122 Scientific Intelligence. 
It is inclosed on the east and west - a line of bluffs of irregular 
—— and extremely irregular direction 
This plane, Dyer about 40,000 square miles, has been formed 
in sha course of ages a the material brought down from the uplands 
“by the Misciesippi and its tributaries. ‘The river has therefore raised 
oc the sea the soil which constitutes its own bed. It flows down this 
plane of its own creation, ina serpentine course, frequently crowding 
on the hills to the left, and once passing to the opposite side and wash- 
ing the base of te: blutf which makes its appearance on the west at 
the town of He 
The actual rhe from the mouth of the Ohio to the coast of the 
he is, in round numbers, as stat ed, 500 miles. The computed length 
of the Southwest Pass, is 1,178 miles; ee the average descent at high 
water ;%/5ths of a foot, or Bt i inches per mile. 
The — of the river is therefore Jenabinead out nearly seven 
hundred miles, or is more than doubled by the remarkable flexures of 
its channel ; and the rate of its descent is reduced by these flexures 10 
less than one-half the seg: of the plane down which it flows. 
the ‘summer and autumn, when the river is low and water js scant- 
from the banks he consequence is, that the borders of the rivers 
hich received the first and heaviest vi che are raised higher above 
the general level of the plane than the soil w re remote; a 
bd ? 
70 and 180 feet or more. The mean velocity of the Mississippi at ils 
