360 CHANGES WROUGHT SINCE 



its rugged banks by that agent. It will be equally evi- 

 dent that the work is by no means suspended ; but that 

 the wear and tear is incessantly going on. 



B. F. Stickney, Esq. has written some valuable geo- 

 logical observations on the middle lakes or seas of North 

 America. He states that the elevation of the land be- 

 tween Michigan and the Mississippi levels does not ex- 

 ceed eighteen feet; and that boats pass, three or four 

 months of the year, without difficulty. This ingenious 

 inquirer asks, whether a dam, twenty or more feet high, 

 across the strait of Niagara, would not raise the middle 

 lakes high enough to discharge by the southwest toward 

 the gulf of Mexico? It violates no probability to sup- 

 pose it formerly was so. 



The falls of the Ohio near Louisville and the Rapids, 

 and its numerous and tributary rivers and streams from 

 Pennsylvania, Virginia, Ohio State, Kentucky, Illinois 

 and Indiana, all hurrying down their slopes with increas- 

 ed velocity and force, and producing constant changes 

 by their alterations, torrents, and floods. 



And lastly, I enumerate in this place the falls of St. 

 Anthony in the Mississippi, as situated within the limits 

 circumscribed by the great dam or barrier already 

 traced. 



Besides these traits of our country's character, by the 

 evacuation of the great inland sea, by the formation of 

 alluvions at the several openings and places of rupture, 

 by the production of rivers within the region anciently 

 occupied by that sea, and by the appearance in the un- 

 covered rocks of marine productions in almost every 

 part of the tract ; there is another class of phenomena* 



