and the valley made by it; but in a
region of complicated geologic structure, such as western Connecticut,
where rocks differ widely in their resistance to erosion, the same
result is not to be expected. In this region the valleys are commonly
developed on limestone and their width is closely controlled by the
width of the belt of limestone. Even the narrow valleys in the upland
southwest of Danbury are to be accounted for by the presence of thin
lenses of limestone embedded in gneiss and schist.

The opinion of Hobbs that Still River valley is too wide to be the
work of the present stream takes into consideration only the broad
places, but when the narrow places are considered it may be said as
well that the valley is too narrow to be the work of a stream larger
than the one now occupying it. Valley width has only negative value in
interpreting the history of Still River.

2. TRIBUTARY VALLEYS POINTING UPSTREAM

The dominant topographic feature of western Connecticut, as may be
seen on the atlas sheets, is elongated oval hills trending north by
west to south by east, which is the direction of the axes of the folds
into which the strata were thrown at the time their metamorphism took
place. Furthermore, the direction of glacial movement in this part of
New England was almost precisely that of foliation, and scouring by
ice merely accentuated the dominant north-south trend of the valleys
and ridges. As a result, the smaller streams developed on the softer
rocks are generally parallel to each other and to the strike of the
rocks. These streams commonly bend around the ends of the hills but do
not cross them. The narrowness of the belts of soft rock makes it easy
for the drainage of the valleys to be gathered by a single lengthwise
stream. The Still and its larger tributaries conform in this way to
the structure.

On the east side of the Still-Umpog every branch, except two rivulets
1-1/4 miles south of Bethel, points in the normal direction, that is,
to the north, or downstream as the river now flows (fig. 6). The
largest eastern tributary, Beaver Brook, is in a preglacial valley now
converted into a swamp the location and size of which are due entirely
to a belt of limestone. It is not impossible that Beaver Brook may
have once flowed southward toward Bethel, but the limestone at its
mouth, which lies at least 60 feet lower than that at its head, shows
that if such were ever the case it must have been before the