30 SUEVEY OF COLORADO AND NEW MEXICO. 



18. Sandstone, dip. 11°. This sandstone lias a reddish tinge, and is 

 less massive than 14. 



17. Drab clay. ) 



16. Coal, (No. 4.) > 20 feet, obscnre. 



15. Drab clay. ) 



14. Sandstone, massive, 60 feet. 



13. Drab clay. 



12. Sandstone. 



11. Drab clay. 



10. Coal, (No. 3.) 

 9. Drab clay. 

 8. Sandstone, 25 feet. 

 7. Drab clay. 

 6. Coal, (No. 2,) 8 feet. 

 5. Drab clay. 



4. Sandstone, about 25 feet. 

 3. Drab, lire clay, 4 feet. 

 2. Coal, (No. 1,) 11 to 14 feet. 

 1. Sandstone. 



In bed No. 23 there are three layers of sandstone, which contain a 

 great variety of impressions of leaves. Below coal bed No. 6 there is a 

 bed of drab clay, seven feet thick, with a coal seam at the outcrop, three 

 feet thick ; but the coal appears to give out or pass into clay as the bank 

 is entered, so that there are ten feet of clay above coal bed No. 6. 



Much of the iron ore is full of impressions of leaves in fragments, stems, 

 grass, &c. The ore is mostly concretionary, but sometimes it is so 

 continuous as to give the idea of a permanent bed. There are several 

 varieties of the ore of greater or less purity. Above coal bed (5) there 

 is a seam of iron, with oyster shells, apparently Ostrea suhtrigonaUs. 

 or the same si)ecies found so abundantly near Brown and O'Bryan's 

 coal mine, about twenty miles southeast of Cheyenne. Nearly a dozen 

 openings have been made here for the coal. 



These coal beds are the more valuable, and can be more easily wrought 

 than any in Colorado. The great thickness of the coal strata has been so 

 uplifted, and the surface worn away, that the beds are all eaeily accessible, 

 and one can walk across the upturned edges of irom 1,200 to 1,500 feet in 

 thickness and then they incline eastward, and die out in the plain. liliulit 

 somewhat difficult to give a satisfactory reason why they have not been 

 swept away or concealed by debris, as they have been iu most other locali- 

 ties. Leaning against the sides of the mountain s between South Boulder 

 canon and that of the maiuBoulder Creek, areimmense walls of sandstone, 

 possibly paleozoic or the lower beds of the trias, partially metamorphosed 

 by heat. These walls rise to the height of 1,500 to 4,000 feet above the 

 valley, and thus seem to have protected these formations from the erosive 

 action, which, according to the position that I have taken in this report, 

 is local, and must have come directly from the mountains. 



A beautiful valley has been scooped out by the South Boulder, leav- 

 ing a bench covered with debris between the two Boulder Creeks. 

 Before reaching these huge sandstone walls, we pass over a portion of 

 the cretaceous, and a great thickness of the red beds, inclining at a high 

 angle. 



Immediately south of i^[iQ South Boulder Creek there is a high bench 

 that extends up close to the base of the mountains, and is covered with 

 drift and boulders, three miles in width, entirely concealing all the un- 

 changed rocks. But in the valley of Coal Creek, seven beds of coal are 

 revealed by the scooping out of this valley. These beds all incline at a 



