WATER SUPPLY. 313 



afforcling- watering-places for the stock grazing in the open plains or among 

 llui foothills. 



Spearfish and Redwater Creeks united pom- a largo volume of excellent 

 water into the Belle Fourche, but the shales of the Cretaceous ff)nnation 

 through which the river flows soon contaminate the water with alkali, giving 

 it a slightly unpleasant taste, and causing it the past autumn to seriously 

 affect the healtli of the escort. Probably at other seasons the water of the 

 lielle Fourche deserves its name and reputation, but at the time we were 

 camped on its banks (September 20) the stream was comparatively low and 

 the water contained its maximum of impurities. The south fork of the 

 Cheyenne is like most of the river* in the plains, shallow, with a moderate 

 current flowing through a broad level bottom, yet subject to sudden rises in 

 spring and early sunnner. In places it cannot be forded on account of quick- 

 sands, even when the river is so low that the water is but a few inches deep. 



The water of the Cheyenne is full of suspended mud, and contains 

 traces of alkali derived from clays along its banks. 



SECTION III. 

 SOIL. 



There is no better way to judge of the fertility of the soil of a new and 

 unsettled region, wdiere the rain-fall is abundant, than to examine the growth 

 and character of the vegetation which it supports. 



The Black Hills are an oasis of verdure among the open and level 

 plains. A luxuriant growth of grass spreads over the whole region ; even 

 on the rocky hill-sides grass is found growing in the crevices in the rocks 

 wherever there is a particle of soil for its support. A heavy forest covers 

 the greater portion of this area, the trees growing thickly together and 

 attaining full size, not only on the rich bottom lands of the valleys, but on 

 the tops of the level limestone "mesas"; and the steep rocky ridges are 

 clothed with pine of good size to their very crests The soil on the main 

 divides and ridges is not so deep as it is in the parks and valleys which 

 have received the wash from the neighboring hill-sides, and these elevated 



