CHAPTER 11. 

 PHYSICAL FEATURES. 



AliTITUDE. 



If the basin of Lake Ontario be included, the altitude of the glaciated 

 portion of this region has a rang-e of about 3,000 feet, the lowest part of the 

 Lake Ontario Basin being nearly 500 feet below sea level, while the highest 

 ridges on the Allegheny Plateau are fully 2,500 feet above the sea. This 

 range is found within a distance of about 10<l miles. The shore of Lake 

 Ontario stands about 250 feet above tide, the level of the lake ranging from 

 244.5 to 249 feet, thus reducing the variations of the exposed land surface 

 to about 2,250 feet. The areas embraced between 500-foot contours are 

 approximately shown on PI. I. 



This region attains its highest altitude in the vicinit)^ of the headwaters 

 of the Allegheny and Genesee rivers, in Potter and McKean counties, Pa., 

 and Allegany and Cattaraugus counties, N. Y. These counties include 

 nearly all the area that rises above 2,000 feet, though there are a few square 

 miles in the adjacent portions of Warren Count)', Pa., and Chautauqua and 

 Wyoming counties, K. Y., which rise above that elevation. It will also be 

 observed that the portion of this region rising above 1,500 feet is confined 

 almost wholly to the States of New York and Pennsylvania, there being 

 scarcely 1 square mile of Ohio that is known to rise above this height, while 

 the highest points of Indiana are only about 1,250 feet. The 1,000-foot 

 contour embraces all of western New York and northwestern Pennsylvania 

 except the lowlands that border Lakes Ontario and Erie and a few of the 

 deep valleys. This contour also embraces much of the eastern half of the 

 State of Ohio; also large areas in the western half The main areas standing 

 below 1,000 feet are the Grand River, Scioto, and Maumee basins and a 

 large part of the watershed of the Great Miami River. In Indiana a small 

 area in the northeastern part and a larger area in the eastern part rise 

 above 1,000 feet. With these exceptions only a few isolated ridges and 

 hills, chiefly in the southern part of the State, rise above that contour. The 



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