338 
POOR ON MAP OF THE UNITED STATES [June 14, 1858. 
from each other. The western portion of the continent delineated, 
is occupied by several mountain ranges rising from an immense 
plateau, extending nearly one third of the way across the continent 
from east to west. On some parts of this plateau, the width of these 
mountain ranges is nearly 1000 miles. The great plateau on which 
they stand begins to rise from the Mississippi and Missouri Rivers. 
At first the ascent is gradual, but after going west about 500 miles 
from the valley of the Mississippi River, the rate of ascent of that 
portion of it drained by the Red Arkansas, Platte, Kanzas, and Niobra- 
hah, increases to about 8 feet to the mile, till an elevation is reached 
of from 7000 to 8000 feet above the sea. The western slope of this 
plateau, and of the mountains which crown it, is, on the other hand, 
very abrupt — the mountains rising in some cases to an altitude of 
13,000 feet in a distance of 100 or 150 miles from the Pacific coast. 
Between the summits of the Rocky Mountains on the eastern slope 
of the plateau, and the Sierra Nevada lying on the western, is an 
immense elevated, arid, and desert plain, having an independent 
system of lakes (salt), and rivers, similar to the systems of the 
Dead and Caspian Seas. 
The easterly slopes of the plateau of the Rocky Mountains par- 
take largely of the character of the plateau itself, being arid and 
sterile, till the meridian of 99 or 100 west from Greenwich is 
reached. In the United States, with the exception of the head 
waters of the Missouri, only a small, if any portion of the territory 
between the meridians named, and the summits of the Sierra 
Nevada, can be cultivated without irrigation; a fact which is 
only imperfectly understood even by the people of the United 
States. After the Sierra Nevada is crossed, there is a narrow belt of 
fertile and well watered country occupied by the states of Cali- 
fornia and Oregon and the territory of Washington. 
The next grand division shown on the map is that occupied by 
the Mississippi River. This presents features entirely dissimilar 
to the division just described. It is characterised by the uni- 
formity of the surfaces and inclinations of its great plains, their 
slight elevation above the sea-level, and the fertility of their soil. 
The surface of the Mississippi River at the mouth of the Ohio, 1200 
miles from the Gulf of Mexico, is only 275 feet above the level of 
the sea. Above the mouth of the Ohio, the rate of fall is more 
rapid, yet still very uniform. At the mouth of the Minesota River, 
2192 miles from the Gulf, the elevation of the Mississippi is only 
744 feet above tide. The rate of fall from this point to the sea 
is about 4 inches to the mile. The Mississippi River, though 
much inferior to the Missouri in length, and in the area of the 
