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HISTORY OF COLUMBIA COUNTY.31
above the adjacent river, so that it constitutes one of the most striking
points in the scenery of
this part of the valley of the Wisconsin, rising far above all the immediate
surrounding country.
The eastern face of the bluff is precipitous in its upper portion for over
a hundred feet.
At the top of the cliff is a wooded summit, composed in part of glacial drift,
but showing in
one place a few broken layers of limestone, which are in the proper place
and have the proper
character for the buff or lower Trenton limestone. The cliff itself is made
up of fine-grained,
light-coloredto nearly white, friable sandstone, which is composed of angular
and subangular
quartz grains, and possesses a hard, vitrified crust.  In the uppermost part
of the cliff, the hori-
zontal bedding is distinct-the layers being quite thin ; below, however,
it is not plainly percep-
tible; whilst the whole has a sort of a vertically columnar appearance due
to jointing. On the
upper part of the long, wooded slope below are numerous very large sandstone
masses, evidently
fallen from the cliff. At the lower edge of this slope, the Mendota limestone
is partly exposed;
and below it, the upper layers of the Pottsdam with intercalated calcareous
bands. To the right
and left of the line of section, lower, non-calcareous sandstone layers are
exposed, in low cliffs,
rising from the edge of a marsh. At a point on top of the hill, only a few
rods from the sand-
stone cliff, but at an elevation of forty-eight feet above its base, is an
outcrop of much disturbed
Lower Magnesian limestone.
     Numerous points on the surrounding bluffs also show limestone at elevations
above the base
of the sandstone of the Gibraltar cliff, proving the existence of a very
irregular upper surface
to the Lower Magnesian.
      Caledonia'.--This large township is the most interesting, geologically,
of any in the county.
Extending east and west through the central part are the two bold quartzite
ridges known as
the Baraboo Bluffs. In the eastern part of the township, these two ranges
unite, forming a bold
point, around which the Wisconsin River is forced to flow.  The spoon-shaped
space between
the two uniting ranges is filled up by the Potsdam sandstone to a high level.
The same forma-
tion shows in numerous remnants clinging to the outer flanks of both quartzite
ranges, and the
surface rocks over all of rhe rest of the town, except on the tops of the
highest bluffs of the
southern portions, where Madison, Mendota and Lower Magnesian beds all present
themselves.
Very fine and striking sections, showing the unconformity of the Potsdam
sandstone and con-
glomerate to the Huronian quartzite, are to be seen at Derevan's Glen, on
the north side of
Section 18, Township 11 north, Range 8 east, and at Jones' Glen, on Section
22, Township 12
north, Range 8 east, both of which places are very interesting, also, from
a scenic point of view.
                                 RIVERS IN COLUMBIA COUNTY.
      Central Wisconsin may be said to include portions of four distinct
drainage systems-those
 of the Wisconsin, Black and Rock Rivers, flowing southward and westward'
to the Mississippi,
 and that of the Fox River, of Green Bay, flowing northward and eastward
to Lake Michigan,
 and is thus tributary to the St. Lawrence. The direction and. areas of these
river systems are
 more or less directly influenced by the rock structure of the State. Extending
into Wisconsin
 from the Upper Peninsula of Michigan, and forming the central nucleus of
the northern half of
 Wisconsin, is a great mass of ancient crystalline rocks, which is bordered
on all sides by newer
 and undisturbed formations, whose outcropping edges, on the south, east
and west, succeed one
 another in concentric bands.  The central crystalline mass, probably for
the most part never
 covered by later formations, includes the highest land in the State.  It
has a general slope to
 the southward, reaching its greatest elevation-1,100 feet above Lakes Michigan
and Superior
 along its northern edge, within thirty miles of the latter lake. The waters
which fall upon it
 are shed in four different directions-to the north, into Lake Superior;
to the southeast,. into
 Lake Michigan; to the south, into the Wisconsin, which ultimately reaches
the Mississippi,
 and to the southwest, directly into the last mentioned river.
      Wisconsin ]River.-This stream is much the most important of those which
drain the ele-
 vated lands of the State.  Its total length from its source to its mouth
is about four hundred
 and fifty miles. It forms, with its valley, the main topographical feature
of Central Wisconsin.
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