mnwp^ 



iHpMttdMHMnMM'HP«P«lPIIMMM 





















K 



500 



GRAVEL DEPOSITS NEAR PLACERVILLE. 



in place. So far as these facts go, therefore, they point to at least a probability that a stream of 

 some magnitude once flowed here for several miles in a general southeasterly or southerly direction 

 before bending southwesterly to the normal course of the Sierra streams ; and, whenever the region 

 about and above here comes to be accurately mapped, it will be seen that this is precisely what 

 is done by several of the longest modern branches of the Middle Fork of the American. Duncan 

 Canon, the Middle Fork of the Middle Fork, and the South Fork of the Middle Fork, all do the 

 same thing. And, in fact, the upper drainage basin of the Middle Fork of the American expands 

 northeasterly, around and to the east of the Canada Hill Bald Mountain, in such a way that the 

 streams which drain its farthest limits in this direction mast flow southeasterly and southerly hero 

 for a number of miles before they can bend southwesterly to their normal course. Probably a 

 similar state of things in this respect existed here also in the gravel period. 



From all that I was able to learn, it appears that to the south of the line of water-shed between 

 the South and Middle Forks of the American, and between it and the South Fork, there is nowhere 

 any considerable quantity either of ancient gravel or of volcanic matter. In other words, almost 

 all the gravel and volcanic matter between the South and Middle Forks is on the northern drainage 

 slope, where the water runs to the Middle Fork. 



But, on crossing the South Fork of the river, we find again, in the region about Placerville, 

 extensive and very complex accumulations both of gravel and volcanic matter. I spent con- 

 siderable time in this vicinity, and the preceding detailed notes relating to it are very full.* 



In passing from this mass of detail to general considerations, the most salient point, and the first 

 conclusion which presents itself, will probably be the complexity and apparent confusion of 

 structure in the gravel and volcanic banks throughout this region, and the extreme difficulty, if 

 not indeed the impossibility, of tracing out to-day any definite system of contemporaneous streams 



which may have existed at any one particular time during the long period of the slow accumu- 

 lation of these banks. 



Indeed, I may say that with all the time and study that I gave to this amphitheatre of hills 

 surrounding Placerville, and all the detail I was able to gather respecting them, I do not consider 

 it practicable yet (with a single exception only) to trace continuously with any definite certainty 

 for any considerable distance the course of even a single stream at any particular time. 



There are, indeed, at various localities where the bed-rock is hard, as at Webber Hill, Little 

 Spanish Hill, etc., systems of parallel furrows worn in the surface of the rock, which show, as I 

 conceive, with tolerable certainty, the directions of latest flow upon the surface of the rock at these 

 localities. And if the bed-rock were generally hard enough beneath the gravel so that the miners 

 would not disturb it in their operations, we should probably see these fm rowings wherever it is 

 uncovered, and their study might become an extremely interesting as well as complex problem. 

 But, unfortunately for this, the bed-rock beneath the gravel is far oftener than otherwise thoroughly 

 decomposed, and so soft that in drifting, as well as in hydraulic work, from six inches to a foot 

 of its surface is generally taken up on account of the gold which has worked its way into its 

 crevices, etc. 



Moreover, it is by no means certain, and, indeed, I consider it altogether improbable, that all 

 these furrowings, even in the surface of the bed-rock itself, are contemporaneous in their origin. I 

 think it more than probable that, if the bed-rock were everywhere hard, and if the gravel and vol- 

 canic matter overlying it were all removed, so that its ancient surface could be minutely studied, 

 we should find in these furrowings an intricate system of directions, — perhaps with a general 

 westerly and southwesterly trend, — but still intricate enough to be capable of explanation only 

 by the theory of shifting streams, the gradual filling of the deeper channels, and the frequent local 



4 



turning of the water in new directions over higher and still higher portions of the rocky surface 

 till finally all was buried. 



In all the complex structure of the higher portions of the banks themselves above the surface of 

 the rock, I find, almost everywhere, what seems to me indubitable proof, not only that these banks 



* See ante, pp. 98, 101, 108, 111, 112, 119, 120. 



