THE GEEEK EIVEE COAL BASIN. 457 



below the railroad crossing. Medicine Butte, a prominent mountain rising 

 about the level of the Tertiary plains, is an anticlinal mass of the coal fold. 



After a careful laying down of all known outcrops, with their dips and 

 strikes, it has been found that the system within the limits of this survey 

 consists of three broad folds, having their rise at the base of the Wahsatch, 

 and continuing quite parallel to an indefinite distance, with a course of north 

 26° east. Of these three folds the central is the most important. Its 

 average breadth is about twelve miles upon each side. The broad, general 

 anticlinal is fluted in minor waves. Near the west are seen the relics of 

 another fold, the synclinal between these two being occupied for a considera- 

 ble distance by the canon of the Weber. The curious outcrop known as the 

 Needle Rocks, just below Echo City, belongs evidently to the easterly slope 

 of this fold, and the rocks seen up Lost Creek indicate its further continuance 

 in that direction. So far all the coal mines of any importance belong either 

 to the central fold or to the minor corrugations of its sides. Coalville, the 

 Winship beds, Bear Eiver, and Evanston are all a part of this central fold 

 system. Its further continuance is indicated in the central mass of Medicine 

 Butte. Erosion has not only removed a large part of the superimposed Ter- 

 tiary series, but it has carved away very much of the fold itself, laying bare 

 strata which belong to its greatest depths and exposing freely the coal which 

 belongs certainly 2,000 or 3,000 feet from its summit. From Bear Kiver 

 City to Green River there are no important outcroppings of the formation. 

 Those sandstones which crown the " Quaking Asp" divide may possibly belong 

 to it, but if so their relations with the later Tertiary have decidedly changed, 

 passing from different planes to entire conformity. On the east side of the 

 Green River the coal series reappears, and occurs with more or less con- 

 tinuity quite through Wyoming Territory and Colorado. The division east 

 of the Green River has been worked up by Dr. Hayden, and also is well 

 treated in the report for the benefit of San Francisco capitalists, by Messrs. 

 Ashburner and Janin, mining engineers. 



Our knowledge of the formation is now so well advanced that it can be 

 said with perfect safety that the series contains a practically inexhaustible 

 supply of coal. Beds from 7 to 25 feet in thickness are discovered at inter- 

 vals over 500 miles, and from their ordinarily gentle dips may be mined with 

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