42 PHYSICAL GEOGRAPHY OF 



It appears from the foregoing record that the vohime of water which flowed 

 down the Ohio at Wheehng, in 1843, amounted to — 



961,382,000,000 cubic feet; 



and that the equivalent average daily supply is — 



2,634,000,000 cubic feet. 



This quantity is sufficient to maintain an uniform height throughout the year, 

 upon the Wheeling bar, of — 



OjVij feet. 



The total drainage for that year was IrVA feet, or — 



17 inches. 



The greatest monthly drainage was in April, when it amounted to — 



4rVo inches ; 



and the least monthly drainage in August, when it amounted only to — 



t'tnj of an inch. 



If we look over the values of the monthly drainage for the six years which 

 have been analyzed, it will be observed that the volume of water which passed 

 down the Ohio in April, 1843, was greater than the amount shed during any 

 other month in all that period ; while the amount discharged in August, 1843, 

 was less than the discharge of any other month in the same space of six years. 



The results of this year's analysis show, also, that the navigation might have 

 been very easily maintained at a height of more than 5 feet, by two or three 

 reservoirs of very moderate capacity. 



It is not necessary to multiply observations bearing on a fact already suffi- 

 ciently explained. The capability of the upper branches of the Ohio to furnish 

 adequate reservoir sites will be alluded to in the sequel. It is sufficient to say 

 here, that the navigation may be permanently upheld, free from all obstruction 

 from ice or drought, by the construction of a few dams across its tributary 

 streams, and providing those dams with locks for the convenience of the local 

 trade, and appropriate pipes and valves for drawing off the water held in reserve, 

 as it is needed. 



The same dams that will serve to supply the channel with water in the sum- 

 mer months, and sweep away the ice which collects during the low water of 

 winter, will enable us also to shut off the water entirely, so as to lay bare the 

 bars when it is desirable to do so, to remove obstructions, and, as we shall pre- 

 sently see, even to hold back the floods, when they threaten to desolate the val- 

 ley below. In fact, we can exercise as complete control over this great river as 

 we possess over the discharge of a hydrant. 



