No. 3O.] ^SUGGESTED COURSES OF HOUSATONIC RIVER. 53 



maintained its ancient course diagonal to the strike of formations, 

 and differential erosion, which reaches its maximum expression 

 in limestone areas, is responsible for the impression that the Still 

 River lowland and other valleys west of the Housatonie may once 

 have been occupied by the latter stream. / J^ . ^ 



GLACIAL DEPOSITS 

 BEAVER BROOK SWAMP 



A broad belt of limestone extends along the eastern side of 

 the granite ridge of Shelter Rock and in preglacial time formed 

 a broad-bottomed valley whose master stream had reached old 

 age. When the glacier came it hampered the drainage by scoop- 

 ing out the rock bottom of the valley in places and by dropping 

 deposits at the mouth of Beaver Brook valley, thus forming 

 Beaver E>rook Swamp or " The Flat," as it is called (fig. 6). 



Among the deposits at the southern end of Beaver Brook 

 Swamp is considerable stratified drift in the form of smoothly 

 rounded hills or kames, which are situated both on the border of 

 the valley and in the swamp. Till containing medium-sized 

 boulders of granodiorite-gneiss occurs along the road which 

 borders the east side of the densely wooded swamp. 



Along the northeastern border of the swamp is a flat-topped 

 terrace of till, perhaps a lateral moraine, through which a small 

 stream heading to the north has cut a V-shaped ravine. A lobe 

 of fine till extends into the valley from the northeast and narrows 

 the outlet. 



Between the railroad and highway, which cross the northern 

 end of the swamp, is an irregular wooded eminence of rock, 

 partly concealed by a veneer of drift. Between this knoll and 

 Shelter Rock are heavy deposits of sand in the form of a short, 

 broad terrace with lobes which point into the Still River valley. 

 A similar terrace is found to the northwest on the opposite side 

 of the valley. 



At the northern end of Shelter Rock along the blind road lead- 

 ing to the summit is a peninsula-like body of drift which contains 

 huge granite boulders mixed here and there with pockets of sand 

 and gravel. Stratified drift was found at the foot of the hill, and 



