THE GEOLOGICAL HISTORY OF NEW YORK STATE 27 
point in the lake basin. Thus ‘the streams in the western portion 
of this drainage basin flow north to northeastward, northward in 
the middle portion, and westward to northwestward in the eastern 
portion. Three rivers should be mentioned: the Genesee, with 
its source in the highlands of Pennsylvania, flows northward across 
the entire southwestern plateau; the Oswego, toward the middle of 
the basin, takes one arm (Seneca river) from the west to drain the 
large Finger lakes and another arm from the east to drain Oneida 
lake and part of the Tug Hill plateau; Black river drains the extreme 
eastern portion of the basin, and a number of prominent tributaries 
flow southwestward from well within the Adirondacks to join the 
main stream in the great Black river valley. 
Susquehanna basin. All the waters of the Susquehanna river 
are derived from the Southwestern plateau. The main stream 
(within New York) flows southwestward and together with its 
numerous large tributaries drains much of the eastern portion of 
the plateau region, especially in Otsego county. A number of the 
tributaries rise on the very crest of the Helderberg escarpment and 
within a few miles of the Mohawk river. The Mohawk river is 
fully a thousand feet below the crest of the escarpment, and its 
course is at right angles to that of Susquehanna tributaries. 
The Chemung is the principal tributary from the northwest and 
drains a good portion of the south-central plateau. 
Other drainage basins. The Champlain basin comprises the 
eastern .border of the Adirondacks, including some of the highest 
.and most rugged of those mountains. Nearly all the streams are 
short and most of them descend eastward very rapidly into Lake 
Champlain. 
The Delaware, by means of its upper waters, drains the western 
and southern Catskills and the main stream, after flowing south- 
eastward along the State line between New York and Pennsylvania, 
from Delaware county to Orange county, suddenly swings south- 
westward to pass through the famous Delaware water gap in the 
Kitatinny range. 
The Allegheny river sends out a number of small branching arms 
to drain the extreme southwestern portion of the Southwestern 
plateau. Chautauqua lake (elevation 1338 feet) which lies at the 
very western edge of the plateau and close to Lake Erie, has its 
outlet into the Allegheny. 
The Erie basin contains no river of much consequence, the small 
streams all flowing westward or northwestward across the narrow 
Erie plain and into Lake Erie or the Niagara river. Nearly all 
