pe of the
uplifted peneplain and is antecedent in origin. The old headwaters
extended northwest from the turn in the river near Bull's Bridge,
whereas that part of the river above Bull's Bridge was initially a
minor tributary. This tributary, because of its favorable situation,
in time captured all the drainage of the extensive limestone belt to
the north and then became part of the main stream. The lower
Housatonic, therefore, has always maintained its ancient course
diagonal to the strike of formations, and differential erosion, which
reaches its maximum expression in limestone areas, is responsible for
the impression that the Still River lowland and other valleys west of
the Housatonic may once have been occupied by the latter stream.

[Illustration: ~State Geol. Nat. Hist. Survey Bull. 30. Plate IV.~
A. View down the Housatonic Valley from a point one-half mile
below Still River station. Pumpkin Hill, a ridge of resistant
schist and quartzite, stands on right. A small island lies in
the river.
B. Part of the morainal ridge north of Danbury. Till capped by
stratified drift one mile north of Shelter Rock.]

[Footnote 12: Hobbs, W. H., Still rivers of western Connecticut: Bull.
Geol. Soc. Am., vol. 13, p. 25, 1901.]

[Footnote 13: Crosby, W. O., Notes on the geology of the sites of the
proposed dams in the valleys of the Housatonic and Ten Mile rivers:
Tech. Quart., vol. 13, p. 120, 1900.]

GLACIAL DEPOSITS

BEAVER BROOK SWAMP

A broad belt of limestone extends along the eastern side of the
granite ridge of Shelter Rock and in preglacial time formed a
broad-bottomed valley whose master stream had reached old age. When
the glacier came it hampered the drainage by scooping out the rock
bottom of the valley in places and by dropping deposits at the mouth
of Beaver Brook valley, thus forming Beaver Brook Swamp or "The Flat,"
as it is called (fig. 6).

Among the deposits at the southern end of Beaver Brook Swamp is
considerable stratified drift in the form of smoothly rounded hills or
kames, which are situated both on the border of the valley and in the
swamp. Till containing medium-sized boulders of granodiorite-gneiss
occurs along the road which borders the east side of the densely
wooded swamp.

Along the northeastern border of the swamp is a flat-topped terrace of
till, perhaps a lateral moraine, through which a small stream heading
to the north has cut a