able Mountain of California is a
massive natural railway embankment or colossal Chinese wall, extending
through several counties, but best studied in Tuolumne County.

The mountain is forty miles long, from five hundred to eight hundred
feet high, and a quarter of a mile wide at the top. For the most part
the top is bare of vegetation and quite level, though slanting slightly
toward the south. In places at the base of its precipitous sides, and
sometimes extending part way up, pine and other trees are found growing.

This gigantic wall, broken through in several places by flowing rivers,
is nothing more nor less than a mighty stream of congealed basaltic lava
called latite, which in prehistoric times, rushing down the western
flank of the high Sierras, usurped the bed of an ancient river channel,
drinking up the waters and piling up its molten mass bank high.

The bed of the stream being filled with lava, its waters not flowing
through the gravel, were forced to find other channels. The action of
the elements during subsequent ages has worn away in great part the
banks of the pliocene river and eroded in places the solid slate rocks
to the depth of two thousand feet, leaving this sinuous wall as a mute
witness of the mighty forces of nature.

On account of the excessive hardness and durability of this kind of
basalt, this monumental fortress will endure long after the corroding
tooth of time shall have crumbled to dust the royal pyramids and their
very memory shall have been lost in oblivion.

Some geologists think there were two volcanic streams of lava, one
succeeding the other by an interval of thousands of years, the first
covering the auriferous gravel and the second quenching the waters of a
subsequent river which had forced a passageway through the first flow of
lava.

Scores of tunnels have been run into the mountain to get at the gravel
of this Pactolian river. Millions of dollars of gold have been extracted
from its bed, and millions more await the tunnel, upraise, and drift of
the adventurous miner.

Beginning at the top of the mountain and working downward, we find the
order of materials as follows: A cap of basalt from sixty to three
hundred feet thick, a bed of breccia of varying thickness, two hundred
feet of conglomerate andesitic sand (volcanic ash of the miners), a bed
of pipe-clay, and then auriferous gravel resting on a bedrock of slate.
In tapping the ancient river-bed considerable water is e