| 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
