CENTEAL Am) EASTBEK NEVADA. 335 



derlie and are conformable witli the limestones that form the eastern ex- 

 tremity of the slope. Both slates and hmestones are traversed by numerous 

 veins of quartz, some of which show good bodies of galena ; these veins have 

 a north and south strike generally conformable with the stratification. 



On the lower face of the foot-hills, just north of the mouth of Santa F^ 

 Gallon, are the remarkable glacier polishings already mentioned. A thin seam 

 of gray quartz, striking north 15° east, with a dip of 59° east, here forms the 

 face of the spur; its somewhat undulating surface has, on the salient parts, 

 over a tolerably continuous extent of several hundred feet, received a mirror- 

 like polish, equal to the finest produced by artificial means, so that when the 

 sun's rays strike upon it at the proper angle their reflection is visible as a 

 bright point from a distance of many miles. The lines of striation, which are 

 only visible on a close examination, are parallel to the line of greatest inclina- 

 tion. The surrounding rock, which is a somewhat metamorphosed and slaty 

 limestone, has not been of sufficient hardness to retain any other traces of 

 glaciers, though it is evident that to this agency must be attributed these pol- 

 ishings. Their position is indeed singular, at the foot of such a steep slope, 

 and entirely on the outside of the canon basin ; the head of this canon, which 

 extends up to the northeastern crest of Bunker Hill, must have been filled by 

 a glacier, whose lower end overlapped this spur, which closes up, in a meas- 

 ure, the mouth of the canon, and the descending mass of ice and gravel has 

 worn away the less resisting rocks, while this sheet of quartz received its 

 present high polish. As far as known this is the only instance of such ice 

 polishings in the range, though, as elsewhere remarked, the shape of the inte- 

 rior valleys seems to indicate that they were once filled by glaciers. In the 

 limestones of Santa F6 Canon were found the fusilinae already mentioned. 

 Near the mouth of the canon is a dike of dark green, fine-grained syenite, 

 consisting of hornblende and white feldspar, the former occasionally in colum- 

 nar crystals ; no quartz or mica are found in this rock. 



Bunker Hill, the second highest peak in the range, (11,735 feet,) holds a 

 central position, geologically as well as topographically ; its neighborhood, after 

 the Twin River region, has been the scene of the most varied upheavals and 

 metamorphisms, and the strike of its rocks forms the greatest angle with the 

 general direction of the range. Its mass consists of the various slate series 



