FIRST 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 1862-63 there was only time for a rapid recon- 
naissance in the mining region of the Sierra. The general results of this 
preparatory work, in so far as the high gravels were concerned, were given 
in the following words in a réswné 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 are so many misapprehensions as there are 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, — a con- 
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 
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 reason to believe that they consist of 
materials which have been brought down from the mountain heights above 
and deposited in preéxisting valleys: sometimes very narrow accumulations, 
simple beds of ancient rivers, and at other times in wide lake-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 
