2o2 DESCEIPTIVE GEOLOGY. 



the standstones near Black Butte Station, which, however, on account of their 

 wide range and the want of direct correspondence in the flora of this region 

 with that of the Atlantic coast, or of Europe, are of little value in the deter- 

 mination of the geological horizon. 



To the west of Black Butte Station, the sandstone ridges, which, near 

 the railroad, are degraded and much obscured by clayey and shaly debris, 

 become gradually higher and more prominent. The peak of Black Butte, 

 which is a prominent landmark in the region, attaining a height of over 

 8,000 feet, is formed of one of these more massive sandstone beds, whose 

 horizon corresponds with those exposed in the country to the west of Point 

 of Eocks Station. It has apparently been preserved from erosion by local 

 metamorphism. The summit consists of a huge homogeneous block of 

 sandstone, some 50 feet cube, whose upper surface is thoroughly vitrified, 

 while the lower part still preserves the soft friable nature of the sandstones 

 of this region; this metamorphism only penetrates a few feet within the 

 rock, and presents a regular gradation from a glassy state, almost like a 

 slag, to that of a loose granular sandstone which crumbles between the 

 fingers. 



Along Bitter Creek, to the west of Point of Eocks Station, and in the 

 dry stream-bed to the eastward, a more continuous section is afforded at 

 right angles to the strike. Throughout this section there is little variety in 

 the general lithological- character of the beds. The exposures are princi- 

 pally sandstones, gray and brown, more or less stained by iron oxide. But, 

 as shown in the section made by the artesian boring at the railroad-station, 

 beds of clay and shale form no inconsiderable portion of the formation, 

 though, being much more easily eroded, they are not seen on the surface. 

 Some of the sandstones give slight effervescence with acid, but the amount 

 of calcareous material is comparatively unimportant, and due probably to 

 the percolation of waters charged with carbonate of lime. Throughout the 

 whole section are found seams of coal, which, however, have been more 

 explored in the upper part of the section in the neighborhood of the railroad- 

 station. The coal beds carry a good deal of iron pyrites, to the decompo- 

 sition of which is probably due the fact that almost all the springs in the 

 vicinity are strongly impregnated with sulphur. There is a beautiful sulphur 



