o its side, it is just as bare and perfect in form as when first
completed.

Little by little the forests are encroaching upon the sand-covered
slopes about the cone, and in time these slopes, the black fields
of lava, and the cone itself, will be covered with forests like
the older lava fields and cinder cones which appear upon every
hand.

THE MUD VOLCANOES OF THE COLORADO DESERT

The Colorado Desert is a strange, weird region. Here is a vast
basin at the head of the Gulf of California which was once a part of
the gulf, but is now separated from it by the delta of the Colorado
River. With the drying up of the water, the centre of the basin was
left a salt marsh more than two hundred and fifty feet below the
level of the ocean. In summer the air quivers under the blazing
sun, and it seems as if no form of life could withstand the scorching
heat, but in winter the atmosphere is cool and full of life-giving
energy.

Around this desert rise the mountains, some old and nearly worn
down, their tops barely rising out of the long slopes of sand and
gravel; others rugged and steep, lifting their crests far above
the burning desert into the cold, clear sky.

Curious forms of plants and animals find their homes upon the slopes
about the basin, where they adapt themselves to the heat and dryness.
But toward the centre the soil is bare clay, for when the water dried
up so much alkali and salt were left that nothing could grow.

However we do not now intend to study the plants or the animals,
interesting though they are, but rather a group of mud volcanoes,
which forms almost the only relief in the monotony of the bare
plain. These volcanoes are in no way related to real volcanoes
except in shape, for water and mud, instead of fire and lava, have
been concerned in their building.

[Illustration: FIG. 30.--MUD VOLCANOES, COLORADO DESERT]

Once it required a long journey in wagons or upon horseback to reach
the mud volcanoes, but now the railroad takes us within three miles
of the spot. We alight from the train before a section house which
stands in the midst of the great desert. Far, far away stretches the
barren clay floor of the ancient lake. Here and there are scattered
stunted shrubs, the only specimens of plant life which have been
able to withstand the alkali in the clay.

Seen from the station, the volcanoes appear like dark specks almost
upon the horizon, but in reality they are not far away, and an
hour's