TOPOGRAPHY. 11 
DRAINAGE. 
“Two-thirds of the state may be considered as forming a 
part of the great Mississippi Valley, while about the north- 
ern third is in the basin of the great lakes. The water-shed 
which divides the streams flowing into Lake Erie from 
those tributary to the Ohio, traverses the state from near 
the north-east corner in a south-westerly direction as a low 
ridge the greatest elevation of which is nowhere more than 
1400 feet above the sea. This water-shed is lower in Ohio 
than in Pennsylvania and New York.” (Wheaton.) 
ELEVATIONS. 
The surface of Lake Erie is 573 feet above the ocean. 
During low water the Ohio river is about 426 feet above the 
ocean at the extreme south-west corner of the state, near 
Gravel Pit, rising to 687 feet at Wellsville in Columbiana 
county. The Ohio river at its lowest point is thus 147 feet 
below the surface of lake Erie. The variations in the general 
surface of the state range from those given above to 1540 
feet, which elevation is reached in Logan county a short dis- 
tance east of Bellefontaine, where two hills rise, the one to 
1500 the other to 1540 feet above tide. A hill in Richland 
county reaches an elevation of 1475 feet. Nowhere else does 
the state reach 1400 feet elevation. It will thus be clear that 
nowhere does altitude play any important part in the distri- 
bution of the birds. 
EROSION. 
The lake Erie drainage plain is generally a gradual slope 
northward, with gorges cut into the underlying shale and 
rock by the larger streams, but without hills of any conse- 
quence. The northern and western parts of the Ohio river 
drainage plain is also level, but growing rougher as the 
streams descend and enlarge, reaching a maximum of rough- 
ness in the south-eastern and southern parts’ of the state. 
The unglaciated region presents the greatest erosion and 
consequently the highest ridges and deepest valleys. Here 
the streams have cut completely through the upper coal 
strata. 
