,
but no coal.
The Permain age was one of trans
ition. The deep waters of Carbon
ferrous seas were replaced by the
shallow Permain seas. reflected in the
changed deposition, from limestone,
to sandstone and snale, and the large
area over which no Permian rock
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