the Wabash river, and from thence the state of Illinois ex- 

 tends to the mouth. 



Parts. The Ohio is naturally divided into three parts, con- 

 taining each two sections, the head branches Alleghany and 

 Monongahela form the two sections of the first part. The se- 

 cond or upper part lies between their junctions and the falls, 

 being divided into two sections by Letart's rapids; while the 

 third or lower part includes the space below the falls, the first 

 section of which terminates at the end of the narrow valley above 

 Troy in Indiana, and the second which includes the broad and 

 ilat valleys reaches to the the mouth. The upper part of the 

 river is the longest, being about seven hundred miles long. 



Breadth. At Pittsburgh the Ohio is about one quarter of a 

 mile wide, above the falls and near the mouth it is over one 

 mile: its average breadth may be reckoned at half a mile or 

 rather two thousaud five hundred feet. 



Depth. Very variable according to places and times. The 

 mean depth at low water may be rcckoDcd at three feet, and at 

 high watejt at about thirty feet. Average medium fifteen feet. 



Velocity. The current of the Ohio is generally gentle, ex- 

 cept at the falls and ripples. Its average at low water may be 

 stated at two miles an hour and at high water at four miles an 

 hour. 



Bulk. The quantity of waters flowing in the Ohio may be 

 therefore calculated, upon a general medium of the above 

 breadth, depth, and velocity, at about forty millions of cubic feet, 

 during an hour at low water, and at more than eight hundred 

 millions of such feet at high water. Average medium three 

 hundred and eighty millions in an hour, nine thousand one hun- 

 dred and twenty millions in a day, and more than three millions 

 of millions of feet in one year. 



Waters. They are slightly turbid, and become much moie 

 so in the rises. At a low stage they are almost clear, and at all 

 times very salubrious. The Monongahela has the same charac- 

 ter, while the Alleghany is almost perfectly clear. The turbidi- 

 ty of the waters is produced by very fine particles of earthy 

 matter dissolved in it, and which are not easily deposited, un- 

 less at high water, when mud and earth become mixed with 

 them. 



