10 
AMERICAN GEOLOGY. 
Charles Ellet, he proposes to put in execution an analogous 
plan, to distribute the waters of the Ohio in a more equable 
manner by means of reservoirs, so as to preserve a given quan¬ 
tity on its bar at Wheeling. It must be noted, that in the 
execution of all similar projects certain geological results will 
follow. The detritus will be arrested in artificial basins; the 
stream, in its onward course, will be freed in part from sedi¬ 
ment; the accumulations which have been collecting at the 
mouths of rivers and in shallow ground, will be diminished in 
quantity, and their nature somewhat changed. The changes 
which improvements in navigation by dams, by diversion of 
streams by canals, are and quite important. These changes are 
not confined to the sediments. Certain species of fish become 
more widely distributed by means of channels of communication 
being opened between the lakes in the interior of the country 
and its coasts. The proteus of lake Erie has found its way to 
the Hudson river by the Erie canal, and the different species of 
limneas and unios now occupy its bed throughout its whole 
extent. 
§ 8. Notwithstanding the great extent of land, the North 
American continent is well watered. This is especially true of 
the United States. Situated between two oceans, it has a 
breadth of 2500 miles of land. The great western lakes are 
inconsiderable areas compared with the wide interval between 
the oceans. From the gulf of Mexico to the great lakes, 
or country of lakes, it is 1200 miles by the shorter route. 
Notwithstanding the great area of unbroken soil, the distribu¬ 
tion of the forces which supply water to 2,500,000 square miles 
is such, that the whole country can be traversed and cultivated. 
It is true that at the base of the Rocky mountains there is an arid 
country—one too dry to be inhabited. The westerly winds 
which are known to prevail in this country, are deprived of a 
large proportion of their water by the ranges intervening 
between this dry country and the Pacific ocean. 
Taking the whole globe into view, we may learn by an 
inspection of its map, that land and water are unequally dis- 
