404 Expedition to the 



ny considered a product of pseudo-volcanic fires, said to exist 

 on that river. 



Of the extent of this formation of trap, and of the actual 

 elevation which it attains, we have no very definite informa- 

 tion. Some of the greenstone hills which we examined, ap- 

 peared to rise nearly to the region of perpetual frost. 



In the soils resting on the rocks of this formation, gra- 

 vel and water-worn pebbles rarely occur, except in situations 

 where it is easy to see they may have been derived from the 

 underlying sandstone. 



We are not disposed to enter into any discussion concern- 

 ing the origin of the trap rocks. The volcanists and those 

 who believe the trap formations to have been thrown up in 

 a state of fusion from beneath the crust of the earth, will 

 have a ready explanation of a fact mentioned in our journal, 

 namely, that pieces of charred wood were found inclosed 

 in the sandstone underlying the formation in question. 



Though we sought in vain for some evidence that the 

 rocks of this formation traversed the strata of sandstone in 

 the manner of the whin dikes of England, we are conscious 

 our examinations were too limited to justify us in asserting 

 that this is not the case, nor can we adduce a single fact, 

 from which it could be inferred, that these rocks have been 

 deposited, like the accompanying strata of sandstone, from 

 suspension in water. We saw no instance of their alternation 

 with the sandstones, and no appearance of the gradual 

 transition of these rocks into each other. The country oc- 

 cupied by this formation presents scenery of a very peculiar 

 and interesting character. It is remarked by Humboldt,* that 

 in the Canary islands, in the mountains of Auvergne, in the 

 Mittelgebirge in Bohemia, in Mexico, and on the banks of 

 the Ganges, and we may add, in the United States, the for- 

 mation of trap is indicated by a symmetrical disposition of 

 the mountains, by truncated cones, sometimes insulated, 

 sometimes grouped, and by elevated plains^ both extremities 

 ofxvhich are crowned by a conical rising. In some of the 

 unpublished drawings by Mr. Seymour, these peculiar fea- 

 tures of the scenery of the floetz trap formation have been 

 preserved. 



From the account we have given of these rocks, it will 

 be perceived, that here, as in Mansfeld. Thuringia, and the 

 circle of Saalet, the red sandstone, the porphyritic and 



* Personal Narrative, vol. i. p. 87. American Edition. 



f Annals of Pbilos. vol. xviii. p. 248, on the authority of Friesleben. 



