266 ANNALS NEW YORK ACADEMY OF 80IENCE8 



other valleys in the Catskills, 8 however, it was partly filled with debris 

 by the continental glacier, so that now the Saw Kill, for the first five 

 miles of its course, has cut its way through a moraine of varying height, 

 70 ft. at Shady, and 40 ft. half a mile below its source. This fact is 

 clearly shown by the character of its bed, which is strewn with huge 

 bowlders of bluestone, sandstone and conglomerate, together with smaller 

 ones of granite and quartz, the harder ones still showing the marks of 

 glacial action. 



Echo Lake 9 



Echo Lake, the only considerable body of water near Overlook, is 

 clearly of glacial origin. It is a shallow pond, about three hundred 

 yards long by two hundred wide, and about eighteen feet deep in the 

 deepest part, situated in the angle formed by the Plattekill and Overlook 

 Mountains, just at the base of the high ridge connecting them. Across 

 this deep valley, the moraine forms a huge natural dam which holds 

 back the water of Echo Lake. The lake is thus bordered on three sides 

 by high wooded ridges; while on the west, extending out over the mo- 

 raine, is a swamp larger than the lake itself. 



As is to be expected from its situation, Echo Lake is apparently de- 

 creasing in size rather rapidly. The swamp on its western side is slowly 

 invading its waters. On this side, too, the lake is being narrowed by 

 the action of its outlet, the Saw Kill, in cutting back through the Glacial 

 drift which forms its bed. The pitch of the Saw Kill, which falls 1200 

 feet in the first four miles of its course, together with the floods men- 

 tioned above, makes this erosion relatively rapid. 



In addition to this cutting away on its lower side, the lake is being 

 rapidly filled in from above. The silt and leaf mold washed from the 

 steep mountain ridges above the lake are deposited in the still water, and 

 the amount of this material is very considerable. On the north and east 

 this deposit forms a bed extending into the lake for more than two hun- 

 dred feet and reaching a depth of four or five feet. Here the deposit is, 

 to a considerable extent, protected from further action of the water by a 

 dense growth of the yellow pond lily, Nymphcea advena, for which the 

 fine silt and leaf mold furnish a favorable substratum. The combined 

 effect of these agencies in reducing the size of the lake is so great as to 

 make it. probable that, at no very distant date, Echo Lake will be oblit- 

 erated. 



Washington, D. C. 



8 John C. Smock : "On the Surface Limit or Thickness of the Continental Glacier in 

 New Jersey and Adjacent States." Am. Jour. Set, vol. 25, pp. 339-350. 1883. 



9 Also known as Sheu's Lake. 



