BED-ROCK: AMADOR COUNTY. 87 
masses. There are streaks and patches of slates and sandstones connected with the granite, making 
it a difficult problem to unravel the geology in this region. At Brownsville, there is a belt of lime- 
stone, the surface of which is worn into all sorts of fantastic forms ; this rock cannot be traced for 
any considerable distance, and is apparently not more than a few hundred feet in width. The same 
limestone occurs again at Indian Diggings, on Indian Creek, where there appear to be several thin 
belts or patches of this rock. Many of the huge fantastic blocks into which the limestone has been 
eroded, or weathered, have been broken off and rolled down into the Creek below, so that it is 
difficult to say when the rock is in place and when not. At the last-mentioned locality the bed- 
rock, when not limestone, is slate and sandstone, all thoroughly decomposed and soft. This de- 
composed material has belts, patches, and bunches in it through which is distributed a certain 
quantity of rolled pebbles of quartz and other rock, the whole forming a curious pot-pourri of decom- 
posed bed-rock and gravel. There are portions of the rock in which no water-worn pebbles are 
found ; but-in other places there is a great abundance of them scattered about in an irregular way. 
Some of the belts in which they occur are but a few feet wide, and stand nearly vertical ; others 
are more or less inclined ; others horizontal, or nearly so, while some are quite irregular in posi- 
tion. It is said that whenever these rolled pebbles are found distributed through the rock, the latter 
contains gold enough to pay for washing ; and that, when they do not occur, this is not the case. 
It appears probable that, as the creek slowly cut its way down through the soft bed-rock, there took 
place, from time to time, a great deal of sliding of the ground; and that the gravel, which once 
overlaid the surface of the bed-rock, has thus become irregularly incorporated with its soft mass. 
The most common direction of the strike of the slates in the immediate vicinity of Volcano is 
northeast and southwest. At the head of the Flat the slate strikes northeast; though at the 
foot, just below the town, it runs about north. These rocks are not unfrequently much contorted ; 
and the outlines of the limestone masses occurring here are very irregular. In the caiion of Sutter 
Creek, a little way below Volcano, there is a large quantity of well-characterized talcose slate, 
called “soap-stone” by the miners; but there are also considerable bodies of very hard, fine 
grained, nearly black silicious rock, which is very tough and massive. Limestone forms the bot- 
toms of all the workings in Indian, Jackass, and Soldier’s Gulches, near Volcano ; and it also 
makes up the lower portion of the spurs which separate these gulches. The surface of this rock, 
especially in the spur between Indian and Clapboard Gulches, is worn out into holes and cavern- 
ous places of the utmost irregularity of form, with fantastic pinnacles between them. These 
cavities are filled with gravel, and are often as much as forty or fifty feet in depth. The flat which 
stretches along Sutter Creek, above Volcano, is from 500 to 600 feet in width, and, for 
nearly its whole length, it has been extensively worked by sinking pits, raising the gravel by 
derricks, with whims driven by horse-power, and washing it in sluices. These pits have been 
worked down, sometimes, to a depth of forty or fifty feet, over a width of from 300 to 400. The 
surface consists of a dark-colored soil, from three to eight feet in depth, and beneath this lies the 
gravel, the general level of which rises but a few feet above the average level of the higher por- 
tions of the limestone, whose surface, as in other localities, is worn into the most fantastically 
shaped cavities. As Mr. Goodyear remarks, ‘ No words can paint the raggedness of these 
excavations.” * Similar phenomena may be observed on the right bank of the South Fork of 
Sutter Creek, near Aqueduct City, about six miles southwest of Voleano ; at this point a considera- 
ble area of the limestone has been worked off, or uncovered by mining. The rock here, as in sev- 
eral other portions of the limestone belt, is intersected by numerous dykes of diorite, which traverse 
it in an easterly and westerly direction. These dykes vary from two to thirty feet in width ; 
some are even wider than thirty feet. On the right bank and near the mouth of Soldier's Gulch, at 
Volcano, there is a locality of complex forms of chalcedony. Close by it there is a rocky point e»a- 
sisting entirely of a perfectly honey-combed mass of thin, flat sheets of chaleedonic and jaspery 
quartz. This rocky knob is from thirty to forty feet in height, and about the same in diameter. 
* The claim at the upper end of Volcano Flat, where the limestone has the most ragged appearance, is 
called the “ Upper Engine Claim.” 
