484 



SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION. 





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thickness of the deposit is not more than twenty feet. In its upper half a few streaks of gravel 

 one or two inches thick are to be seen. Above the gravel there is a layer of undoubted clay, 

 covered with blocks of loose and broken basalt. The mass resembles a slide from some higher 

 level or a decomposing rock stratum. Possibly it may be connected with the outcrop of some 

 quartz vein in the vicinity. Certainly it sheds no light upon any of the doubtful questions which 

 have arisen in the study of Table Mountain. 



On the west side of Monte de Oro there have been efforts made, both by surface works and by 

 drifting, to find a gravel channel under the basalt, and gold to a considerable amount is said to 

 have been taken from the locality. I could get no authoritative details in regard to the work here 

 done. By some persons it is thought that gravel was found, though not in paying quantities ; by 

 others, that the basalt rests directly upon the bed-rock. The occurrence of bed-rock at a high 

 altitude in Good's Ravine, the first ravine of prominence to the north of Monte de Oro, lends 

 some support to the latter belief. I determined the altitude of a point on Hendrick's ditch, near 

 the head of this ravine, to be 964 feet. Bed-rock was seen in the ravine at a little higher altitude 



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than this, but still not within a hundred feet of the base of the basaltic bluff. Both the sloping 

 surface of the ground and the bed of the ravine being covered to a large extent with loose blocks 

 of basalt, it was impossible to tell exactly what the material immediately underlying the volcanic 

 cap is. I saw no bed-rock, neither did I see any gravel. This high point of rock is important to 

 notice, for it is said to be the only bed-rock visible at the western base of the main mass of Table 

 Mountain between Monte de Oro and Cherokee Flat. The highest bed-rock seen on the opposite 

 side of Morris Ravine, on the eastern slope of the South Table Mountain, is considerably lower in 

 altitude, not much, if any, over 500 feet. The bed-rock evidently pitches rapidly to the west, and 

 disappears under the detrital material of the Sacramento Valley, not to reappear again east of the 

 Coast Range. See section (Plate X, Fig. 2). The bed-rock seen in Morris Ravine is not easy to 

 name; partly because, when exposed to view, it is apt to be in an advanced state of clayey decom- 

 position, and partly because of certain peculiarities of structure and bedding. The decomposed 

 rock is sometimes yellowish-brown in color, and sometimes a bluish-green, resembling in appear- 

 ance glauconite or green earth. In general terms, however, the most of the rock must be regarded 

 as belonging to the slate family. A few rods below Mr. Ilendrick's house there is some evidence 

 of the existence of a fault in the bed-rock; but, on account of the accumulations of clay and other 

 loose material along the supposed line of strike, it was not possible to tell with certainty. 



Morris Ravine is one of those places from which extraordinarily large quantities of gold are said 

 to have been taken in the early days of placer mining, and it still contains an enormous quantity 

 of undoubtedly auriferous material. The deposit is not exactly like that at any of the other gold- 

 bearing localities in the vicinity ; at least, it is not in the same condition. At the " Point," as it 

 is called, about a mile south of Mr. Ilendrick's house, there are banks, sixty to eighty feet in height, 

 composed of sand and clay of various colors, with horizontally interstratified fine quartz gravel, the 

 pebbles being of the size of beans or peach-stones. In fineness and purity these pebbles remind 

 one of the pebbles at Cherokee Flat, but there is a total lack of the " sand-drift structure," common 

 at the latter place. Possibly there has been a modern rearrangement of the gravel in Morris 

 Ravine since its original deposition. The bed-rock shows none of the ordinary signs of wear com- 

 mon in the beds of old channels. Near the head of the ravine there is a moving and sliding mass, 

 covering from 120 to 150 acres (estimated) of mixed clay, sand, and gravel. It has a slow motion 

 down the ravine in a southeasterly direction. The effects of the slide are seen in several ways. 

 Wave-like ridges are heaped up in front of the moving mass, and upon its surface there are huge 

 cracks, like glacial crevasses, signs of which can be seen even as far back as the base of the basaltic 

 bluff. Mixed with the finer material of the slide there are many boulders, measuring from three to 

 four feet in diameter, and representing many varieties of metamorphic rock, which I could not trace 

 to their origin. Some of these boulders show a peculiar concentric spherical structure. Large sums 

 of money have been spent in the effort to bring water into the ravine in sufficient quantity to work 

 the moving material with profit. When small quantities of water are used, or when the pressure 







