CHARACTER OF THE GRAVEL: PLACER COUNTY. 95 
wanting. But even here the soft bed-rock is said to be rich and to have paid, over much of the 
area thus situated, almost as well as where there was gravel. There are still to be seen rich 
streaks in the gravel, “lousy with gold,” to use the miners’ phrase. The Back Channel* is be- 
lieved to be rich, having been sufficiently prospected to prove this. The gravel appears to be 
deepest in the deeper portions of the channel; but it is not deep enough to cover the high bed- 
rock, nor does its upper surface lie level; but, to a considerable extent, it conforms to that of the 
bed-rock itself, especially in the larger channels. Numerous quartz boulders have been found here 
rich in gold, and some of them were remarkable. For instance, it is stated that one boulder 
weighing only twenty-nine pounds contained $3,700 in gold, which metal made up more than one 
third of its weight. 
In the region lying between the heads of the three cafions, known as First, Second, and Third 
Brushy, directly north of Forest Hill, and from one to three miles distant from that place, there is 
a large amount of gravel. Some of this is uncovered ; other portions have a deep covering of vol- 
canic material. The gravel varies much in thickness, ranging from a few feet to as much, perhaps, 
as three hundred. A peculiar feature of this region is, the great depth to which much of the vol- 
eanic conglomerate has been decomposed. This decomposition has developed in a remarkable 
degree the concentric structure of the volcanic boulders. These are banks in which, almost with- 
out exception, every boulder will exhibit this structure, with sometimes a hard kernel in the centre, 
and sometimes without one. Another feature of this district is, the frequency of streaks or beds 
of auriferous gravel overlying the volcanic cement. Distinct channels can with difficulty be traced, 
in the region in question, on account of the wide diffusion of the gravel, the deep covering of vol- 
canie material with which it is overlain, and the very limited extent to which the bed-rock itself 
has been exposed to view. 
At Smith’s Point, between First and Second Brushy cajions, in the banks exposed by the 
hydraulic operations, the gravel ranges from fifty to sixty feet in thickness. It is made up of peb- 
bles and boulders of metamorphic rock chiefly, with some of quartz; they are generally under 
twenty-five pounds in weight. The gravel is in places more or less interstratified with beds and 
streaks of sand, which are not continuous for any great distance, and which are not exactly hori- 
zontal, but slightly inclined in various directions. Above the gravel lie alternating beds of ash, 
more or less clayey, and volcanic conglomerate, occasionally containing very large boulders. Far- 
ther back on the crest of the ridge the regular volcanic conglomerate occurs in heavy masses. 
- At Yankee Jim’s the gravel is composed of all sorts of metamorphic rocks, and few boulders 
are met with which are too large to wash through the sluices with a good head of water. The 
proportion of quartz is small. Over the central axis of the Big Channel the gravel averaged, for 
most of the distance, over a hundred feet in thickness ; and the average over the whole ground 
washed was, probably, forty feet. Over almost the whole of this ground the gravel was uncovered ; 
but at the east end it is overlain by the volcanic cement, which here also shuts out a considerable 
portion of the thickness of the gravel. 
At Georgia Hill on the south side of the Devil’s Cafion, a little below Yankee Jim’s, an area has 
been washed off 600 or 700 feet long by an average of 100 wide ; in the western. half of this 
ground the gravel was uncovered and reached a depth of 100 feet or more, but the eastern half 
was covered with volcanic cement which in going easterly from the middle of the ground worked 
gradually descends, and nearly shuts out the gravel. 
At the Oro and Dardanelles claims, near Todd’s Valley, the lower portions of the banks consist 
of blue gravel. Above this in the Oro and the eastern part of the Dardanelles is red gravel to the 
top; but in the central and southwestern portion of the last-mentioned claim the upper heavy 
bank of red gravel is overlain by a mass of voleanic cement, whose maximum thickness, so far as 
it is exposed, is not far from 100 feet. The gravel is generally very hard ; and the banks, even 
where they have not been touched for five years, are usually very smooth, and often very nearly 
* See page 106 for a description of the so-called Back Channel. 
