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From the mouth of the Platte river the forests are narrower. The prin- 

 cipal trees are the American and red elm, the soft maple, Canadian poplar, 

 white and red ash ; the most common undergrowth, horse-briar, fox and 

 false grapes, red root, gray dogwood, currant, and gooseberry, with shrubs 

 and dc3nse rushes along the banks of the river. The same trees and shrubs 

 grow on the numerous islands, that are generally bordered with black and 

 long-leaved willows. In the higher situations, and at the head of creeks, 

 we meet vviili the black walnut and mulberry, bass-wood, nettle-wood, in- 

 termingled with the common hawthorn, prickly ash, «fcc. On the high 

 grassy or rocky banks, the black and bar oaks consiitute the principal 

 growth, but occasionally intermixed with the wild cherry, red cedar, horn- 

 bean, wild roses, and sumach. The low prairies bordermg the rivers have 

 a deep, fertile soil, and abound with sedge grasses and leguminous plants. 

 Finally, taking a pictorial view of the country, the verdure of its hills and 

 prairies affords a pleasing contrast with the naked sandbars in the rivers. 



I have been thus particular in describing the vegetation of this part of 

 the country, not only as a feature in its physical geography, but as a point 

 of comparison with the more northerly regions which 1 have yet to de- 

 scribe. For the same reason, I shall now proceed to lay down the most 

 prominent traits of its geology. 



The predominant rock in this region of country to which I am now re- 

 ferring — namely, from the Platte river to Council Bluffs — is the carbonif- 

 erous or mountain limestone, well characterized by its fossils, consisting 

 principally of the joro<:/Mc/a/o6a^a, producta ■punctata^ orihis, deUh?jris, tur- 

 binolia fungites, crinoldal remains^ <fec.; most of these genera affording 

 several new species as yet undescribed. 



This formation is a continuation of that which underlies so vast ah ex- 

 tent of the Mississippi valley, but having a much larger development over 

 the States that are to the east of this river, and extending even to the Al- 

 leghanies. It is the support of important coal-basins, and rests upon a 

 group of Silurian rocks, beginning at the falls of St. Anthony, extending 

 Itself from north to south, constituting the mineral regions of Iowa, the 

 Wisconsin, and the Missouri, and losing itself somewhere in the State of 

 Arkansas. This last-mentioned group is bounded at the north by amphi- 

 bolic rocks, steaschists, and clay slates, that extend to beyond 47° of N. 

 latitude ; and at the south, also, by steaschists and clay slates, that compose 

 the principal rocks at Little Rock in the State of Arkansas ; and also those 

 ot the Washita mountains. These rocks are referrible to certain members 

 of the group to which Mr. D'Homaluis d'Halloy has given the name o[ ter- 

 rain ardoisier, and have their equivalent in the series of iha grauivacke 

 of German geologists. Thus, by this distribution of the geological forma- 

 tions, it would seem that, more particularly to the west of the Mississippi, 

 the Silurian group is imbedded within the "terrain ardoisier," or grau- 

 wacke, just as the carboniferous series, with its coal measures, overlies the 

 Silurian. 



From what 1 have so far said of the geology of the west, it will be 

 perceived that I have adopted the classification of the older tbssiliferous 

 rocks, as laid down by its illustrious author, Mr. Murchison. But I 

 must confess that I hesitated about it a long time; notwithstanding the 

 opinions of my friends MM. Vanuxem and Conrad, both distinguished 

 geologists and conchologists, who had recognised among my fossils irre- 



