GEOLOGY. 299 



that has been so often maintained, that all, or even a portion, of the 

 auriferous slates are older than the carboniferous, not a trace of a 

 Devonian and Silurian fossil ever having been discovered in Califor- 

 nia, or indeed anywhere to the west of the 116th meridian. On the 

 other hand, we are able to state, referring to the theory of the occur- 

 rence of gold being chiefly limited to Silurian rocks, that this metal 

 occurs in no inconsiderable quantity in nietamorphic rocks belonging 

 as high up in the series as the cretaceous. 



The cretaceous formation in California is also extensive, and em- 

 braces to a great extent the coast ranges of both California and 

 Oregon. The formation, however, so far as known, is represented 

 on the Pacific coast by but a single member, the upper or white 

 chalk. 



In regard to the relative ages of the different mountain chains of 

 the Pacific coast, Prof. Whitney says : 



" There can be no doubt that the chain of the Sierra Nevada is 

 older than the Rocky Mountain chain, or that group of chains or 

 ranges which forms the eastern border of the great mountain region 

 of the western side of the continent. The great mass of the Sierra 

 was uplifted and metamorphosed after the termination of the Jurassic 

 epoch, and prior to the deposition of the Cretaceous, for we find the 

 last-named formation resting horizontally and unaltered on the Hanks 

 of the Sierra, all through Central California." 



" We have recognized at least three distinct peripds of upheaval 

 and metamorphic action in the coast ranges. The main one 

 was at the close of the Cretaceous epoch ; the next in importance 

 was after the deposition of the Miocene tertiary, or, at least, 

 of a group of strata which, for the present, may be referred to that 

 age. The next in age is a system of east and west upheavals, which 

 took place at the close of the Miocene ; and the third is one which 

 appears to have commenced during the later Pliocene, and to be still 

 going on. 



" It is a very interesting fact that the exterior of the coast ranges 

 that is to say, the mountains nearest the Pacific are of earlier date, 

 or older geologically, than the interior ones, or those which border 

 the Sacramento and San Joaquin valleys. This is a repetition on a 

 smaller scale of what has been the course of events in the formation 

 of the whole continent, the exterior lines having been first marked 

 out, and the interior filled up afterwards. 11 



The vast detrital deposits on the flanks of the Sierra Nevada, where 

 hydraulic and tunnel mining operations for gold are carried on, arc of 

 tertiary age. It has been assumed that they were of marine origin, 

 but an examination of them has proved to the contrary, as is proved 

 by the fact that, although frequently found to contain impressions of 

 leaves, masses of wood and imperfect coal, and even whole buried 

 forests, as well as the remains of land animals, and occasionally those 

 of fresh water, not a trace of any marine production has ever been 

 found in them. 



Again, these detrital deposits are not distributed over the flanks of 

 the Sierra in any such way as they would have been if they were the 

 result of the action of the sea. On the contrary, there is every rea- 

 son to believe that they consist of materials which have been brought 



