18 A.GBI CULTURAL MANUAL 



From Rochester westward the Lowland itself is divided into 

 two plains Beparated by a bluff 01 escarpment that can be plainly 

 traced. Over this escarpment the waters of Lake Erie descend to 

 Lake Ontario, forming the falls of Niagara. 



The Mohawk valley is a trench 1,000 feet deep, 15 to 20 miles 

 wide, and about 90 miles long. The valley is 445 feet above sea 

 I at Rome, reaching tide level where it joins the Hudson at 

 Troy. 



The surface of Long Island is generally level or gently undulat- 

 V ridge 150 to 200 feet high, composed of sand, gravel, and 

 clay, extends east, and west across the island north of the center. 

 following table shows the area of the state lying at vary- 

 ing altitudes, the location of which may be seen on the accom- 

 panying map. 



Abeas in New York State at Different Altitudes 



Alt'^ ■ Area 



Square miles 



0-100 2.400 



100-500 10,900 



500-1,000 16,100 



1,000-1.500 12,500 



1,500-2,000 5,170 



2,000-3,000 1,700 



3.000-4,000 200 



4.000-5.000 200 



RISERS, LAKES, AND WATERFALLS 



The Btreams of the state may lie divided into those tributary 

 to the Great Lakes and the St. Lawrence, and those flowing in a 

 general southerly direction. In the first division the principal 

 streams are the Genesee, Oswego, Salmon, Black, Oswegatchie, 

 Grass, Raquette, Chazy, Saranac, and Ausablc rivers and their 

 tributaries. The second division includes the Allegheny, which is 

 a p.nrt of the Mississippi River system, also the Susquehanna, 

 d Hudson River systems. 

 ■ral of the little lakes forming reservoirs of the upper 

 il ar< 2,1 >0 to ."..000 feet above tide. The course of the 



upper Hudson is frequently interrupted by falls, but at Troy the 

 river becomes an arm of the sea, where the current is affected by 

 the tide. Being navi ■ huge steamers from Now York Bay 



to Troy, a distance of 150 miles, the river is one of the largest 



