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REVIEW AND GENERAL DISCUSSION. 



503 





on the same channel, which probably flowed from Little Spanish Hill across Cedar Ravine to 

 Cedar Hill, and then traversed the latter obliquely in a southwesterly direction to Coon Hill. 



There are some difficulties, or at least some points which are very unsatisfactorily explained, in 

 the way of such a theory. Yet the heavy banks at Spanish Hill and Coon Hill resemble each 

 other so closely in their general character, and in so many of the details of their structure too, 

 while the furrowings of the bed-rock on the south side of Little Spanish Hill are in the right 

 direction for it, and the bed-rock in Cedar Hill at the proper point is known to be low enough 

 for it, and the banks of metamorphic gravel which are visible at the latter point, though bearing- 

 no comparison in point of magnitude with the masses of Coon and Spanish hills, are yet the 

 heaviest masses of that material to be seen anywhere along the northern side of Cedar Hill, that, 

 so long as I know of nothing in Cedar Hill that is positively prohibitory of it, I am still inclined 

 to hold, that theory. But if it be true, then it is possible, either that this stream may have been 

 a, branch of the one flowing westerly near Webber Creek, or that it may have been not at all 

 contemporary with it, but entirely an independent stream at some other time. It is, in any case, 

 impossible now to say where this stream came from to the east or northeast of Spanish Hill. 

 There are no more banks resembling these now visible in any of the hills around the head or on 



the other side of Hangtown Creek. 



There are many facts which seem to point to a probability that a considerable stream once 

 flowed southwesterly through Negro Hill, and the little outliers beyond, known as Little Indian 

 Hill, Indian Hill, and Clay Hill. The predominant part which a certain dark-colored volcanic 

 sand, free from pebbles and boulders, plays in the formation of most of the banks at these locali- 

 ties speaks strongly in favor of their close connection in origin, and the lay of the bed-rock is such 

 as to accord with this idea. But the exact localities whence this stream came, and where it went 

 to are alike uncertain. It was in all probability a considerably more recent stream than the one 

 which flowed in the blue lead channel above described, from White Rock to Smith's Flat, etc.; 

 and it is possible, though by no means certain, that it may have flowed transversely over and 

 across that channel, in the ridge just south of White Rock. 



Any further attempts to trace out definite channels in the vicinity of Placerville would prob- 

 ably be useless now. The banks are everywhere full of unmistakable evidence of the multiplicity 

 of chances undergone by the streams which gathered them, and the process must have been a slow 



and Ions one. 



The frequent white lava boulders which occur in the gravel in the deepest portions of the 



channel beneath Smith's Flat, as well as the occasional ones found in the lower gravels at Webber 



Hill and elsewhere, are interesting as proofs of the fact that the volcanoes were already active in 



the High Sierra long before the great masses of volcanic matter now capping these, hills and 



ridges came here, and that, even while some of the earlier gravels about Placerville were gathering, 



there existed somewhere in the higher northeastern country masses of these white volcanic ashes, 



already consolidated into a rock from which boulders could be made. The white lava also, 



wherever found, appears to be the earliest kind of volcanic matter that was afterwards spread over 



this region. 



And the occurrence at Prospect Flat (a fact, by the way, which has its parallel perhaps at 



Smith's Flat also, and certainly at many other localities in the country I studied last summer) 

 of thin strata of metaniorphic, quartzose, and auriferous gravel, intercalated between bodies of 

 white lava, high above the bed-rock, proves that, after the first heavy bodies of volcanic matter 

 reached here, the streams still flowed, passing some of the way in their new courses over the 

 naked surface of the higher and still uncovered bed-rock, and again over the surface of the vol- 

 canic mallei' already accumulated, and so, here and there, spreading thin local sheets of meta- 

 morphic gravel far and. wide over the volcanic floor already laid above the older gravel. 



Then came other floods of volcanic matter, and sometimes other sheets of gravel, and so on 

 through the slow-moving changes. At other localities, instead of spreading gravel over the earlier 

 bods of volcanic ash, the streams seem to have excavated new channels through them, sometimes 



