PRELIMINARY REMARKS. 
33 
and winds keeps a perpetual flow from the mountain to the sea; 
and the wind current, in passing over the ocean, loads itself 
with vapor, which is ready to fall in mist and rain upon sur¬ 
faces cooler than itself. 
In these simple facts we find an explanation of the origin of 
the river systems of this country, and of all countries. The 
Appalachian, the Rocky Mountain, and Pacific Coast chains, 
with their numerous spurs and branches stretching from the 
Gulf to the British possessions, form an immense condensing 
surface, sufficient to irrigate and fertilize 3,000,000 of square 
miles. It is a singular fact, that the United States is watered 
by rivers which rise in its own borders. The crest of the great 
water shed dividing the river systems which flow to the north 
and south, formed by the Lawrentine chain, rises not far from 
the boundary between the British and American territories. 
The rivers of the Atlantic slope are short, and comparatively 
small. The Potomac, the Delaware, and Susquehannah spread 
out into wide and deep bays. This results from the porous 
nature of the tertiary deposits which belt the coast. The Hud¬ 
son and other northern rivers are rock-bound, and hence their 
bays are narrow and inconsiderable. The tide flows up the 
Hudson 160 miles from the ocean. It cuts the primitive rocks 
of the Highlands and some of its branches, and flows over the 
lower silurian formation beyond. 
The Mississippian is the great river system of the United 
States. It is second only to the Amazonian. The Missouri is 
the great trunk of this system. It rises high up in the Rocky 
Mountain chain. The innumerable streams draining the eastern 
slope, converge and form four great rivers, which, uniting in the 
distant plain, form the Missouri. This unites with the Missis¬ 
sippi twenty-five miles above St. Louis. Measuring its wind¬ 
ings, it has already reached a point 1500 miles from its source, 
and its journey is only half finished. Its current is rapid, and 
it carries mud and sand, derived from the soft cretaceous and 
tertiary formation through which it has flowed. A particle of 
water, starting from the steep sides of the Rocky mountains, 
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