Rocky Mountains. 391 



apparently not very recent, contains remains of marine ani- 

 mals and plants, and embraces some extensive beds of pud- 

 ding stone. It may be remarked, that the sand and gravel 

 composing these aggregates, have the same close resemblance 

 to the materials of the granitic mountains, as we have alrea- 

 dy observed in the uncemented materials of the plain. In- 

 deed, it does not seem easy to determine whether the sands, 

 gravel stones, and pebbles, now loosely strewed over the ex- 

 tensive plains of the Platte and Arkansa, have been brought 

 down immediatel) from the granitic mountains, whence they 

 were originally derived, or have resulted from the disinte- 

 gration of the stratified sandstones, and conglomerates de- 

 posited during a long series of ages, while the waters of the 

 ocean rested upon the great plain, and washed the base of 

 the Rocky Mountains. The wide and equal distribution of 

 these sands; in other words, the very gradual slope of the 

 debris of the mountains, would seem to countenance the lat- 

 ter supposition. 



The position of the strata of sandstone, varies in the dis- 

 tance of a few miles, from nearly horizontal to an inclination 

 of more than sixty degrees, and that without any very mani- 

 fest change of character, or the interposition of any other 

 stratum. 



The laminae most distant from the primitive, occupying 

 the eastern sides of the first ridges, though lowest in ac- 

 tual position, may with propriety be considered uppermost, 

 as resting on those beyond. At the level of the surface of 

 the great plain, they sink beneath the diluvial deposites,* and 

 in the neighbourhood of the river Platte, are no more seen. 

 The uppermost are of a yellowish gray colour, moderately 



* To the general covering of water-worn debris, derived from all the 

 strata, and now extending over a great part of the earth's surface, the 

 name Diluvium has been given, in allusion to that great and universal ca- 

 tastrophe to which its deposition has been supposed assignable. By this 

 name, it is intended to distinguish it from the partial debris occasioned by 

 causes still in operation, such as the slight wear produced by the present 

 rivers, the more violent action of torrents, <Scc. To the latter the name 

 Alluvium has been appropriated, but many authors who perhaps do not 

 confound the two classes of phenomena, have ambiguously applied the 

 word alluvial to both. In the earlier parts of this work, we have some- 

 times distinguished the diluvial formations as primary soils, which, as hav- 

 ing less of implicit allusion to a fallacious theory, may perhaps be thought 

 equally applicable. But, with the hope of being more easily understood, 

 we prefer to adopt such words as have been used by good authorities. For 

 further information concerning the use of the above words, see Conybeare 

 and Phillips' Geology of England and Wales, Part I. p. 28. 



