THEORIES AS TO DRAINAGE FEATURES 25 



izing the Pomperaug Valley- area a few miles to the east. The deep 

 gorge of the Housatonic (see plate 2, figure 1), through which the river 

 enters the uplands not only crosses the first high ridge of gneiss in the 

 rectilinear direction of one of the fault series, but its precipitous walls 

 show the presence of minor planes of dislocation, along which the bottom 

 of the valley appears to have been depressed 



To turn the river from its course along the limestone valley some ob- 

 struction or differential uplift within the river basin may have been 

 responsible. The former seems to be the more probable explanation in 

 view of the large accumulations of drift material in the area south and 

 west of Bethel and Danbury. 



SOURCES OF THE STREAM 



One of the present sources of the Still is in a high dam of glacial 

 material which chokes the rock channel connecting the Bethel-Danbury 

 valley with the valley of the Saugatuck. The belt of limestone con- 

 tinues through this well marked river cut to the village of West Red- 

 ding. Another branch of the Still meets the Croton system at an almost 

 imperceptible divide in the deep rock channel through which passes the 

 Highland division of the New York, New Haven and Hartford railroad. 

 The former discharge of the waters of the Housatonic through the Still 

 into the Croton system, on the one hand, or into the Saugatuck, on the 

 other, would require the assumption of extremely slight changes only in 

 the rock channels which now connect them. In one case the Highland 

 and in the other the Danbury division of the New York, New Haven 

 and Hartford railroad has taken advantage of these possibly old chan- 

 nels. 



The excursion of the Housatonic into the gneiss-schist area begins at 

 Still River station by a fall of 8 to 10 feet over a shelf of the harder rock 

 (see plate 2, figure 2). This fall may be explained if the channel of the 

 former Housatonic were more deeply cut along the western margin of 

 the gneiss area and an impounding of the water should raise its level to 

 the top of the gneiss obstruction, and thus furnish an outlet, through the 

 fault gorge to the southeast. To assume that the Still river has not been 

 reversed, but has taken its present course against the prevailing slope of 

 the Cretaceous plain of erosion and wholly in consequence of the easy 

 erosion in the belt of limestone, leaves many things to be explained. 



The valley of the Still is much too wide to be explained by erosion of 

 a stream of such small volume and slight declivity. The deep and wide 

 rock channels connecting the branch basin of the Still with those of the 

 Croton and Saugatuck require also an explanation. Again, the rock 



IV— Bull. Geol. Soc. Am.. Vol. 13, 1901 



