EASTEEN FOOTHILLS. 31 



The beds are made up almost exclusively of sandstones and limestones, 

 and show but little evidence of slates, clays, marls, or mud-rocks. But, 

 with the exception of the lower quartzite and sandstone, all the sandstone 

 strata appear more or less calcareous, and the limestones, through most of 

 the horizons, indicate more or less arenaceous material; while the heavily- 

 bedded massive limestones frequently carry intercalated narrow beds of sand- 

 rocks and fine conglomerate. 



The lower sandstones are exceedingly variable, occasionally appearing 

 as a hard compact rock, and in other localities developing a loose friable 

 conglomerate, consisting of pebbles and fragments of older rock. They 

 are, however, everywhere characterized by a prevailing reddish tint; the 

 upper beds showing considerable persistency as a coarse, bright red sand- 

 stone. 



In general, the limestones develop a dark bluish-gray color with bands 

 of various colored beds. The upper limestones are usually lighter in color, 

 frequently shading off into pink and white, and possessing a saccharoidal 

 granular texture. The beds which form the steeper ridges, lying inclined 

 at angles varying from 75° to the vertical position, show all the divisions 

 in the series much less distinctly marked than the less altered beds inclined 

 with a gentle uniform dip. In many localities the limestones in these highly- 

 metamorphosed ridges are so much altered, as to present a very marked dif- 

 ference in lithological character; the beds being changed into compact, hard, 

 cherty strata, and the purer limestone, as in the ridge north of the entrance 

 of the Chugwater Canon, altered into a coarse white marble. 



Dolomitic limestones appear to characterize the base of the formation ; 

 at least in the region of Granite Canon the beds show the presence of 

 more or less magnesia. They are marked by a compact very fine-grained 

 texture, and uneven fracture. Fragments treated with dilute acids dissolve 

 slowly, usually leaving a slight residue of silica in fine angular jp*ains. 



A small fragment of a nearly pure magnesian limestone from Granite 

 ^anon was submitted to chemical analysis by Mr. B. E. Brewster, with the 

 following result: 



