78 DESCEIPTIVE GEOLOGY. 



distinctions observed elsewhere. In the upper part of the series, the most 

 characteristic Jurassic hmestone has a flesh-red color, with a uniform texture 

 mixed with considerable fine, angular grains of sand. No well-defined 

 organic remains were found, but the rock shows indistinct fossiliferous frag- 

 ments. 



This limestone was subjected to chemical analysis by Mr. B. E. Brewster, 

 with the following result : 



Silica - 22. 218 



Ferric oxide and alumina 0. 210 



Lime ----- - 43. 237 • 



Magnesia 0. 150 



Carbonic acid 33. 937 



Water 0.140 



99. 890 

 which, when combined, yields — 



Carbonate of lime 76. 748 



Carbonate of magnesia 0. 321 



Along the east side of the plains, the Dakota sai^dstones may at times 

 be recognized, cropping out above the accumulations of Quaternary debris, 

 sufficiently well defined to trace their horizon. At the north, the beds 

 appear to incline westward, with an angle of 2° to 3°, but become hori- 

 zontal to the south. They crop out just east of Lake lone, and, so far as 

 observed, are found only on the east side of the Laramie River till within 

 6 or 7 miles of Laramie City, which they appear to underlie as well as 

 Fort Sanders, and to form the banks on both sides of the river; on the 

 west side rising above the stream in a low rounded ridge, sloping west- 

 ward. ^ 



The rock is a yellowish-brown, medium-grained sandstone, Avith some 

 carbonaceous material scattered through the upper beds. 



South of the railroad, the Triassic, Jurassic, and Dakota Cretaceous, 

 following the boundary of the Archaean, curve around to the southwest, 

 lying inclined at not more than from 1° to 4° toward the plain. The Tri- 

 assic Red Beds rest directly on and overlap the granites, jutting up against 



