532 
REVOLUTIONS IN AMERICAN HYDROGRAPHY. 
of its fish, and perhaps be not wholly without sensible influ¬ 
ence on the water of the Black Sea. 
Improvements in North American Hydrography . 
We are not yet well enough acquainted with the geography 
of Central Africa, or of the interior of South America, to con¬ 
jecture what hydrographical revolutions might there be 
wrought; but from the fact that many important rivers in 
both continents drain extensive table lands, of very moderate 
inclination, there is reason to suppose that important changes 
in the course of rivers might be accomplished. Our knowl¬ 
edge of the drainage of North America is much more com¬ 
plete, and it is certain that there are numerous points where 
the courses of great rivers, or the discharge of considerable 
lakes, might be completely diverted, or at least partially di¬ 
rected into different channels. 
The surface of Lake Erie is 565 feet above that of the Hud¬ 
son at Albany, and it is so near the level of the great plain 
lying east of it, that it was found practicable to supply the 
western section of the canal, which unites it with the Hudson, 
with water from the lake, or rather from the Niagara, which 
flows out of it. Hence a channel might be constructed, which 
would draw off into the valley of the Genesee any desirable 
proportion of the water naturally discharged by the Niagara. 
The greatest depth of water yet sounded in Lake Erie is but 
two hundred and seventy feet, the mean depth one hundred 
and twenty. Open canals parallel with the Niagara, or di¬ 
rectly toward the Genesee, might be executed upon a scale 
which would exercise an important influence on the drainage 
of the lake, if there were any adequate motive for such an un¬ 
dertaking. Still easier would it be to create additional outlets 
for the waters of Lake Superior at the Saut St. Mary—where 
the river which drains the lake descends twenty-two feet in a 
single mile—and thus produce incalculable effect, both upon 
that lake and the great chain of inland waters which commu¬ 
nicate with it. 
The summit level between Lake Michigan and the Dos 
