No. 30.] STILL RIVER. 41 



these two swamps may be regarded simply as extensions of the 

 Umpog Creek channel, but when the elevations of their bottoms 

 are compared with that of points to the north and south, where 

 the river flows on rock, it will be seen that a profile results which 

 is entirely out of harmony with the present profile of the river. 

 Thus Umpog Creek falls 40 feet at the point where it spills over 

 the rock ledge into the swamp, and if the 45 feet which measures 

 the depth of Umpog Swamp be added, the difference in level is 

 seen to be at least 85 feet. A similar calculation locates the 

 bottom of the smaller swamp near Bethel at an elevation of 340 

 feet above sea-level or on the same level as the bottom gf Umpog 

 Swamp. In a straight line 2*4 miles north of Bethel, Still 

 River crosses rock at a level of 350 feet, or 10 feet higher than 

 the bottom of Umpog Swamp. At Brookfield, 6 l / 2 miles north 

 of the mouth of the Umpog, the Still crosses rock at 260 feet, and 

 4^2 miles farther north, it joins the Housatonic on a rock floor 

 200 feet above sea-level (fig. 8, A). Such a profile can be ex- 



FIG. 8. Profiles of rivers. A. Profile of present Still River and buried 

 channel of Umpog-Still River. B. Profile of preglacial 

 Crotoh- Still River. C. Profile of preglacial Umpog-Still 

 River. Solid lines show the present levels. Dotted lines 

 show preglacial levels. 



plained in either of two ways : glaciers gouged out rock basins 

 in the weak limestone, or the river in its lower part has been 



