824 LE. W. Hilgard on the Quaternary of Mississippi. 
bottom, there being a sudden ascent of from three to as much as 
ten or more feet, while by a more gradual slope, thereafter, the 
difference of level often amounts to twenty feet and more. In 
the second place, not only is there almost always a decided differ- 
ence between the materials, and consequently the soils and natu- 
ral vegetation, of the first and second bottoms of one and the 
same stream (for example, § 809), but the nature of the latter 
soil shows a certain correspondence all over the state, so as to 
be mostly recognizable at a glance by an experienced eye. It 
is only in the lower portion of the course of the larger streams, 
that this distinction is lost in a great degree. 
The soils and subsoils referred to are mostly pale gray or buff- 
colored, fine siliceous silts, with but little coarse sand, accompa- 
dering uplands, whereas the first bottom soils are chiefly depend- 
ent, for their character, upon the materials into which the bed of 
viz., that the Bottom praine contains the fossils of the 
umm 
as known, present but a very few and indistinct stems and leaves, 
occasionally, in the more clayey bands. But it must f 
ered, that neither is the Bluff formation itself represented on the 
Streams in question. It therefore remains to be determined 
whether those fossils are an essential characteristic of the Bottom 
prairie, outside of the region of the Bluff formation, and on the 
sma re i disooyaHne 
on th 
territory of the Bluff formation. And as to the existence of 
any representative of that epoch in the great Mississippi Bottom 
itself, I have not had any opportunity of observing. 
It is evidently during the period of the Second Bottoms that 
the great denudations which have traced the valleys of our water- 
courses of the second, third, and even fourth order, were accom 
