NARRATIVE OF THE EXPEDITION. 245 



The length of the Mississippi, from the Gulf of Mexico, pur- \ 

 suing its involutions, may be stated to be three thousand miles. 

 By estimates from the best sources made, respectively, during 

 the expeditions of 1820 and 1832, it is shown to have a wdnding 

 thread of three thousand one hundred and sixty miles. Taking 

 the barometrical height of Itasca Lake at fifteen hundred and 

 seventy-five feet, it has a mean descent of a fraction over six 

 inches per mile. As one of the most striking epochs in Ame- 

 rican geography, we have known this river, computing from the 

 era of Marquette's discovery to the present day (July 13, 1832), but 

 one hundred and fifty -nine years — a short period, indeed ! How 

 rich a portion of the geology of the globe lies buried in the flora 

 and fauna of the tertiary, the middle or secondary, and the palseo- 

 zoic eras of its valley, we have hardly begun to inquire. It will, 

 doubtless, and, so far as we know, does, contribute evidences to the 

 antiquity and mutations of the earth's surface, conformably to the 

 progress of discoveries in other parts of the globe. The immense 

 basins of coal, found in the middle and lower parts of its valley, 

 prove the same gigantic epoch of its flora which has been esta- 

 blished for the coal measures of Europe,* and sweep to the winds 

 the jejune theory that the continent arose from a chaotic state, at 

 a period a whit less remote than the other quarters of the globe. 

 "While the large bones of its later eras, found imbedded in its 

 unconsolidated strata, prove how large a portion of its fauna were 

 involved in the gigantic and monster-period. 



* Entii-e trees are often found imbedded in its rocks of the middle era, as is evi- 

 denced by an individual of the juglans nigra, of at least fifty feet long, in the River 

 De Plain e, valley of the Illinois, Vide Appendix. 



