526 Geology, §c. of Tennessee, -§-c. 
ging. In the vicinity of the town, there is a curious exhibition » 
of the fact. A stream of water has worn away the earth to 
the depth of fifteen or twenty feet, and is continually length- 
ening the chasm, in the direction opposite to its own course. 
Thus, as the water flows from the town, the chasm approaches 
it. In examining the cause of this fact, I perceived it was 
owing chiefly to the difference of cohesion in the alluvial de- 
posits, of which the earth is formed. That at the surface, 
being a thick loam, wears away with more difficulty than the 
deposit below it, which consists of a loose sand. ‘The conse- 
quence is, that the water, which has once obtained a perpen- 
dicular passage of a few inches through the first, washes away 
the second with such rapidity, that it is constantly undermining 
it. ‘This occasions a perpetual caving in of the surface, ina 
direction opposite to the course of the stream. The same fact 
is observed in many parts.of the country fora great distance 
above Natchez. If there be wanting any other fact to prove 
that the earth on which the town of Natchez stands, is alluvial, 
it is found in the effect which the Mississippi has upon the base 
of the Natchez bluff. In consequence of a bend in the river, 
the whole force of its current is thrown against this base. if 
it consisted of solid rock, the river would probably have no 
effect upon it; but of such loose and friable materials is it com- 
posed, that the river is continually undermining it, and produ- 
cing effects not less to be dreaded than those of an earthquake. 
Several years ago, a great number of acres sunk fifty feet or 
more below the general surface of the hill: and in 1805, there 
was another caving of that part directly over the small village 
at the landing. Several houses were buried in consequence 
» 
features of the country. But I have two facts, of a geological 
kind, to mention, both of which go to confirm the opinion. 
