400 Expedition to the 



and of the Llanos of Caraccas, resting on the granite of the 

 Oroonoko,* in South America, also to that spoken of by 

 Mr. Burkhardt, at the entrance oi Nubia, super) mposrd up- 

 on the granite of S\ene, lo thai of Aberdeenshire in Scot- 

 land,! to that of Haldon hill, overlaying the granite of Dart- 

 moor in England,:)^ to that mentioned by Mr. Schookrafi.^ 

 as found near Lake Superior, and probablv to that of Beh- 

 ring's4sland off the coast of Kamschatska,|| but it does not ap- 

 pear that those formations have the same peculiarities in re- 

 gard to inclination. 



If this formation of sandstone consisting of the two varie- 

 ties just mentioned, ev'='r extended across the valley of the 

 Mississippi to the Alleghany mountains, as some might be 

 disposed to believe, we cannot pretend to determine what 

 was its position, relative to the immense masses of floetz, 

 limestone, and other rocks now found in that valley. But as 

 the red variety is still extensively disseminated and usually 

 accompanied by those valuable substances salt and plaister, 

 it may not be amiss, to trace as far as our examinations have 

 enabled us to do it, the outline of the region which it occu- 

 pies. As we have before mentioned, it is found in the vici- 

 nity of the river Platte, in an highly inclined position, cover- 

 ing a narrow margin, immediately at the foot of the Rocky 

 Mountains. From the accounts of Lewis and Clark, w^ are 

 induced to believe, that it exists under similar circumstances 

 near the f.ills of the Missouri. On the Canadian, it is con- 

 stantly met with from the sources of that river, on the bor- 

 ders of New Mexico, near Santa Fe, in 105" west, until you 

 arrive within a short distance of its confluence with the Ar- 

 kansa, in longitude 97° west. The waters of the Canadian, 

 from flowing over the sandstone in question, acquire an in- 

 tense red colour, and are so impregnated with muriate of 

 soda and other soluble salts, as to be unfit for use. I'his we 

 are credibly informed, is also the case with the waters of a num- 

 ber of rivers tributary to the Arkansa, above the Canadian on 

 the same side, also with the waters of Red river. Hence the 



* See Humb. Pers. Nar. vol. 4, p. 384 and 572, also vol. v, p. 633, 

 Lond. Ed. 



t Mac Culloch in the Journal of Science and the Arts, vol. x, p. 30. 



\ Conybeare and Phillipps. Part 1, p. 132. 



^ Schoolcraft's Narrative, page 159. 



II Behrin^'s Island, says Pennant, consists of hig^h granitic mountains, 

 craggy with rocks and peaks, changing into freestone towardb the pro- 

 montories. Arct. Zool. vol. i, p. 219. 



