102 Topographical Sketch of the State of New- Yorh 

 From Lake Erie to the head of the rapids, distance 20 miles, fall 15 feet. 



Thence t^Lake Ontario, 7 ™2 



Total, 35 miles, fall 336 feet. 



The annexed table of elevations and distances, through the 

 whole extent of the St. Lawrence basin, in connexion with the ta- 

 bles already given, will show its depression below the mountain 

 surface of the country. 



No. XL 



Table of Ascents and Distances through the St. Lawrence basin, 

 from the gulf of St. Lawrence to the western angle of Lake 

 Superior. 



The slopes of the lower subdivision of the St. Lawrence basin, 

 which descend to the shores of Lake Ontario, occupy a consider- 

 able portion of the state of New-York. Beginning near the east- 

 ern extremity of Lake Erie, the boundary or edge of this sub-basin 

 may be traced on the map along the heads of streams falling into 

 Lake Ontario, through the southern part of the counties of Erie 

 and Genessee, to the valley of the Genessee river, which is an arm 

 of the St. Lawrence basin, stretching up into the high lands of 

 Pennsylvania. From the Genessee river, the edge of the basin 

 curves to the southeast around the southern extremities of Seneca 

 and Cayuga lakes, including the four smaller lakes which lie a 

 little to the west of these. The deep ravines in which are situat- 

 ed Seneca and Cayuga lakes may also be considered as arms or 

 branches of the principal basin, separated from each other by a 

 high ridge. From the head of Cayuga lake, the edge of the basin 

 turns suddenly to the north along the lake, and passes in a north- 

 easterly direction through the northern part of Cortland county, a 

 little south of Skeneateles lake, in nearly a straight line to the 

 Little Falls on the Mohawk river. Here it suffers, for the first 



