BLACK HILLS GEOLOGY. 191 



from the massive, horizontal strata which constitute the flat, 

 densely -wooded areas of the Carboniferous plateau. 



In striking contrast to this table-land is the irregular topog- 

 raphy presented by the eruptive region on the east of Spear- 

 fish canon. In the immediate vicinity of the canon itself are 

 found the same narrow precipitous gorges between limestone 

 walls, but as we pass toward the east we find that the country 

 is composed of great numbers of irregular hills and ridges. 

 Some of these are conical in shape, some are dome-like and 

 others present sharp irregular crests, while between them all 

 may be seen many smaller ridges and knolls which greatly 

 complicate and confuse the drainage. A little to the south and 

 east of the center of the district is Terry Peak 7070 feet in alti- 

 tude, the highest point of the northern hills. To the northwest 

 of Terry Peak, Elk Mountain and Ragged Top rise abruptly 

 from the surrounding plateau, the former with a sharp, some- 

 what unsymmetrical contour, and the latter with a broad summit 

 which curves out like a dome and meets the surrounding coun- 

 try in a low, rounded bluff. The two last named hills are much 

 lower in elevation than Terry Peak and for that reason have 

 been generally overlooked in the earlier descriptions of the 

 region. 



Directly east of Terry Peak is the sharp low-lying summit of 

 Sugar Loaf hill from which there is a steep, precipitous descent 

 on all sides. A little more than a mile and a half northeast of 

 Terry Peak rises the beautifully rounded, dome-like mass of 

 Bald Mountain, while immediately to the west and connected 

 to it by a narrow ridge is the hill known as Green Mountain. 

 To the north of Green and Bald Mountains are a group of ex- 

 ceedingly irregular, rounded and conical hills, massed together 

 in a very intricate and confused manner. Of these the most 

 prominent are War Eagle Hill, Richmond Hill and Ragged 

 Butte. 



The drainage of the district is divided into two distinct por- 

 tions. In one the streams drain in a westerly and northerly di- 

 rection into Spearfish creek ; in the other the waters find escape 

 to the north through False-bottom creek, or in a direction more 



