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



2. TRIBUTARY VALLEYS POINTING UPSTREAM 



The dominant topographic feature of western Connecticut, 

 as may be seen on the atlas sheets, is elongated oval hills trend- 

 ing north by west to south by east, which is the direction of the 

 axes of the folds into which the strata were thrown at the time 

 their metamorphism took place. Furthermore, the direction of 

 glacial movement in this part of New England was almost 

 precisely that of foliation, and scouring by ice merely accentuated 

 the dominant north-south trend of the valleys and ridges. As a 

 result, the smaller streams developed on the softer rocks are 

 generally parallel to each other and to the strike of the rocks. 

 These streams commonly bend around the ends of the hills but do 

 not cross them. The narrowness of the belts of soft rock makes 

 it easy for the drainage of the valleys to be gathered by a single 

 lengthwise stream. The Still and its larger tributaries conform 

 in this way to the structure. 



On the east side of the Still-Umpog every branch, except two 

 rivulets ij4 miles south of Bethel, points in the normal direction, 

 that is, to the north, or downstream as the river now flows (fig. 

 6). The largest eastern tributary, Beaver Brook, is in a preglacial 

 valley now converted into a swamp the location and size of which 

 are due entirely to a belt of limestone. It is not impossible that 

 Beaver Brook may have once flowed southward toward Bethel, 

 but the limestone at its mouth, which lies at least 60 feet lower 

 than that at its head, shows that if such were ever the case it must 

 have been before the north-flowing Still River had removed the 

 limestone north of Beaver Brook Swamp. 



On the flanks of Beaver Brook Mountain are three tributaries 

 which enter the river against its present course. Examination 

 of the structure reveals, however, that these streams like those on 

 the east side of the river are controlled in their direction by the 

 orientation of the harder rock masses. The southward flowing 

 stream four miles in length which drains the upland west of 

 Beaver Brook Mountain has an abnormal direction in the upper 

 part of its course, but on reaching the flood plain it takes a 

 sharp turn to the north. Above the latter point it is in line with 

 the streams near Beaver Brook Mountain and is abnormal in 

 consequence of a line of weakness in the rock. 



