PEALE.] 



GEOLOGY — SECTION NO. 13. 225 



company. The works, which have been quite extensive, are now entirely- 

 deserted. Grossing the stream to the butte north of the works, we discover 

 at the base exposures of gray sandstones laminated, and containing gyp- 

 sum. These sandstones seem to dip toward the north. In some places the 

 gypsum seems to be interbedded, and in others occurs only in ])ockets. 

 Ascending the butte, we find on the top trachyte, very much like that 

 on the butte east of the works. The slope for some distance is covered 

 with debris from this rock. It is probably a portion of an overflow that 

 was once continuous toward Buffalo Peaks, for to the west, on a line 

 between it and the peaks, is a third butte capped in the same manner, 

 having gypsiferous beds at the base. The gypsum is very impure com- 

 pared with that found in the hog-backs outside the mountains. East of 

 the salt-works the line of the volcanic material has a direction toward 

 the southwest, to the divide between South Park and the Arkansas 

 Kiver, where we shall speak of it again in a subsequent portion of this 

 chapter. The range on the west side of the xiark, the Park range, is 

 for the most part composed of sedimentary formations, which have been 

 thrown up, and dip toward the park. There are a number of extensive 

 faults, the down-throw being always on the west side. This, however, 

 will be rendered clear as we proceed. We will return to the northwest 

 part of the park and commence the consideration of this range with 

 Mount Lincoln, one of its highest peaks. Mount Lincoln and Mount 

 Bross have both become widely known since the discovery on them of 

 extensive deposits of silver-bearing galena. The mines here will be 

 described in the mining report of Dr. Endlich. Mr. Taggart ascended 

 Mount Lincoln from the town of Montgomery, and in speaking of the 

 geological structure I will quote frequently from his notes. On the 

 west side of the Platte Eiver, below Montgomery, he made the following 

 section : 



Section No. 13. 



Ascending order : 



1. A light colored quartzite, very much broken up. The weathered sur- 



face is greenish. The dip is 12° to north of east, 20 feet. 



2. Gray crystalline limestone, conformable to No. 1. It has bands of 



laminated gray limestone, varying from a foot to a foot and a 

 half each, 12 feet. 



3. Limestone very much like that of No. 2, only darker in color, 15 feet. 



4. Cherty limestone, 12 feet. 



Mount Lincoln is 14,121 feet above sea-level. It is capped with a 

 trachytic rock, as seen in Pig. 5, Plate VJ. This is probably the result 

 of a flow from a dike ; erosion has carried away so much material that 

 it is isolated, and it resembles a bed that is contemporary. At one point 

 on the northeast spur of the mountain Mr. Taggart says he found a 

 well-defined dike, about 10 feetin width, which seemed to extend through 

 the bends. 



On the ridge running toward Mount Bross Mr. Taggart made the fol- 

 lowing partial section : 



Section No. 14. 



1. Soft and brittle carbonaceous shale, 6 feet. 



2. Gray quartzite, with bauds of a dark ferruginous quartzite one to 



two feet each, 78 feet. 



3. Laminated micaceous sandstone, 2 feet. 



15 G s 



