The prison mirror. [volume] (Stillwater, Minn.) 1887-1894, 1891-08-06
SURROUNDING GEOLOGICAL STRUCTURE.
(Report for Glass c. by E. L. H.

(RepOrt for Glass c. by E. l.. H.
P rof. Wnchell, in his volume entitled Walks
and Talks in the Geological Field" gives the fol-
lowing explanation, or theory of the formation Of
limestone, viz: During the Cambrian Age the hot
acid waters of the ocean, coming in contact with
the silcates. which composed the fire formed
crust Of the earth, the silicates were decom.
posed and chlordes and carbonate
form ed and among these carbonate of lime and
carb onate of magnesia. The first is called lime.
stone and the second is generally m liked with the
first forming dolomite or what is better known in
the United States as magnetism limestone. With
this short explanation we will proceed to view
some of the surrounding structure.
Commencing with the bluff on the south as we
stroll along; at the bottom we find sort Of i'm
pure stratifed limestone averaging two feet in
thickness with a blush tint, which upon ex.
posure to air and water is disposed to crumble
and is soft that it can easily be scratched with
knife. In ascending order we next perceive a
white, friab!e and loose sandstone which can
readily be excavated with a shovel; the layer
averages about fifteen feet in portions of which it
changes its color to brown tint but this is no
doubt due to the presence of water. which is
stro ngly impregnated with iron and magnesia as
the water in the springs of the immediate vicinity
all contain more or less of these two minerals
Above the white stone comes a layer of stratifed
stone in beds of two and three inches but seems
to be mixed with the sandstone lying beneath
varying in color from buff to Ii ht drab. From
what have been able to ascertain this layer had
considerable thickness in the eastern division of
the bluff and large portion of the first hundred
feet of the wall was constructed from the stone
found there. This is the well known lower mag.
nesian limestone, or dolomte; it is harder than
most granite and forms, owing to the homogeneity
and compactness of its texture and composition,
and its remarkable resistance to atmospheric in
duence, of the best building stones to be
found in the United States 1t is available in all
kinds of structure. This Institution is almost
eirely built of this limestone Next comes another
stratifed sandstone formation, yellow in appear
ance of ten feet IN thickness, somewhat harder
than the white stone referred to. Above all
comes the drift with which we all have become so
familiar consisting of clay. sand pebbles, etc.. red
in color and from ten to fifteen feet in depth.
What kind of structure have on the west
cannot be ascertained as everything has been
covered by the drift and the embankment the
latter the result of the attempts to establish a
street. high above our level. The ravine in which
we situated seems to have formerly been a
part of the bed. of Lake st. Croix and was the
drain for the surrounding bluffs which form a
watershed. The drift that was excavated few
years ago the result of sedimentation as
the water sought an outlet. and it appears to me
that the attempts to establish street across our
western border. thus obstructing natural water
cha mel. will result in failure attended by
nous cost, as no doubt the residents of the city
have by this time discovered.
On the north the same general characteristics
are met with as on the south. with the exception
that high above the drift can be seen an outcrop.
ping of the magnetism limestone forming the pre-.
cpitous bluff, showing that there occurs fault
somewhere in the formation If the theory that
the lime rock was deposited during the Cambrian
Age is correct, we must conclude that the St.
Croix gorge in which located. was the first
portion Of the Mississippi valley to take place
and shape, avenue of drainage from the
Paleozoic continent to the surrounding Paleo
9oic ocean.
Nhn ofx,