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510 



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rilE BLUE LEAD THEORY. 



Exceptions to this statement may be found, of course, and bodies of gravel are by no means rare 

 whose general color to-day is largely due to the original character of the rocks from which they 

 were derived. But the general rule is as stated above. 



Another objection to the whole blue lead theory, and one which to my mind is insuperable, 

 lies in the simple fact that this theory presupposes or of necessity involves a great subsequent 

 upheaval of the whole Sierra Nevada, as it is evident that at no time since the upheaval of the 

 range could any river have flowed far in a southeasterly direction along its southwestern slope. 

 Moreover, the subsequent upheaval which this theory requires is not merely a moderate lifting, by 

 which the altitude of a previously existing range might have been somewhat increased, but a grand 

 and general uplift, essentially creating and calling into new existence the Sierra as a mountain- 

 range ; for, otherwise, the same objection would still hold good against the direction of its rivers. 

 However low may be the crest of a range of mountains, if it exist as such at all, or if the country 

 has even a very light general slope, the rivers do not run far in the directions of the contour 



lines. 



Now I do not know of any evidence whatever to prove that any such upheaval as this has 



occurred since the gravel period. On the contrary, there is abundance of evidence which appears 



to me very strong as tending to show not only that no such upheaval has occurred, but also that 



no considerable disturbance of any kind whatever has occurred in the auriferous slates or in the 



mass of the range itself since the earliest gravel period. Indeed, I do not believe that since that time 



there has been sufficient disturbance of the bed-rock in any part of the Sierra where I have been 



to influence to any perceptible extent the general flow of even the smaller streams. The streams, 



both large and small, have changed their beds indeed, but it has been in another way and from 



another cause. 



A fact which, in connection with other things, appears to me conclusive as evidence that no 

 considerable disturbance of the bed-rock has occurred since the gravel period, is the almost total 

 absence of local disturbances since that date. It is difficult to believe that any considerable 

 general disturbance of such a range of mountains could occur at any time without producing at 

 the same time numerous smaller and local disturbances in the way of faults, dislocations, bendings 

 of the strata, etc. 



If such disturbances as these had occurred since the deposition of the gravel banks, then these 

 banks themselves would have been correspondingly disturbed and faulted, and their sections would 

 exhibit it when they came to be worked. Such things do indeed exist, but they are extremely 

 rare ; and I do not know of a single instance where such a disturbance exists of so great a magni- 

 tude that it may not be reasonably attributed to earthquake shocks not greatly exceeding, perhaps, 

 in violence some which are already on record as having occurred within the State. I may say 

 that, in all my travels in the gravel region, I met with but a single case of such a disturbance (the 

 one at Yankee Jim's) in which I considered the proof absolute and unquestionable that the dis- 

 location was more recent in date than the gravel period, and here the amount of displacement was 

 only some twelve or fifteen feet. Other possible localities arc King's Hill, between Indian and Shirt 

 Tail canons, the "Dardanelles, Flora's claim below Volcanoville, the Castle Hill ridge a little way 

 above Georgetown, and Spanish Hill near Placerville, though I consider some of these as very doubt- 

 ful, to say the least, and there has certainly been no great displacement in any case. Moreover, the 

 bedding of the gravel is almost everywhere horizontal, or very nearly so ; and, excepting at Yankee 

 Jim's and perhaps two or three of the other localities named, I never saw this bedding distinctly 

 broken or otherwise disturbed or bent to such an extent as could not be readily accounted for by 

 the action of the shifting streams which deposited it, or else by special and. wholly local causes, as 

 in the cases where the gravel rests upon the limestone. 



"When these things are considered in connection with, the facts respecting the present directions 

 and grades of the ancient channels in the bed-rock, wherever these have been distinctly and defi- 

 nitely traced, and with a multitude of other facts in the distribution and structural arrangement 

 of the gravel itself, all pointing in the same direction, I consider it proved beyond all reasonable 



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