Rocky Mountains. 401 



conclusion appears to be justified, that this rock extends from 

 near the Arkansa on the north, to a point beyond Red river 

 on the south, and from near the mouth of the Canadian, 

 an unknown distance to the west. It is not unlikely, it may 

 exist about the sources and upper branches of the Rio Co- 

 lorado ot California, the Red river of Santa Fe, and the 

 other J^ed rivers of New Mexico. Near the mountains, and 

 for a great distance to the south and east of the High Peak, 

 it is covered by the gray sandstone. 



Other secondary rocks found in different parts of the great 

 valley of the Mississippi, will be noticed hereafter. Those 

 above enumerated, seem to have a peculiar dependence upon 

 the Rocky Mountains, and for this reason, we thought pro- 

 per to consider them in connection with that range. They also 

 appear in some measure independent of the other members 

 of that great secondary formation, on the borders of which 

 they occur. 



The peculiar features of the region occupied by these 

 rocks, have been minutely described in the narrative of our 

 journey. It is a region destined by the barrenness of its soil, 

 the inhospitable character of its climate, and by other phy- 

 sical disadvantages, to be the abode of perpetual desolation. 

 The immense grassy plains on its southern and eastern bor- 

 ders, are adapted to the feeding of cattle and sheep, and it is 

 not improbable, the countless herds of bisons and wild horses, 

 will soon give place there, to domesticated animals. The 

 coal, salt, plaister, and iron, which constitute the mineral 

 wealth of this portion of the United States' territory, lose 

 much of th»:ir value, on account of their remoteness from 

 navigable streams. Beautiful carnelians and agates occur in 

 the alluvial regions of the Platte and Missouri, but these 

 will never become objects of any importance. 



III. — Floetz Trap Rocks, 



Another family of rocks of recent formation, and connect- 

 ed with the sandstone last mentioned, remains to be noticed. 



These are rocks of basaltic conformation, belonging to the 

 class by some mineralogists denominated superincumbent, 

 and by many considered of volcanic origin. They present 

 a striking contrast by their dark colour, and by the vastness 

 and irregularity of their masses, to the smooth, light, and fis- 

 sile sandstones on which they rest. Sometimes they are com- 

 pact, and apparently homogeneous in their composition, 

 in many particulars of structure, form, hardness, &c. seem- 

 ing more analogous to the primitive rocks than to those re- 



VOL. II. 51 



