[Illustration: ~Fig. 3.~ Profiles of present and preglacial Rocky River. Elevations at a, b, c and i are from U. S. G. S. map. Elevation at d is estimated from R. E. Dakin's records. Elevations at e, f, g and h are from R. E. Dakin's records. The U. S. G. S. figures for the same are enclosed in parenthesis.] In tabular form the figures, taken from the Danbury and New Milford atlas sheets and from reports of R. E. Dakin, are as follows: Miles Fall in feet per mile Source to Sherman 4 177.5 Sherman to Wood Creek 8 6.25 Wood Creek to Jerusalem 4.5 3.8 Jerusalem to mouth 2.5 69.2 Near Jerusalem, where Rocky River makes its sudden change in grade, there is an abrupt change in the form of the valley from broad and flat-bottomed to narrow and V-shaped. The profile of Rocky River is thus seen to be sharply contrasted with that of a normal stream, which is characterised throughout its course by a decreasing slope. PREGLACIAL COURSE The present profile of Rocky River and the singular manner in which the lower course of the river is doubled back on the upper course are believed to represent changes wrought by glaciation. Before the advent of the glacier, Rocky River probably flowed southward through the "Neversink-Danbury Valley," to be described later, and joined the Still at Danbury, as shown in fig. 4. The profile of the stream at this stage in its history is shown in fig. 3, B. At Sherman a low col separates Rocky River basin from that of the small northward flowing stream which enters the Housatonic about a mile below Gaylordsville. Streams by headward erosion at both ends of the belt of limestone and schist on which they are situated have reduced this divide to an almost imperceptible swell. The rock outcrops in the channel show that the glacier did not produce any change in the divide by damming, though it may have lowered it by scouring. Assume that at one time a divide also existed on the eastern fork of Rocky River, for example near Jerusalem. According to this hypothesis there was, north of this latter divide, a short northward flowing branch of the Housatonic located on a belt of weak rock, similar to the small stream which now flows northward from Sherman, and very like any of the half-dozen parallel streams in the rock mass south and southwest of Danbury, all of which are subsequent streams flowing along the strike. While these stream valleys were growing, the southern ends of the same weak belts of rock were held by southward-flowing streams which united in the broad limestone area now occupied by the city of Danbury. [Illustration: ~Fig. 4.~ Preglacial course of Rocky-Still River. Dotted lines show present courses of the two rivers.]