Notes on American Geology. - 245 
These same formations extend through Indiana and Illinois to the 
Mississippi river, with a gentle southwest inclination ; but as we 
ascend the Missouri, we find the strata rise with the ication of 
the land, or slightly dipping to the east. Thus the Mississippi 
flows in a grand depression formed by the rise of the Appalachian 
chain on the east, and-the Rocky Mountains on the west, a syn- 
clinal line, that for the enormous tract of country it occupies, and 
the vast extent of the two inclined planes of which it is the point 
of greatest depression, has no equal on the globe. To this fortu- 
nate geological feature of the country, we owe the gigantic scale 
of the rivers, sweeping thousands of miles through level and fer- 
tile regions, and offering to industry and enterprise sources of 
national wealth and prosperity, far surpassing wal in the records 
of history. 
The immense tract of country which lies between the Missis- 
sippi and the Rocky Mountains, owes its eastward inclination to 
the uplift of that chain, which has risen in the ‘secondary and ter- 
tiary eras to a much greater elevation than the Appalachian range, 
and consequently raising the cretaceous formations, which abound 
high up the Missouri, to a much higher level than they attain on 
the Atlantic coast. 'This was caused solely by the rise of the 
Rocky Mountains, and not assisted by a depression along the 
eastern coast, as Elie de Beaumont supposes, because the occur- 
rence of three tertiary deposits along that line proves, that so far 
from a depression having there taken place, the land has actually 
been upheaved, at the same time that the tertiary rose on the 
shore of the Pacific. This proves that the Appalachian and 
Rocky Mountain chains rose simultaneously to a certain degree 
in the upper tertiary era, and therefore it is not toa see-saw mo- 
tion of the earth’s crust that I would attribute the greater eleva- 
tion of the cretaceous strata towards the Rocky Mountains, but 
to a more rapid uplift of that chain than has taken place in the 
Appalachian range. The greatest elevation of the latter during 
the upper tertiary period seems to have been between two hun- 
dred and three hundred feet, and this only in the northern part 
of the United States, as in the middle and southern States, this 
newest tertiary, which gives the maximum of elevation we have 
stated, does not attain more than ten or fifteen feet above the 
level of the sea. On the coast of California, Mr. Nuttall found 
shells of recent species two hundred feet above the sea. These 
