e of the volcano which we are studying, the lapilli are
so black that they give the cone the appearance of being darkened
by the shadow of a cloud, and on this account the peak is named
Shadow Mountain. As the days are usually bright here, the shadow
effect is very striking.

[Illustration: FIG. 26.--EDGE OF LAVA FIELD, WITH PUMICE IN THE
FOREGROUND

Near Shadow Mountain]

There are several smaller craters, east of the main one, which
also threw out volcanic sand and lapilli. The surrounding hills are
of volcanic origin, although very much older than Shadow Mountain.
These hills are covered with pine forests; but trees or plants
have gained only slight hold upon the newer surfaces of the cinder
cones, which present a picture of almost complete desolation.

There have been two other eruptions since the making of the cinder
cones, and these were marked by flows of molten lava. Although
the rough and rugged surface of the older flow has not yet begun
to crumble and form soil, as it must do in time, yet a few trees
are found here and there, reaching their roots down for the scanty
nourishment to be drawn from the crevices of the rocks.

The last flow of lava, which was very small, ran into a depression
in the other flow just described. This lava appears so fresh that
we almost expect to find the rocks still warm. What a contrast
between the wooded hillside adjoining, with its carpet of soft
volcanic sand, and the jagged surface of the lava! Care must be
taken in climbing over the lava, for the sharp points and angles
are ever ready to tear one's shoes and hands. It cannot be many
years since these hard, cold rocks formed a glowing mass of molten
matter creeping quietly out of some hidden fissure which reached
far down into the earth. The lava hardened as it became cold, just
as does molten iron when led from the furnace to make a casting.

At one spot in the lava field stand the remains of rude stone houses
built into caverns in the lava. About them are scattered pieces
of broken pottery. These rude dwellings were probably occupied by
some of the prehistoric people whose homes are also found along
many of the streams, and in the caves of the plateau region. We
can see no reason for their coming to this desolate place, so far
from a water supply, unless it was that the rugged lava offered
some protection from their enemies.

Now let us imagine ourselves transported to northern California.
Near Lassen Peak, the sout