250 



from denudation by a remarkable layer of calcareous septaria from 3 ta 

 6 feet in diameter, which afford splendid crystallizations of calcite and 

 numerous fragments of a large species of BacuUte. The largest frag- 

 ment that I saw was a foot in length, and fully 4 inches in diameter, 

 showing the corrugated divisions of the chambers through its entire 

 length. 



The oil-springs are about 200 feet above the base of Ko. 4. They now 

 yield about 3,000 gallons a year, which, by a rude process of distillation 

 on the spot, affords 55 per cent, of illuminating-oil and 15 per cent, of 

 benzine. An effort has been made to find oil by a deep boring, which, 

 at the depth of about 200 feet, ended in crumbling red sand, doubtless 

 No. 3. The nature of the strata in which these oil-wells are situated, 

 with what we now know of the underlying rocks, does not afford any 

 very favorable prospect of a large supply of oil from this locality. 



I made a somewhat careful examination of these Tertiary strata along 

 their outcropping edges for seven miles, and two sections across their 

 thickness, up the ravines of Oak Creek and Coal Creek, and am able to 

 present the following section, in which most of the thicknesses were 

 measured, though a few of the larger bodies of rock on Upper Oak Creek 

 were estimated. The portion examined was in township 19 south, range 

 69 west, and township 19 south, range 70 west, of sixth meridian, Fre- 

 om t County. 



Descending section. 



Ft. lu. 



31. Sandstones and shales • - - 



30. Coal G, left bank Upper Oak Creek 4 6 



29. Shale and sandstone, Upper Oak Creek (estimated) 100 



28. Coal F, right bank Upper Oak Creek 1 6 



27. Drab sandstone, Upper Oak Creek (estimated) 200 



26. Black and drab shales, Upper Oak Creek (estimated) 200 



25. Yellow sandstone. Oak Creek 10 



24. Sandstone, Upper Coal Creek (estimate) 30 



23. Shale, Upper Coal Creek . : 10 



22. Coal E, Upper Coal Creek = 1 4 



21. Brown shale, partly covered, Coal Creek 6 



20. Sandstone, Coal Creek 20 



19. Shale, Coal Creek 9 



18. Coal D, Coal Creek 3 6 



17. Dark shale. Coal Creek 7 



16. Coal C, Coal Creek 2 



15. Black and drab shale, with Coal B',1 foot 8 inches, Coal Creek. 40 



14. White sandstone, Coal Creek 4 



13. Drab shale, Coal Creek 2 



12. Drab sandstone, Coal Creek , 25 



11. Dark shales, with two coal-seams, each 1 foot, Coal Creek.. 40 



10. Sandstone (thickness estimated). Coal Creek 80 



9. Shale, with coal-seam 1 foot thick. Coal Creek « 25 



8. Coal B, worked by Denver and Eio Grande Eailroad Com- 

 pany, Coal Creek 6 



7. Fire-clay, Coal Creek , 1 6 



6. Coal A', Coal Creek 1 8 



5. Fire-clav, Coal Creek. 8 



4. Sandstone, etc. (thickness from E. X. Clark, M. E.) 80 



3. Coal A, Macomber's Gulch . . '4 6 



2. Adobe clay, thickness from E. N. Clark (Castle Eock) 80 



1. Cretaceous 



