Mineral Point tribune. (Mineral Point, Wis.) 1869-1938, 1900-05-17

lHe Wisconsin, with some notes on its
surface geology. 1t is the work of
Rollin d. Salisbury. professor of geo
graphic geology in the University OF
Chicago, and Wallace w. Atwood AS
sistant to Prof. Salisbury 1t is di-
vided into five chapters as follows
General geographic features outline
of the history of rock formations which
show themselves at the surface. gen
eral outline of rain and river erosion,
erosion and the development of stril;-
ing scenic features, the glacial period.
Thlrty-eight illustrative plates are
given, some of them of great beauty.
Some interesting speculations are
made regarding the glacial epoch and
the changes it brought to this region.
Concerning Devils lake in the gla-
cial period the report says that while
the ice was at its maximum stand, il
rose above the moraine ridges at
either end of the lake Between the
ice at these two points there was then
noticeable basin, comparable to that
of the present lake except that the
barriers to the north and southeast
were higher than now. The melting
of the ice supplied abundant water.
and the lake rose above its present
level. The height which it attained is
not known, but it is known TO have
risen at least 80 feet above its present
level. This is indicated by the pres
euce of few diff powders on the
west bluff of the lake at its height
they represent the work of berg or
bergs which at some stage floated out
into the lake with powders attached.
Bowlders dropped by bergs might be
dropped a any level lower than the
highest stand of the lake.
There was another glacial lake on
the east quartzite bluff Like the
Devils lake in glacial time, its basin
was an enclosure between the ice on
the one hand, and the quartzite ridge
on the other. Here the edge OF the
ice, as shown by the position of the
moraine, was affected by a re-entrant
curve, the two ends of which rested
against the quartzite ridge. Between
the ice on the one hand and the
quartzite ridge on the other. a small
lake was formed. It's position is
marked by notable fiat The lake
had a short life, being soou filled up.
The Irregular deposition of glacial
drift gave rise to many depressions
without outlets in which surface
waters collected after the ice had dis
appeared, forming ponds or lakes. SO
abundant are lakes and ponds aud
marshes in recently glaciated regions
and so rare elsewhere, that they CON
stitute one of the more easily recog-
nized characteristics of glaciated re-
gion
After the ice had melted, the mantle
Of drift which is left was sometimes so
disposed as to completely obliterate
preglacial valleys. More commonly il
filled preglacal valleys at certain
points only. In still other cases a val
ley was not filed completely at any
point, though partially at macy In
this last case, the partial filings at
various points constituted dams above
which drainage was ponded, making
lakes. II the dams were not high
enough TO throw the drainage out OF
the valley, the lakes would have their
outlets over them The drift dam be-
ing unconsolidated would be quickly
cut down by the out-howng water.
and the lake level lowered. When
the dam was removed or cut to It's
base the lake disappeared and drain
age followed its preglacial course.
In case the valley was completely
filled. or completely dled at points.
the case was very different. The drain
age ca the drift surface was estab-
lished with reference TO the topogra
ply which obtained when the Ice de-
parted, and not with reference to the
preglacIal valleys. Wherever the pre-
glacial valleys were completely filed
ID postglacial drainage followed lines
which were altogether Independent OF
them When preglacial valleys were
4AAiHf ~ lAAF AAAih III Opus lHt9s the
Dostglacial streams followed them
where they were not filled. only TO
cave them where the blocking occur
red In the former case the present
drainage is through valleys which are
preglacial in some places ard post
glacial n others Thus the drainage
changes effected by the drift af,. the
Zee vas gone. concerned both lakes
and rivers Ia this regicu there are
several illustrations Of these changes
The lake basins Of drift-covered re-
s.ons are Of various types. Some Of
them are altogether in drift. some
partly in drift and partly ia rock. and
some wholly in rock Basins In the
drift were likely 70 be developed when
ever heavy deposits surrounded thin
ones They are especially common Ia
the jepressiona 81 terminal moraines.
Another class Of lake basins occurs
II valleys the basins being partly rock
81 partly drift II thick deposit OF
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