CHARACTER OF THE GRAVEL: PLACER COUNTY. 93 
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stratum of sand; and over this, again, the same “chocolate” as at the Reed Mine, resting hori- 
zontally on it. On the rim-rock the gravel disappears and the “chocolate” rests directly on the 
bed-rock. In both the Reed and the Rattlesnake claims the “ chocolate” shows no indication of 
bedding or lamination. 
In the Basin Channel, at the Devil’s Basin, the average thickness of the gravel on the bed-rock 
was about two and a half feet, though it sometimes reached five or six feet. Immediate] y above 
the gravel was a stratum of the “chocolate” volcanic mud about two feet thick, and above this a 
bed of “ gray cement” similar to that in the Reed Mine, which at one point where they raised up 
through it was found to be twenty-five feet thick, and to be overlain by another stratum of aurif- 
erous gravel of unknown thickness, resembling in character that upon the bed-rock itself, excepting 
that the boulders it contained were smaller and the gold was finer. Silas Griffett’s Claim is located 
on the trail, at the Devil’s Basin at the point where he believes the Basin Channel enters the 
Deadwood Ridge. The gravel in this claim is of about the same character as that in the Basin 
Channel, but is some ten or twelve feet thick on the bed-rock in the hydraulic face, and is overlain 
by about fifteen feet of exceedingly fine sand mixed with some clayey matter, and very thinly bed- 
ded in horizontal layers. 
At Hornby’s Tunnel, near Deadwood, the gravel runs all the way from a few inches to two feet 
in thickness. Over it lies the “chocolate,” and above this as in the Reed Mine lies the “gray 
cement,” which here, however, contains numerous smooth rounded volcanic pebbles and boulders, 
some of which will weigh over 200 pounds ; these are usually very fine-grained, hard and tough. 
At Weske’s Claim, near Michigan Bluff, the layer of gravel is very thin, averaging probably 
not over a foot, although deeper in the depressions of the bed-rock. The quantity of quartz in 
the gravel is not large. It consists chiefly of metamorphic pebbles, with a few volcanic ones inter- 
mingled. Immediately above the gravel comes a heavy mass of “gray cement,” similar in charac- 
ter to that of Reed’s Mine, near Deadwood ; the thickness of this bed of ‘ cement” is unknown. 
In many places the gravel “shuts out” entirely, and the cement lies directly on the bed-rock. 
Yet even in such places the bed-rock sometimes pays; and, when there is only a little sand 
between the cement and the bed-rock, it is frequently rich. In Van Emmon’s hydraulic claim, at 
Michigan Bluff, the gravel is from twelve to fifteen feet thick. It is overlain by a bed of sand, 
which at the point exposed when the locality was examined by Mr. Goodyear was about three 
feet thick. Above this there was another streak of gravel, of about a foot in thickness, and above 
that a material which they here call ‘‘ cement,” though it probably contains nothing volcanic, and 
consists of a very tenacious clay mixed with some sand, and containing a good deal of very fine 
gravel. The gravel in general is moderately hard and the majority of the pebbles and boulders of 
which it is made up are of quartz, though with these occur many of metamorphic rock. At the 
Specimen Claim, in Byrd’s Valley, the gravel is very largely quartz, and many of the quartz boul- 
ders are of great size, weighing several tons ; these are considerably water-worn, although not per- 
fectly rounded. 
-At A. Bowen’s Tunnel, near Michigan Bluff, the gravel averages a foot or two in thickness in 
the middle of the channel, and on the rims it runs out entirely. Over the grave! is, first, a mass 
of “chocolate” from one to four feet in thickness; above this the “ gray cement,” similar in 
character to that at the Reed Mine, near Deadwood. The chocolate also runs out on the rim- 
rock, and the gray cement closes down on the bed-rock. This gray cement is supposed to be from 
forty to fifty feet in thickness ; the chocolate contains leaves of deciduous and coniferous trees in 
tolerably good preservation. 
At Ayer’s Claim, near Michigan Bluff, the gravel is well washed, but consists chiefly of volcanic 
boulders, which range from a few pounds to a ton in weight. At El Dorado Hill, near Michigan 
Bluff, the maximum height of the hydraulic bank is about 100 feet. There is very little quartz in 
the gravel here, the boulders being chiefly volcanic and not very large. 
At the Dam and El Dorado claims; in the West Fork of El Dorado Caion, between five and 
six miles north of Michigan Bluff, the gravel varies from nothing to seven or eight feet in thick- 
