The matter in the present bulletin formed the main theme of a thesis on "Drainage and Glaciation in the Central Housatonic Basin" which was submitted in partial fulfillment of the requirements for the degree of doctor of philosophy at Yale University. The field work was done in 1907 and 1908 under the direction of Professor Herbert E. Gregory. I am also indebted to the late Professor Joseph Barrell and to Dr. Isaiah Bowman for helpful cooperation in the preparation of the original thesis, and to Dr. H. H. Robinson for assistance in preparing this paper for publication. DRAINAGE MODIFICATIONS AND GLACIATION IN THE DANBURY REGION, CONNECTICUT -------- By Ruth S. Harvey REGIONAL RELATIONS The region discussed in this bulletin is situated in western Connecticut and is approximately 8 miles wide and 18 miles long in a north-south direction, as shown on fig. 1.[1] Throughout, the rocks are crystalline and include gneiss, schist, and marble--the metamorphosed equivalents of a large variety of ancient sedimentary and igneous rocks. For the purposes of this report, the geologic history may be said to begin with the regional uplift which marked the close of the Mesozoic. By that time the mountains formed by Triassic and Jurassic folding and faulting had been worn down to a peneplain, now much dissected but still recognizable in the accordant level of the mountain tops. Erosion during Cretaceous time resulted in the construction of a piedmont plain extending from an undetermined line 30 to 55 miles north of the present Connecticut shore to a point south of Long Island.[2] This plain is thought to have been built up of unconsolidated sands, clays, and gravels, the debris of the Jurassic mountains. Inland the material consisted of river-made or land deposits; outwardly it merged into coastal plain deposits. When the plain was uplifted, these loose gravels were swept away. In New York, Pennsylvania, and New Jersey, however, portions of the Cretaceous deposits are still to be found. Such deposits are present, also, on the north shore of Long Island, and a well drilled at Barren Island on the south shore revealed not less than 500 feet of Cretaceous strata.[3] The existence of such thick deposits within 30 miles of the Connecticut shore and certain peculiarities in the drainage have led to the inference that the Cretaceous cover extended over the southern part of Connecticut. [Footnote 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.]