ACADEMY OF NATURAL SCIENCES. 391 



Grade," another outcrop of the same formation has been cut across in building 

 the road, and here a portion of the same flinty rock is thickly tilled with fossils, 

 which appear to belong either to some species of crinoids or fu'coids, though the 

 structure is too much obliterated, and the specimens too much distorted to admit 

 of definite recognition. They are apparently flattened in a direction parallel 

 with the banding of the rock. From the general mode of occurrence of this 

 hornstone, and from the frequent sharp and distinct lines of demarcation between 

 it and the adjacent hornblendic rock, it might be inferred that the former trav- 

 ersed the latter as veins, and the delicate banding of the rock, although parallel 

 to the general stratification of the country, would not preclude such an assump- 

 tion. But the fossils speak decidedly against it, and it is probable that the 

 hornstone is a metamorphic form of fine sedimentary deposits, and that the band- 

 ing is the result of the original stratification. Quartz veins occur here occa- 

 sionally, and some of them at least are auriferous, though I know of none having 

 been worked with profit hitherto. It is not improbable, however, that some of 

 them may be found remunerative in the future, since many of the gulches among 

 the hills here, in the early days of mining, were rich in placer gold. The degree 

 of metamorphism throughout these hills has been very high ; but I have seen 

 no evideuce of any direct igneous action — at least no rock that I could identify 

 as eruptive, with the single exception, perhaps, of a small and apparently com- 

 pletely isolated body of well characterized granite, which occurs near the base 

 of the Gopher Range, and between its highly metamorphosed rocks and the San 

 Joaquin Valley, which is overlaid with tertiary and other recent formations. 

 The occurrence of this patch of granite here, isolated as it seems from any other 

 similar rock, is certainly a point of much interest ; but I have not been able to 

 study its relations. Its stratigraphical and topographical position is similar to 

 that of the Folsom granite, and it may be connected with it in origin. If it 

 should hereafter appear that that there is a well characterized, though more or 

 less interrupted line of granitic outcrops traceable throughout central California, 

 along the lower foothills of the mountains, and west of the great belt of aurifer- 

 ous slates, it would have a most important bearing upon the theory of the general 

 structure of the Sierra Nevada. The existence of such a line, indeed, might 

 point to a very different, and perhaps more probable, modus operandi than that 

 already suggested, by which the auriferous slates themselves may have reached 

 their present position, and received their easterly dip. 



One of the most interesting points connected with the geology of the Gopher 

 Hills, is the auriferous belt in which occurs the "Quail Hill " Mine, and of 

 which I shall -speak further presently. 



Of the geology of Bear Mountain I know but little, having crossed it by but 

 a single route. Where I have seen it, however, it consists largely of a similar 

 rock to that which forms the mass of the Gopher Hills. Chromic iron is said 

 to occur in considerable quantity at a certain locality in Bear Mountain, the 

 exact whereabouts of which I could not learn. The slates of the valley extend, 

 in general, completely up to the base of the Gopher and Bear Mountain ranges 

 on either side, and sometimes a short distance up their flanks ; but here the 

 transition to the harder crystalline rock is usually quick and well marked. 



