s 



THE GRAVELS THE WORK OF RIVERS, 



29° 



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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 a-ained 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.f 



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 

 m 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. 

 t See also Mr. 



Goodyear's remarks in regard to the "blue-lead theory" in Appendix B. 



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