THE GEAVEL: EL DOEADO COUNTY. 



99 



ville, more than nine tenths of the whole mass of the gravel is of volcanic origin, and all the peb- 

 bles are very smoothly rounded. 



At the Webber Claim, about a thousand feet east of the Excelsior, and on the south side of 

 Coon Hollow Ridge, where an acre or more lias been washed off, the bank is a little over a hun- 

 dred feet in height The upper twenty-five or thirty feet arc. of the so-called " black lava," and 

 beneath are sixty or seventy feet of smoothly rounded " mountain gravel/' The metamorphic 

 gravel, lies on the bed-rock, and varies from two or three to twenty feet in thickness, according to 

 the inequalities of the surface of the bed-rock. The mountain gravel is said to contain gold enough 

 to pay all expenses of wages and water. At Webber Hill the maximum thickness of the gravel is 

 forty or fifty feet. It is overlain by white lava, which, in the eastern part of the hill, is from 

 seventy-live to one hundred feet thick, and shows a decided tendency to assume columnar forms. 

 Above this is u mountain gravel," forming the crest of Webber Hill. 



At the Confidence JVline, 300 or 400 feet north of the Hume at the head of Cedar Ravine, the 

 slope goes down with an inclination of five feet in twelve and is 300 feet long to the bed-rock. 

 On the bed-rock is a stratum of gravel from five to eight feet in thickness, overlain by the " white 

 lava," winch extends all the way to the surface. In Cedar Ravine, near Dickerhoffs Mill, the 

 white lava shows something of a tendency to a columnar or prismatic structure. 



At DickerhoiFs Mine in Cedar Hill the pay-gravel in the channel on the bed-rock is from three 

 to four feet in thickness, and is made up almost entirely of pebbles of metamorphic rock, with 

 much quartz, a good deal of which is but little rounded; it is immediately overlain by a body of 

 exceedingly fine-grained, compact material, called by the miners " lava," and which, in fact, appears 

 to be of volcanic origin. It is believed to be of great thickness, perhaps from 100 to 200 feet, and 

 it is capped by the " black lava,," which is also fully a hundred feet in thickness, in all probability. 



Just east of Dickerhoffs Mill in the north side of Cedar Hill, the hydraulic banks are from 

 fifty to sixty feet high, the lower few feet only being a true gravel, and all the upper part of the 

 banks consisting of sands and clays. In tho hill immediately back of the banks these finer sedi- 

 ments are also overlain first by eight or ten feet of " white lava," then by a body of "mountain 

 gravel," and finally the latter is capped with a mass of "black lava." 



At the Hook and Ladder Claim in Big Spanish Hill, about one mile nearly east of riaeerville, 

 the gravel on the bed-rock averages from four to six feet in depth, and is covered by from fifteen 

 to twenty-five feet of sand, above which come heavy beds of still finer sediment, containing occa- 

 sional thin streaks of fine gravel ; and over all a few feet of volcanic cement, the whole height of 

 the bank being about a hundred foot. 



On the north side of Little Spanish Hill, about the head of Spanish Eavine, the gravel has a 

 total thickness of sixty to seventy feet. At the height of twenty-five or thirty feet above the bed- 

 rock it is traversed by a stratum of mottled white and rose-colored " pipe-clay " six or eight feet 

 thick. Below this " pipe-clay " is a mass of fine sand with some clay but no pebbles. But above 

 it is pebbly gravel, which shades off again at the top into fine sand and clay, immediately beneath 

 the final capping of "black lava." 



a 



The section of the bank, at this point, is as follows : — 



Volcanic breccia . , . . . . . 



Very fine sand, irregularly bedded ........ 



Streak of white pi j H'.-clay .......... 



Fine gray gravel, and sand 



Pipe-clay ," pinkish and rather hard 



Sand, reddish below and bluish at top ....... 



Gravel, father fine, with some sand 



Total height of hank 



There arc places in Little Spanish Hill, where tho volcanic capping is seventy-five feet thick. 

 The order of superposition of the different materials in the banks above the bed-rock, in Ham: 



Foot. 



10- 



12 



4 



-6 







-1 



8- 



10 



8- 



12 



15- 



20 



10- 



15 



5 to s< I feet, 





