position to this conclusion it has been urged that the stone
mortars, pestles, etc., have become imbedded in the gravel by the action
of streams, or slips from the mountain side in modern times, or are the
results of interments or mining operations.<15> As an illustration of
how they might become buried by the action of streams, reference is made
to somewhat similar discoveries in the tin-bearing streams of Cornwall
(Wales). We know with considerable certainty that at a very early date
the Phoenicians worked in the gravels of these streams for tin ores.
Implements made use of by them and others--such, for instance, as
shovels, mortars, pick-axes, stone bowls, and various dishes--have been
found at all depths in this gravel, by more modern miners.<16>

This may explain the presence, in some instances, of similar remains in
California, but it utterly fails to do so, where the remains have been
buried underneath a lava flow or a bed of volcanic materials, as is the
case in many of the instances we have cited. Manifestly no water has
disturbed their strata since the volcanic materials were laid down.
Neither can we think of a land-slide carrying these remains into the
heart of a mountain, or burying them underneath a hundred feet of lava.
The peculiar position in which they were often found is surely lost
sight of by those who think they might have been placed there by
interment. We can not think of a savage people digging a grave in such a
position.

It has been urged with considerable force that these relics have been
left behind by ancient miners when they mined for gold. Dr. Wilson is
cited as authority for the statement that the Mexicans obtained "silver,
lead, and tin from the mines of Tasco and copper was wrought in the
mountains of Zacotollan by means of galleries and shafts, opened with
persevering toil where the metallic veins were imbedded in the solid
rock." Prescott, the historian, also testifies to the same fact.

We need only add to this, that wherever these ancient galleries were
opened in the solid rock, they still exist. Schoolcraft mentions
finding one two hundred and ten feet deep.<17> The chances are not worth
considering, that these old mines would be overlooked. If, for instance,
the Calaveras skull is that of a prehistoric miner, killed in an old
mining gallery only a thousand years or so ago, it is inconceivable that
all evidence of this mine should have disappeared. Or, if in one case
it should h