30 PHYSICAL GEOGRAPHY OF 



By referring to the foregoing record of heights for the year 1847, we obtain 

 the following valuable results : 



The total drainage of the Ohio at Wheeling was — 



1,142,258,000,000 cubic feet; 



and the average daily discharge — 



3,129,000,000 cubic feet. 



From which it results, by applying the formula, or Table IV, that if the water 

 had all been shed uniformly, so as to maintain the river throughout the year at a 

 constant height, that height would have been lOyV feet upon the Wheeling bar, 

 or within a small fraction of two feet more than in the year 1848. 



If we again divide the area drained into the volume discharged, we obtain for 

 the year 1847 a total drainage equal to lAVo feet ; or, 



20i inches. 



The greatest drainage of this year, also, was in the month of December, 

 when it amounted to — 



3/oV inches ; 



and the least monthly drainage again in September, when it amounted to — 



i%% of an inch. 



It appears, therefore, that the total drainage of the upper Ohio, in 1847, was 

 about 38 per cent, greater than that of 1848 ; that the greatest monthly drain- 

 age of that year was 35 per cent, greater than that of 1848 ; and the least 

 monthly drainage nearly 100 per cent, greater than the least monthly drainage 

 of 1848. 



On comparing the two tables further, we find that the irregularities were very 

 great. In the month of October, 1847, the river discharged more than eight 

 times as much water as in the same month of 1848 ; while the discharge for a 

 single day — the 15th of December, 1847 — was as great as that of sixty days in 

 September and October, 1848. 



The computation of the daily and monthly drainage of this year also leads to 

 some very valuable practical observations. 



In 1848 the height of the water at Wheeling frequently oscillated between 

 22 and 27 inches through September and October ; although in those two 

 months the actual discharge was sufficient to have maintained the navigation 

 constantly at a depth of 3yVo feet — a depth sufficient for the movement of a 

 respectable class of freight boats, and consequently to protect the public 

 against prohibitory or extravagant charges. All that was that year (1848) neces- 

 sary to prevent this irregularity, was two small dams — one on each river above 

 Pittsburg — to act as regulators of the natural flow. Two dams of very mode- 

 rate height, and two men to control them — dams which would also have fur- 

 nished a sufficient additional supply of water to raise the depth, even in those 



