24 W. H. HOBBS — STILL KIVEKS OP WESTERN CONNECTICUT 



side of the limestone belt. The course of the Housatonic from this point 

 across the uplands of harder rocks, despite the fact that the easier course 

 to the sound is now apparent in the topography, introduces special diffi- 

 culties of explanation. 



THEORIES AS TO CERTAIN FEATURES OF DRAINAGE 



Kiimmel* has suggested the theory that the Housatonic is here a 

 stream consequent upon post-Triassic tilting and faulting, the assump- 

 tion being apparently that its channel, when conditions determined its 

 present course, was still maintained by the river during the uplift of the 

 land. 



Crosby f has apparently adopted the same view for this and other ex- 

 cursions of the Housatonic into the gneiss uplands. While admitting 

 the possible adequacy of this hypothesis, I am inclined to find the ex- 

 planation rather in the influence of structural valleys in the harder 

 rocks, taken in connection with that of obstructions formed during the 

 Glacial period. The evidence seems to me to point strongly in the 

 direction of an earlier course for the Housatonic through the valley of 

 the Still to some other valley through which its waters reached the sound. 

 In a paper J read before this Society in June, 1900, I suggested this ex- 

 planation and mentioned the Saugatuck river as one through whose 

 valley the waters of the Housatonic may have been conducted to the 

 sound. At about the same time Crosby § suggested that the waters of 

 the Housatonic probably once (lowed from near Merwinsville through the 

 valley of the Swamp river into the Croton basin. . That the valley of the 

 Still was formerly occupied by a large stream is probable from its wide 

 valley area. 



As already stated, the structural valleys believed to be present in the 

 crystalline rocks of the uplands due to post-Newark deformation may 

 well have directed the course of the Housatonic after it had once deserted 

 the limestone. The evidence for the existence of nearly vertical planes 

 of dislocation and of the movement of included orographic blocks along 

 them within the area of western Connecticut has been included in the 

 author's papers above referred to.|| It will suffice to state here that the 

 principal elements of the river's zigzags within the gneiss belt agree 

 closely with the well determined series of vertical fault planes character- 



* Henry B. Kummel : Some rivers of Connecticut, Jour. Geol., vol. i, 1893, p. 381. 



t W. O. Crosby : Notes on the geology of the sites of the proposed dams in the valleys of Housa- 

 touic and Ten-mile rivers, Technology Quarterly, vol. xiii, June, 1900, p. 121. 



| The present paper, which, slightly expanded, was read by title at the Denver meeting, August 

 27, 1901. 



§ Loc. cit. 

 Twenty-first Annual Report U. S. Geological Survey, 1899-1900, part iii, pp. 160. 



