260 
GEOLOGY. 
thousand feet, pouring from the top of the ridge into the valley below. After winding about 
in circuitous ravines between the edges of horizontal strata, capped in some places by basaltic 
layers high above us, we reached the Cave House, built at the base of a ridge of the white 
limestone, the continuation of the same which occurs further south, at Columbia and beyond. 
At this point the trend is from N. 50° W. to N. 75° W., and the beds incline towards the east 
at a high angle. The trend is remarkably distinct, the rock being weathered in long parallel 
lines corresponding to what was probably the original stratification of the rock. 
We entered and explored the u Great Cave.” It consists of a series of passages and cham¬ 
bers of great extent, worn in the rock by the solvent power of water holding carbonic acid in 
solution. These chambers are irregular, and generally the trend of the limestone is distinctly 
shown in the walls and ceiling by the irregularity of the decomposition or solution of the rock, 
some of the layers being much more rapidly acted on than others, precisely as we find on the 
surface. 
Several of the chambers are lined with stalactites and stalagmites of great beauty. The 
stalactites often reach from the ceiling to the floor of the caverns, and thus form grottos with 
alahaster-like walls, presenting a splendid appearance when illuminated by candles. Nearly 
all of the lime which is thus deposited is highly crystalline, and reflects back the light of the 
candles from myriads of brilliant facets. Where the calcareous water has oozed from fissures 
in the walls, and ran down to the floor, great deposits of the crystalline lime have been formed, 
and they appear at a little distance like foaming water-falls, so perfect is their resemblance to 
them in shape. 
MURPHY’S TO SACRAMENTO. 
August 9.— Murphy's to Mokelumne Hill, 34 miles .—At Angel’s camp, ten miles from Murphy’s, 
the talcose slates come into full view, and are traversed by quartz veins. At one of the mines, 
a thin vein of quartz bears a quantity of white iron pyrites and gold. The pyrites is also found 
in the adjoining slates in brilliant cubes, forming interesting cabinet specimens. The slates 
are light-colored, and like those which are similarly charged with pyrites in North Carolina. 
The veins appear to be conformable with the slates, and trend a little west of north. Several 
outcrops of the slate seen before reaching Angel’s camp were nearly east and west in their trend, 
and were inclined at an angle of about 45° towards the north. 
We reached the outskirts of Mokelumne Hill after dark, and came near driving into the 
mouth of an open pit, one of the abandoned mining shafts which line the road on each side. 
This town is one of the oldest in the mining region, having been commenced in 1849, and it has 
been noted as one of the richest mining localities in the southern mines. It is on the south side 
of, and over a thousand feet above, the Mokelumne river. It is well supplied with water, under 
a pressure of 110 feet, from a reservoir. The mining is chiefly in a coarse drift of gravel and 
boulders, many feet below the surface. I am informed that the gold is nearly all coarse, and 
that the greatest part is in grains worth from fifty cents to ten dollars. A high hill adjoining 
the town is composed of horizontal strata, chiefly soft and semi-consolidated clays, and fine sand 
of volcanic origin. They are not well exposed to view, hut a part of the hill extends out in a low 
spur, formed of a comparatively hard stratum of a peculiar pink sandstone, composed in a great 
part of pumice-stone and its fine dust. This stone is quarried in large blocks, and being very 
light and easily cut, is sent down to San Francisco for the erection of a block of buildings. It 
