THE MISSISSIPPI VALLEY. 27 



As already explained, the foregoing table exhibits the daily height of the 

 water on the bar at Wheehng for the year 1848; and at the foot of each 

 column is shown the number of cubic feet discharged by the Ohio during the 

 month to which the depths in that column apply, and also the uniform height 

 at which the water could have been maintained by the discharge of the month, 

 if that discharge had been uniform. 



On summing up these result, we find that the total volume discharged by the 

 Ohio at Wheeling, for the year 1848, was — 



822,719,000,000 cubic feet. 



Dividing this quantity by 366, we obtain for the average daily discharge for 

 that year — 



2,248,000,000 cubic feet. 



If we now refer to Table IV, or to the formula from which that table was 

 constructed, we shall find that the daily average quantity discharged during the 

 year was just sufficient to have maintained the water upon the Wheeling bar at 

 an uniform height of 8j%% feet. 



The area drained by the Ohio and its tributaries, above Wheeling, is estimated 

 in this paper at 24,337 square miles ; or, 



678,476,COO,000 square feet. 



It follows, then, if we divide the above annual discharge in cubic feet by the 

 area drained, that the volume of water which flowed down the Ohio, at Wheel- 

 ing, in 1848, was just sufficient, if spread over this space, to have raised the sur- 

 face ItVo'o feet-, or, 



14tWo inches 



Such is the value of the total drainage of the region watered by the upper 

 Ohio for that year. The greatest monthly value was in December, when it 

 amounted to — 



"2^%%- inches ; 



and the least monthly result was in September, when it amounted only to — 



TcVij of an inch. 



There is one other fact exhibited in Table V, which has a most important 

 practical application, and may be properly noticed in this connexion. 



It appears by the record that the water was below five feet in February, and 

 also in April and May ; that it was down nearly to three feet in June, as low as 

 four feet in July, at three and a half feet in August, below two feet in Septem- 

 ber, two feet and two inches in October, and again at four and a half feet in 

 November ; and yet the calculation shows that the discharge was sufficient, in 

 each of those months, excepting only September and October, to have main- 

 tained the navigation at five and a half feet, or more, throughout the month. 



