From Danbury to its source Still River occupies a valley whose
features are significant in the history of the drainage. Between
Danbury and the Fair Grounds (fig. 1) the valley is a V-shaped ravine
1-1/2 miles long, well proportioned to the small stream now occupying
it but entirely too narrow for the channel of a large river. Along the
valley are outcrops of schist, and granite rock is present on both
sides of the valley for a distance of about one-quarter mile. Part of
the valley is a mere cleft cut in the rock and is unglaciated. At the
Danbury Fair Grounds the valley opens out into a marshy plain, through
which the river meanders and receives two tributaries from the south.
The plain, which extends beyond Lake Kanosha on the west, has a
generally level surface but is diversified in places by mounds of
stratified drift.
Near the railroad a rock outcrop was found which gives a clue to the
nature of the broad lowland. The rock consists mainly of schist, but
on the side next the valley there is a facing of rotten limestone.
This plain, like all the others in this region, is a local peneplain
developed on soluble limestone. A better example could not be found to
prove the fallacy of the saying that "a broad valley proves the
existence of a large river." The plain is simply a local expansion of
a valley which on each side is much narrower. No other river than the
one flowing through it can have been responsible for the erosion, for
the plain is enclosed by hills of gneiss and schist (Pl. III).
At Mill Plain the valley is crowded by ragged rock outcrops which jut
into the lowland. Here the river occupies a ravine cut in till near
the north side of the valley. West of Mill Plain station the valley is
encumbered with ridges of stratified drift, interspersed with heavy
accumulations of till. Near Andrew Pond the true width of the
valley--one-eighth mile--is shown by rock outcrops on both the north
and south slopes. The valley at this point gives no indication of
narrowing toward the headwaters; in fact, it becomes broader toward
the west.
Between Andrew Pond and Haines' Pond is the divide which separates the
waters of the Still system from those of the Croton. It consists of a
jumbled mass of morainal hills, seemingly of boulder clay, that rise
from 50 to 60 feet above the level of the ponds. The divide is thus
merely a local obstruction in what was formerly a through drainage
channel.