THE GRAVELS THE WORK OF RIVERS. 293 
From the historical summary presented in a previous chapter,* it will have 
been seen that, previous to the investigations of the California Survey, 
there were a variety of opinions current in regard to the nature and origin 
of the gravel deposits. Scientific men in general looked upon these detrital 
accumulations as having been formed by the agency of the sea, which spread 
them uniformly over the slope of the Sierra, while their present occurrence 
at various elevations and in detached areas was accounted for by subsequent 
supplementary upheavals of the range and the irregular erosion arising there- 
from. That these views, based on very insufficient explorations, and quite 
at variance with almost all the prominent facts, can no longer be held by 
any one who is acquainted with the region in question, may be unhesitat- 
ingly asserted. That the gravels have been formed and deposited by the 
agency of fresh water may be set down as positively determined. 
The idea that the gravels were of fluviatile origin having gained ground 
among the miners of the region even before it was accepted by scientific 
observers, it was quite generally held that it was essentially one stream 
which did the work; or, at least, that the most important and valuable 
gravel deposits, especially those represented by the ‘blue-lead,” belonged 
to one system of drainage, and that this was parallel to the present crest of 
the Sierra. This was, probably, the most popular theory current among the 
miners at the time the writer began his work in California. Some persons 
even connected the sources of this north and south running stream with 
regions far beyond the limits of California, and diverted the waters of the 
Columbia so as to bring them into connection with the monster river by 
which the blue-lead was originated. What peculiarities there were in the 
position and mode of occurrence of the gravels which led to the adoption of 
such strange views will have been made sufficiently apparent from a perusal 
of the preceding pages.t | 
We may now proceed one step farther than we could at the time of the 
publication of Geology, Vol. I. It had then (1865) been clearly made out by 
the labors of the Geological Survey, that the high gravel-deposits were exclu- 
sively of fluviatile origin, or, in other words, the work of ancient rivers ; but 
in regard to the relation of this old system of drainage to the present one 
but little has been definitely ascertained. It could be stated that it had been 
shown by our explorations that the materials of which the gravel deposits 
* See ante, pp. 66-74. 
+ See also Mr. Goodyear’s remarks in regard to the ‘‘ blue-lead theory” in Appendix B. 
