82 GEOLOGICAL SURVEY OF THE TERRITORIES. / 



some and Willow Greeks, aud between those two streams, the aggregate 

 thickness of the Liguitic group cannot be less than 4,000 feet, and it is 

 probably greater even than that. This is made up of sandstones of 

 various texture with partings of clay, the entire mass having the dark, 

 somber hue which characterizes the same group about the sources of 

 the Missouri and Yellowstone Eivers. 



These beds have been so thoroughly studied by Mr. Marvine that I 

 allude to them in this connection simply to call attention to the possi- 

 bility that they elid not form a connection originally with the same 

 group on the east side of the range. The differences in thickness and 

 in lithological character of all the sedimentary groups in the Middle 

 Park, as well as their position, .indicate that a portion of the Front 

 range was elevated above the sea, thus cutting off this portion from 

 the east side. Although the peculiar flora of the Lignitic period is 

 very abundant in the Middle Park series, no beds of coal have been 

 observed as yet, and in this respect they offer a marked difference. 



I have hitherto been disposed, from the original evidence shown at the 

 northward, to regard the physical connection of this great Lignitic 

 group on opposite sides of the mountain-ranges as proven, but there is 

 some doubt on this point, and I now await further proof. 



