chist, and
igneous intrusives. The headwaters of the Still mingle with those of
the Croton system, and its chief southern branch, the Umpog, is
interlaced with the sources of the Saugatuck on a divide marked by
glacial drift and swamps. The explanation of these features involves
not only the history of the Still River system, but also that of the
Housatonic.

In explanation of the present unusual arrangement of streams in
the Still River system, four hypotheses may be considered:

I. Still River valley is the ancient bed of the Housatonic from which
that river has been diverted through reversal caused by a glacial dam.

II. The Housatonic has always had its present southeasterly course,
but the Still, heading at some point in its valley north of Danbury,
flowed initially southward through one of four possible outlets. The
latter stream was later reversed by a glacial dam at the southern end,
or by glacial scouring at the northern end of its valley which removed
the divide between its headwaters and the Housatonic.

III. The Housatonic has always held its present southeasterly course,
and the Still initially flowed southward, as stated above. Reversal in
this case, however, occurred in a very early stage in the development
of the drainage, as the result of the capture of the headwaters of the
Still by a small tributary of the Housatonic.

IV. The Housatonic has always held its present southeasterly course,
but the Still has developed from the beginning as a subsequent stream
in the direction in which it now flows.

The first hypothesis, that the Still is the ancient channel of the
Housatonic, has been advocated by Professor Hobbs, who has stated:

"That the valley of the Still was formerly occupied by a large
stream is probable from its wide valley area.... The former
discharge of the waters of the Housatonic through the Still into
the Croton system, on the one hand, or into the Saugatuck on the
other, would require the assumption of extremely slight changes
only in the rock channels which now connect them.... To turn the
river (the Housatonic) from its course along the limestone
valley some obstruction or differential uplift within the river
basin may have been responsible. The former seems to be the more
probable explanation in view of the large accumulations of drift
material in the area south and west of Bethel and Danbury."

"The structural valleys believed to be presen