292 



SCIENCE 



[N. S. Vol. XXXVII. No. 947 



Walnut creeks between Forestville and 

 Silver Creek villages may be mentioned. 

 A very fine illustration is found on the 

 Rochester sheet. The area between the 

 Genesee River and Irondequoit Bay and 

 between Lake Ontario and Iroquois beach 

 ("Ridge Road") is the submerged delta 

 plain of the Genesee River in Lake Iro- 

 quois, now much dissected by present-day 

 streams. The flat stretches about Ironde- 

 quoit Bay bounded by the 400-feet contour 

 are remnants of the silt plain which in Iro- 

 quois time filled the whole breadth of the 

 valley. 



Sandplains built by the ice-border gla- 

 cial drainage are also numerous. These 

 include, for example, the plains on the 

 west side of the Genesee Valley opposite 

 Avon ; the eroded area north and north- 

 west of Geneva ; the mesa-like plains in the 

 Onondaga Valley at South Onondaga and 

 northwest by Cedarvale ; and the plain on 

 which stands the business part of Syracuse. 



The very extensive and conspicuous sand 

 plains and teri'aces on both sides of the 

 Champlain and Hudson valleys, including 

 the great delta plain between Schenectady 

 and Albany contributed by the Iromohawk 

 River, were built in sea-level waters that oc- 

 cupied this depression during the time of 

 the ice removal. 



Clay Plains: Where the static waters 

 were wide and deep so as to permit full 

 assorting of the detritus, more or less clay 

 was spread over the bottom in the more 

 quiet water. The best example is found in 

 the Iroquois Lake basin. In the St. Law- 

 rence Valley east of Cape Vincent, Alex- 

 andria Bay and Ogdensburg are extensive 

 stretches of finely laminated and deep 

 clays, the glacial origin of which is indi- 

 cated by the abundance of lime concre- 

 tions. The heavy clay deposits of the Hud- 

 son Valley belong in this class, but were 

 deposited in sea-level waters. 



Morainal Lakes. — This class includes the 

 hundreds of lakes and lakelets (so-called 

 ponds) now in existence that are scattered 

 over the state and most numerous in the 

 Adirondacks. They owe their existence to 

 the blockade of valleys or drainage courses 

 by glacial drift. The term drift-barrier 

 lakes would be the more accurate name. 

 Great numbers of such lakes have already 

 been obliterated, mostly changed into 

 swamps by marl and peat accumulation or 

 by detrital filling; and all these lakes are 

 doomed to similar ultimate extinction 

 either by filling or draining. 



The Finger lakes probably owe their 

 origin in part, at least in their upper lev- 

 els, to drift barriers. 



Cataract Lakes. — The most singular and 

 interesting lakes in the state lie in the 

 courses of ancient ice-border rivers. These 

 occupy the plunge basins of extinct cata- 

 racts. Niagara to-day illustrates the 

 method in production of a basin or bowl by 

 the excavating work of a large cataract. 

 If Niagara River were to be diverted above 

 the fall so as to extinguish the cataract a 

 rock basin holding a lake would be left in 

 the amphitheater beneath what is now the 

 "Horseshoe" falls. South and east of 

 Syracuse the predecessors of Niagara 

 River plunged over cliffs of the Onondaga 

 limestone in their eastward flow and pro- 

 duced several plunge basins with lakes, 

 two of which outrival Niagara. 



The Jamesville Lake, four miles south- 

 east of Syracuse, is a circle of emerald- 

 green water about one eighth mile in diam- 

 eter, and 60 feet deep, lying in a half- 

 circle amphitheater with perpendicular 

 rock walls 160 feet high. Two and one 

 half miles east of Jamesville Lake, across 

 the Butternut Valley, is Blue Lake, resting 

 in a cataract basin and rock amphitheater 

 equaling the Jamesville in dimensions but 

 not so symmetrical. White Lake, one half 



