GRAVEL AND VOLCANIC FORMATIONS : CALAVERAS COUNTY. 



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could be run through the sluices. That this could be done with profit, 

 •as must have been the case from the length of time the operation was car- 

 ried on, — shows that the gravel must have been quite rich in gold. The 

 continuation of the Mokelunme Hill channel below Chili Gulch, towards 

 Double Springs, lias, apparently, not been found worth working to any 

 considerable extent. 



In that portion of Calaveras County which lies to the southeast of the 

 river of that name there are numerous localities where gravel deposits occur 

 under the volcanic materials; but none of these are of great extent, or 

 have been worked very continuously. The localities where these gravels 

 occur are chiefly in the vicinity of San Andreas, Altaville, and Vallecito. 



The gravel deposits at San Andreas have been worked in former years to 

 considerable extent. The formation appears to be from 100 to 150 feet 

 in thickness. A section, as given by two of the miners at this place, will 

 be found farther on, in the chapter devoted to the remains and works of 

 man in the gravel under the volcanic beds. The eruptive masses here would 

 appear from their position to be connected with the flow which has come 

 down from the Sierra behind the Big Tree Grove, and which passes about 

 two miles north of Cave City, and is there known as Table Mountain, a 

 name very commonly given in California to lava flows, and especially to 

 isolated patches of such flat-topped masses. 



In the vicinity of Douglass Flat and Altaville there is a large develop- 

 ment of volcanic materials, and some gravels which have been worked from 

 time to time. There is a, nearly level tract of land extending north from 

 Vallecito to Douglass Flat, known as Vallecito Flat, which is an area de- 

 pressed below the surrounding region, and filled to a considerable depth by 

 gravel, of which the exact limits seem to be not well known. The bottom 

 of this depression is too deep to be drained, except by a long tunnel, and 

 such a one was commenced many years ago, but never completed. A tunnel 



■ 



from the forks of Coyote Creek, about a mile in length, would, it is supposed, 

 open this ground at a sufficient depth to permit its being worked by the 

 hydraulic method. There is an elevated ridge of volcanic breccia extending 

 along the northwest side of Vallecito Flat, which rises to a height of nearly 

 600 feet above the lower portions of the surface of the Flat, and the Sonora 

 Table Mountain extends, with a nearly equal elevation, along the east side, 

 occupying most of the space enclosed between Murphy's, Douglass Flat, and 

 Vallecito Flat on the west, and the Stanislaus River on the east, as far as 



