38 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



ting through the till cover and are not building alluvial cones 

 where they join the lowland. All their features, in fact, are 

 characteristic of normal stream development. 



Throughout the length of the valley, rock outcrops are found 

 near the surface, showing that the changes produced by the 

 glacier were due to scouring rather than to the accumulation of 

 glacial material. Except where stratified drift is collected locally 

 in considerable quantity, the glacial mantle is thin. On the other 

 hand, it has been shown that glacial gouging was not sufficient 

 in amount to affect the course of the stream. The glacier simply 

 cleaned off the soil and rotten rock from the surface, slackening 

 the stream here and hastening it there, and by blocking the course 

 with drift it forced the river at several places to depart slightly 

 from its preglacial course. 



The evidence shows, therefore, that if Still River has suffered 

 reversal, glaciation is not responsible for the change, and thus 

 the first two hypotheses for explaining the history of the valley 

 are eliminated. " there remain for discussion the third and 

 fourth hypotheses; the former being that reversal was effected 

 in a very early stage in the development of the drainage, the 

 latter that no reversal has occurred. The choice between these 

 two hypotheses rests on evidence obtained in the Umpog, Croton, 

 and other valleys of the Danbury region. This evidence is 

 presented in the three following sections, after which the former 

 courses of Still River will be discussed. 



THE STILL-SAUGATUCK DIVIDE 



FEATURES OF THE UMPOG VALLEY 



The valley of the Umpog, which extends from Still River to 

 the source of the Saugatuck near West Redding (fig. 7), is a 

 critical area in the study of the Still River system. It is possible 

 that this valley once afforded an outlet for Still River, and it 

 has been suggested that the Housatonic formerly followed this 

 route to Long Island Sound. The relation of this valley to the 

 former drainage system of the Danbury region demands, there- 

 fore, a careful examination of the features of the valleys occupied 

 by Umpog Creek and the upper waters of the Saugatuck, and of 

 the divide between those streams. 



