As possible former outlets for the Housatonic, Hobbs has suggested the Still-Umpog-Saugatuck valley or the Still-Croton valley (by way of the East Branch Reservoir)[12], whereas Crosby has suggested the Ten Mile-Swamp River-Muddy Brook-Croton River valley (by way of Webatuck, Wing's Station, and Pawling), or the Fall's Village-Limerock-Sharon- Webatuck Creek-Ten Mile valley.[13] The sketch map, fig. 10, indicates the courses just outlined and one other by way of the Norwalk. The latter is the route followed by the Danbury and Norwalk Division of the Housatonic Railroad. It is natural to assume that the Housatonic might have occupied anyone of these lines of valleys, particularly where they are developed on limestone and seem too broad for the streams now occupying them. Nevertheless, although each of these routes is on soft rock and some give shorter distances to the sea than the present course, it is highly improbable that the Housatonic ever occupied any of these valleys. For had the river once become located in a path of least resistance, such as is furnished by any of these suggested routes, it could not have been dislodged and forced to cut its way for 25 miles through a massive granitic formation, as it does between Still River and Derby, without great difficulty (Pl. IV, A). [Illustration: ~Fig. 10.~ Five suggested outlets of Housatonic River.] An inspection of the larger river systems of Connecticut shows that the streams composing them exhibit two main trends. Likewise, the courses, of the larger rivers themselves, whether trunk streams or tributaries, combine these two trends, one of which is northwest-southeast and the other nearly north-south. The north-south drainage lines are the result of geologic structure, and many broad, flat-floored valleys, often apparently out of proportion to the streams occupying them, have this direction. On the other hand, the northwest-southeast drainage lines across the strike of formations, coincide with the slope toward the sea of the uplifted peneplain whose dissected surface is represented by the crests of the uplands. The valleys of streams with this trend are generally narrow, and some are gorges where resistant rock masses are crossed. The northwest-southeast trends of master streams thus were determined initially by the slope of the peneplain, whereas the north-south trends represent later adjustments to structure.