Notes on American Geology. 245 



These same formations extend through Indiana and lUinois to the 

 Mississippi river, with a gentle southwest incHnation ; but as we 

 ascend the Missouri, we find the strata rise with the elevation 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 any 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 uphft 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 hne 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 to a 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 



