CONDITIONS AFFECTING DRAINAGE GENERALLY 19 



tributary to the Housatonic falls 200 feet in 15 miles, or an average of 

 13 feet per mile. 



Conditions affecting the Drainage generally 



The orientation of the present drainage lying within the state of Con- 

 necticut is due to many different causes. Most important of these 

 appear to be : (1) the slope of the plane of erosion, which is now being 

 dissected ; (2) the channels which remain as a legacy from the previous 

 geologic cycle ; (3) geologic structure planes ; (4) the areal distribution 

 of harder and softer rocks, and (5) the formation of drift barriers during 

 the Glacial period. The first and the last mentioned conditions have had 

 a larger or smaller influence upon the general direction of the streams, 

 while the second, third, and fourth conditions have fixed more definitely 

 the orientation of the stream channels. The importance of geologic 

 structure planes in fixing the direction of drainage lines has, in the 

 opinion of the writer, been very much underestimated by the modern 

 school of physiographers. Its importance in the Connecticut region 

 has been treated in another place* and need not be fully discussed here. 



Rocks of the Region 



The rocks of the region in which are the rivers here under considera- 

 tion are gneisses and schists of Cambrian and pre-Cambrian age, with 

 intrusive igneous masses and occasionally narrow belts of crystalline 

 limestone or dolomite. As regards resistance to stream erosion, the chief 

 differences are between the limestone on the one hand and the more 

 resistant gneisses, schists, and igneous masses on the other. The two 

 rivers present somewhat different conditions and should be considered 

 separately. 



The Still River Tributary to the FarminGton 



course of the stream 



As already mentioned, this stream has a course against the prevailing 

 slope of the region. It takes its rise about 2 miles north of the city of 

 Torrington, in a hardly perceptible divide separating its basin from that 

 of the Naugatuck. Its course is north 30 degrees east for about 3 miles, 

 then north 18 degrees to 20 degrees east, in a nearly straight line for 

 about 7 miles, to a series of cascades, which in the succeeding and last 



*The Newark system of the Pomperang valley, by William Herbert Hobbs, Twenty-first Ann. 

 Rep. U. S. Geological Survey, part iii, 1899-1Q00, pp. 137-152 : also The river system of Connecticut, 

 by William Herbert Hobbs, Journal of Geolo6y, vol. ix, 1901, pp. 469-484. 



