The cover of glacial deposits is generally thin, but marked variations exist. The fields are overspread with coarse till containing pebbles 6 inches in diameter to huge boulders of 12 feet or more. The abundance, size, and composition of the boulders in the till of a given locality is well represented by the stone fences which border fields.
Fig. 1. Present drainage of the Danbury region.
The regional depression which marked the close of the glacial period slackened the speed of many rivers and caused them to deposit great quantities of modified or assorted drift. Since glacial time, these deposits have been dissected and formed into the terraces which are characteristic of the rivers of the region. A form of terrace even more common than the river-made terrace is the kame terrace found along borders of the lowlands. Eskers in the Danbury region have not the elongated snake-like form by which they are distinguished in some parts of the country, notably Maine; on the contrary, they are characteristically short and broad, many having numerous branches at the southern end like the distributaries of an aggrading river. The material of the eskers ranges from coarse sand to pebbles four inches in diameter, the average size being from one to two inches. No exposures were observed which showed a regular diminution in the coarseness of the material toward their southern end. The clean-washed esker gravels afford little encouragement to plant growth, and the rain water drains away rapidly through the porous gravel. Consequently, accumulations of stratified drift are commonly barren places. A desert vegetation of coarse grasses, a kind of wiry moss, and "everlastings" (Gnaphalius decurrens) are the principal growth. Rattlebox (Crotolaria sagittalis), steeplebush (Spiraea tomentosa), sweet fern (Comptonia asplenifolia), and on the more fertile eskers--especially on the lower, wetter part of the slope--golden rod, ox-eyed daisy, birch, and poplar are also present. All the eskers observed were found to be similar: they ranged in breadth across the top from 100 to 150 feet and the side slopes were about 20 degrees. Only a single heavily wooded esker was found, and this ran through a forest region.
The accumulations of stratified drift are distinguished from other features in the landscape by their smoother and rounder outlines, by their habit of lying unconformably on the bedrock without reference to old erosion lines, and by a slightly different tone in the color of the vegetation covering the water-laid material. The difference in color, which is due to the unique elements in the flora of these areas, may cause a hill of stratified drift in summer to present a lighter green color than that of surrounding hills of boulder clay or of the original rock slopes; in winter the piles of stratified drift stand out because of the uniform light tawny red of the dried grass.
[1] The streams and other topographic features of the Danbury region are shown in detail on the Danbury and the New Milford sheets of the United States Topographic Atlas. These sheets may be obtained from the Director of the United States Geological Survey, Washington, D. C.
[2] It was probably not less than 30 miles, for that is the distance from the mouth of Still River, where the Housatonic enters a gorge in the crystallines, to the sea. Fifty-five miles is the distance to the sea from the probable old head of Housatonic River on Wassaic Creek, near Amenia, New York.
[3] Veatch, A. C., Slichter, C. S., Bowman, Isaiah, Crosby, W. O., and Horton. R. E., Underground water resources of Long Island: U. S. G. S., PP. 44, p. 188 and fig. 24, 1906.