398 GEOLOGICAL EXCURSION TO THE ROCKY MOUNTAINS. 



The road ascends rapidly through these Tertiary beds, the gradient, 

 in the last 7 miles (11 km.) before reaching Soldiers Summit, being 

 3| per cent, or 200 feet (01 in.) to the mile (1.01 km.). 



Soldiers Summit is at the erest of the Tertiary watershed, which lies 

 from 20 to 40 miles (32 to (it km.) to the east of the erest of the Wasatch 

 range. The road now descends the valley of Price river nearly to the 

 Colorado river, through a region of almost horizontal Mesozoic and 

 Tertiary beds which are uninfluenced by the Wasatch upheaval. This 

 region is not only of modern geological formation, in that it is traversed 

 by no known lines of long continued dynamic movement, and hence 

 owes its topographical form entirely to erosion, but its erosion is of the 

 type peculiar to an arid or practically rainless region whose streams 

 are fed only by the precipitation on high areas outside of the region. 

 This erosion is produced primarily by the streams in their narrow beds, 

 whose winding course was first determined on a comparatively level 

 surface of unconsolidated and easily abraded beds. The first charac- 

 teristic of such a drainage system, as distinguished from one that is 

 built up on the drainage systems of earlier geological periods, is its 

 comparative independence of the obstacles opposed to its course by 

 the relative hardness, or the position of older strata, which it has 

 reached after cutting its bed down through the uniform and softer 

 overlying strata. This produces the effect designated "inconsequent 

 drainage." 



From Pleasant Valley a branch runs southward up the main fork of 

 Price river to the coal mines in the Laramie Cretaceous at Scofield. In 

 the reddish beds about a mile (1.01 km.) north of Pleasant Valley st a 

 tion are found veins of ozocerite or mineral wax. This and allied 

 hydrocarbons are found abundantly in the beds of the Green River 

 Korene at various points in the basin region between the Wasatch and 

 the Rocky mountains. A gray limestone near the station contains 

 fresh water mollusks, which may prove to belong to this period. 



The road descends rapidly in geological horizon, as well as topo- 

 graphically, and in a few miles enters the massive gray sandstones of 

 the Laramie Cretaceous, in which Price river has cut a narrow, wind- 

 ing, and ever-deepening gorge, whose walls show a great variety of cas- 

 tellated forms due to erosion. The finest of these is just above Castle- 

 gate, where a narrow column of sandstone, over 500 feet (152 m.) high, 

 stands at the end of a sharp, narrow ridge like the watch-tower of a 

 castle. 



At Castlegate is a coal mine with coke ovens, which obtains coal from 

 a seam near the base of these massive sandstones. 



As the road descends below the coal horizon of the Laramie, through 

 the more thinly bedded sandstones of the Fox Hills formation which 

 contain an ever-increasing proportion of clay shales, into the readily 



