FIEST STATEMENTS OF THE GEOLOGICAL SURVEY ABOUT THEM. 73 



meet with opposition. It was necessary to make another step in advance 

 and to show that the rivers were not one but many, and that the direction 

 of the drainage was, when those high gravels were accumulated in the 

 channels of the ancient streams, not essentially different from what it now 

 is. It was necessary that the position of the gravels and the intercalated 

 and overlying volcanic deposits should be laid down with accuracy on a map, 

 and that the course of each separate stream should be followed up with a 

 series of measurements of elevation, so that continuity or non-continuity 

 could be asserted with confidence as an established fact, and not guessed at. 



The work of the State Geological Survey was, for various reasons which it 

 is not necessary here to explain, chiefly carried on during the first years in 

 the Coast Ranges, and in 18G2 - 63 there was only time for a rapid 



recon- 



naissance in the mining region of the Sierra. 



rn 



The general results of this 



a con- 



preparatory work, in so far as the high gravels were concerned, were given 



ft ^*" 



m the following words in a resume of the progress of the Survey, published in 

 the American Journal of Science, for September, 1864 : "There is perhaps 

 no subject connected with the geology of the Pacific coast in regard to which 

 there arc so many misapprehensions as there arc in what has been published 

 by geologists on the nature and distribution of the detrital deposits which are 

 so extensively worked by the methods known as hydraulic and tunnel min- 

 ing. It has been assumed that these deposits are of marine origin, and that 

 they originally extended over the whole slope of the Sierra Nevada,— 

 dition of things which, were it true, it would be of vast importance for Cali- 

 fornia to know ; but the real facts of the case are entirely different. In the 

 first place these deposits are not of marine origin, 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 

 <^ny 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 w r ould have been if they were the result of the action of the sea. 

 On the contrary, there is every reason to believe that they consist of 

 materials which have been brought down from the mountain heights above 

 wid deposited in preexisting valleys : sometimes very narrow accumulations, 

 Simple beds of ancient rivers, and at other times in wide Like-like expansions 

 of former watercourses ; and this under the action of causes similar to those 



* 



now existing, but probably of considerably greater intensity. This deposition 



