The Grit-advocate., 1903-01-02
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The Origin Of clays.


before the Wisconsin Clay Workers
Association. said:
1t may be interesting to you to have
me tell you something In regard to the
origin Of clays. l am very certain
that many of you are familiar with
this SUBJECT, but 1t will do no harm for
me to make an attempt to place be-
fore you in a somewhat systematic
manner the origin of clays. In this
connection will say that all clays.
whether they occur along the lake
shore. along some stream channel
yonder in central Wisconsin. in the
vicinity of Eau Claire in the form of
shales, or at Stockbridge and Oakf1eld
in the form of shales, no matter where
they occur, they are the result of the
breaking down, the decomposition OF
igneous rocks, rocks which have been
formed from molten material, solidi-
fed within or at the surface of the
earth. 1t is supposed that all the ear
liest rocks formed were of igneous
origin. We have two classes Of rocks,
the igneous and the sedimentary
rocks. The sedimentary rocks have
been derived from the igneous rocks
largely, through the mechanical break
ing down of the later rocks, and thus
the sedimentary rocks, sandstone,
limestone and slate which covers a
large portion of Wisconsin are often
spoken of as secondary; simply mean
ing by the term secondary that they
have been derived from some other
rock If this should be carried still
farther it might be said that the clays
are sometimes tetiary rocks. They
may be either tertiary or depending
upon whether or not they have been
derived directly from the igneous
rocks. If they have been derived
directly from the igneous rocks they
will be secondary, and if they have
been derived by the breaking down
of the sedimentary rocks they may be
known as tertiary. In this connec-
tion l speak of the clays as rocks from
the fact that scientifically any accum-
solidified or not, comes in under the
head of the term rock, that is, the
scientific application of the term
rock.
Clays may be conveniently divided
into two classes known as residual
and transported. A residual clay is
one that results from the decomposi-
tion of a rock in place. Take for ex-
ample thousand acres of land in the
northern part of Wisconsin,, covered
with naked rocks, and let it be sub.
jected to the atmospheric agencies
for an indefinite term Of years and
you will have the rocks broken down
into loose earthly mass. The rain
water seeps into the rock and the
breaking down of that rock simply
means that certain constituent ele-
ments are separated from the miner
ais which compose that rock and are
carried off by the underground water.
That part of the rock which remains
is known as a residual clay, provided
the rock originally contains the clay
constituent.
In great many cases the small par
ticles that have been broken from the
different rocks which cover the sur
face Of the earth are picked up by
the water which flows off from the
surface and carried into the streams
and by them into the oceans, lakes
or flood plains of the streams, and
there deposited. These particles are
sorted out according to their size and
specific gravity, particles of like size
and the same specific gravity being
accumulated in one place.-Farmers'
Review.