254 



ON THE HYDROLOGY OF THE BASIN 



south, and away from the great lakes, the basset edges of the formations necessarily front 

 the north, and form a series of steps or terraces facing the north, while down the southern 

 slope of these strata flow all northern subsidiaries of the Delaware, Susquehanna, and Ohio 

 Rivers, almost from the margins of the lakes themselves. 



The lowest escarpment is that of the Niagara, or Middle Silurian Formation, which 

 commences at a slight elevation between Albany and Utica, along the south side of the 

 Mohawk Valley, and crosses the Niagara River at Lewiston. Back of this runs the 

 escarpment of the Helderberg, or Lower Devonian limestones, forming high hills south of 

 the Mohawk, but dying away as it approaches Lake Erie. Still further south, and at a 

 still higher elevation, runs the high escarpment of the upper Devonian sandstone, from 

 the base of Catskill Mountain, on the Hudson, to Lake Erie, along the southern shore of 

 which it ranges away beyond Cleveland into Southwestern Ohio. On the summit of this 

 uppermost platform, and at an elevation of fifteen hundred feet above the sea, and oik; 

 thousand feet above Lake Erie, lie outspread the broad, flat, shallow basins of the bitumi- 

 nous coal field of Pennsylvania and Ohio, constituting the great Appalachian coal basin. 

 Erom the northern part of this coal field the Genesee lliver cuts down through all the 

 escarpments into Lake Ontario. 



Across the soft Lower Devonian terrace, between the middle and upper escarpments, lie 

 in parallel north and south cut valleys, the deep and narrow Lakes Canandaigua, Cayuga, 

 Seneca, Crooked Lake, Auburn, and Skaneateles, all of them, with Lake Oneida, at the 

 foot of the lowest escarpment, drained by the Oswego River into Lake Ontario. But the 

 principal drainage of Southern New York, even from the edge of the Niagara escarpment, 

 is the other way southward, through the upper escarpment, and by deep gorges in the 

 Alleghany Mountains of Pennsylvania, by the Susquehanna River, and Chesapeake Bay, 

 into the Atlantic. In Western New York, the same set of the waters away from Lake 

 Erie carries the drainage into the Alleghany, the Beaver, and other affluents of the Ohio, 

 the head waters of which, therefore, overlook Lake Erie, a thousand feet, from a distance 

 of scarce a dozen miles. There is one spot in Potter County, Pennsylvania, where the 

 same cloud will shed its waters by the Genesee into the Gulf of St. Lawrence, by the Sus- 

 quehanna into the Chesapeake Bay, and by the Alleghany into the Gulf of Mexico. 

 Following the lowest or middle Silurian escarpment across the Niagara River, we see it 

 become the constant limit of the basin of Lake Ontario. 



At Lewiston Heights it is three hundred and sixty feet above the lake. Rising slowly 

 as it enters Upper Canada, it sweeps close around the head of the lake, runs northward, 

 and then northwest along the southwest shore of Georgian Bay, and projects into Lake 

 Huron at Cape Hurdj casting off south westward all the way the waters of the peninsula 

 into Lakes Erie, SI. Clair, and Huron, and forming a well-defined barrier for a separate 



