38 PHYSICAL GEOGRAPHY OF 



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



Ijs inches : 

 and the least monthly drainage in August, when it was but — 



imS of an inch. 



In every month of the year 1845, from April to December, including both, 

 one or two periods of low water occurred, requiring the aid of the artificial 

 supply. Indeed, throughout the whole space of eleven years, which the authen- 

 tic records cover, there is found no year in which the navigation of the Ohio 

 was more precarious than in the year 1845, when it was subject to frequent and 

 total interruptions, both from ice and low water. 



To have maintained a depth of 5 feet in the channel throughout that year, the 

 reservoirs would have been drawn upon twelve times, and would have been filled 

 again eleven of those times by the surplus which was wasted during the same 

 month. Even in this year, small as was the quantity which the tributaries fur- 

 nished, and frequent as were the periods of deficiency, the greatest volume 

 needed to be accumulated in the reservoirs at any time, was but 28,744,000,000 

 cubic feet. In the months of July, August, and September, there was a period 

 of 79 consecutive days, when the depth on the Wheeling bar was less than 5 

 feet ; yet the deficiency for all that period was less than 29,000,000,000 cubic 

 feet — a volume no larger than can be collected in three or four reservoirs, which, 

 on almost any part of the Monongahela or Alleghany, could be formed by dams 

 from 35 to 40 feet high. 



Yet, as all the objections that can possibly be urged against the construction 

 of high dams on these great rivers may be obviated, as already stated, by resort- 

 ing to the smaller afliuents, it will be the aim of the writer to make a first 

 demonstration of his plan in localities remote from the leading channels of trade, 

 and where there are no important private interests to be consulted. 



The only natural lake that would be at all available for this object is the Cha- 

 tauque, of which the waters flow into the Alleghany, above Warren. But this 

 beautiful basin is itself filled from an area of country too small to contribute any 

 material supply for the purposes here contemplated, and cannot, therefore, be 

 resorted to with profit. 



