Exact measurements of the drift in the upper Still valley are needed in order to establish this hypothesis completely and to plot the old channel, but the position of the rock floor of the former channel extending westward from the Fair Grounds may be fixed approximately. The rock at the assumed divide now stands at 420 feet above sea-level and it is reasonable to assume that ten feet has been removed by glacial scouring and postglacial erosion, making the original elevation 430 feet. The present divide between Andrew Pond and Haines' Pond has an elevation of 460, but the bedrock at this place is buried under 60 feet of drift, so that the valley floor lies at 400 feet. According to these estimates the stream which headed east of the Fair Grounds had a fall of 30 feet before reaching the site of the present Haines' Pond ([fig. 8, B]).
GLACIAL LAKE KANOSHA
When the Croton Branch was beheaded by drift choking up its valley west of Andrew Pond, the ponded waters rose to a height of from 20 to 30 feet and then overflowed the basin on the side toward Danbury. The outlet was established across the old divide, and as the gorge by which the water escaped was cut down, the level of the ponded waters was lowered. At the same time, also, the lake was filled by debris washed into it from the surrounding slopes. Thus the present flat plain was formed and the old valley floor, a local peneplain developed on the limestone, was hidden.
DIVIDES IN THE HIGHLANDS SOUTH OF DANBURY
The mountain mass to the south and southwest of Danbury, including Town Hill and Spruce, Moses, and Thomas mountains, is traversed by a series of parallel gorges trending nearly north and south ([fig. 2]). About midway in each valley is a col, separating north and south-flowing streams. Two of the valleys, those between Spruce and Moses mountains, and Thomas Mountain and Town Hill, form fairly low and broad passes. They were examined to see whether either could have afforded a southerly outlet for Still River.
The rock composing the mountains is granite-gneiss and schist with an average strike of N 30?W, or very nearly in line with the trend of the valleys. The gneiss was found to be characteristic of the high ridges and schist to be more common in the valleys. No outcrops of limestone were found on the ridges, but at two or three localities limestone in place was found on low ground. From the facts observed it is evident that the stronger features of the relief are due to the presence of bodies of resistant rock, whereas the valleys are due to the presence of softer rock. The series of deep parallel valleys is attributed to the presence of limestone rather than schist.