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



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 lime- 

 stone, 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 Moun- 

 tain 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 character- 

 istic 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 re- 

 sistant 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. 



The gorge between Spruce and Moses mountains, locally 

 called " Sugar Hollow," narrows southward as it rises to the col, 

 and the rock floor is buried under till and stratified drift to depths 

 of 25 to 50 feet. Nevertheless it is probable that the valley was 

 no deeper in preglacial time than it is now. The plan of the 

 valley with its broad mouth to the north favored glacial scour 

 so that the ice widened and deepened the valley and gave it a 

 U form. Scouring and filling are believed to have been about 

 equal in amount, and the present height of the divide, about 470 

 feet, may be taken as the preglacial elevation. This is 70 feet 

 higher than the rock floor of the divide at West Redding. The 



