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 present in the crystalline rocks of the uplands due to post-Newark deformation may well have directed the course of the Housatonic after it had once deserted the limestone ... The deep gorge of the Housatonic through which the river enters the uplands not only crosses the first high ridge of gneiss in the rectilinear direction of one of the fault series, but its precipitous walls show the presence of minor planes of dislocation, along which the bottom of the valley appears to have been depressed."[9] The hypothesis proposed by Professor Hobbs and also the second and third hypotheses here given involve the supposition of reversal of drainage, and their validity rests on the probability that the stream now occupying Still River valley formerly flowed southward. The first and second hypotheses will be considered in the following section. [Footnote 9: Hobbs, W. H., Still rivers of western Connecticut: Bull. Geol. Soc. Am., vol. 13, pp. 17-26, 1901.] EVIDENCE TO BE EXPECTED IF STILL RIVER HAS BEEN REVERSED If Still River occupies the valley of a reversed stream, the following physiographic features should be expected: 1. A valley with a continuous width corresponding to the size of the ancient stream, or a valley comparatively narrow at the north and broadening toward the south. 2. Tributary valleys pointing upstream with respect to the present river. 3. The regional slope not in accord with the present course of the river. 4. Extensive glacial filling and ponded waters in the region of the present sources of Still River. 5. Strong glacial scouring at the northern end in default of a glacial dam at the southern end of the valley, or to assist a dam in its work of reversing the river. The evidence of glacial erosion would be a U-shaped valley, overdeepening of the main valley, and tributaries ungraded with respect to the main stream. 1. A VALLEY WIDE THROUGHOUT OR BROADENING TOWARD THE SOUTH