and the Coast
ranges has very little coal. The people of California have to import
large quantities of coal. Some is brought by the railroads from the
Rocky Mountain region, but the most comes by ships from various
parts of the world, from England, Australia, or British Columbia.
The ships bring the coal at low rates and take away grain and lumber.

Coal is almost the only important mineral which Nature has bestowed
sparingly upon the Pacific slope. In California, however, she has made
amends by storing up large quantities of petroleum. In Pennsylvania
and Ohio there is petroleum as well as coal. Oil has also been
discovered in the Rocky Mountain region and in Texas.

[Illustration: FIG. 109.--A SPRING OF WATER AND PETROLEUM

The black streak is petroleum]

Petroleum is found flowing from the rocks in the form of springs,
either by itself or associated with gases and strong-smelling mineral
water. The oil is usually obtained by boring wells, but in southern
California there is one mountain range which furnishes large quantities
through tunnels which have been run into its side. Petroleum is
commonly found in porous sandstones or shales, from one or two
hundred to three thousand feet below the surface. It was not made
in these rocks, but has soaked into them just as water soaks into
a brick. The rocks which produced the oil or petroleum are dark,
strong-smelling shales or limestone. Heat a piece of such rock,
and you will drive out a little oil.

[Illustration: FIG. 110.--OIL WELLS IN THE CITY OF LOS ANGELES,
CALIFORNIA

Pool of oil in foreground]

Examine a piece of the shale from one of the oil districts of
California, and you will discover that it is a very peculiar rock,
for it is made up almost wholly of minute organisms which once
inhabited the ocean. Among the forms which you will find are the
silicious skeletons of diatoms, the calcareous skeletons of
foraminifera, scales of fish, and, rarely, the whole skeleton of
a fish.

Where now there are mountains and valleys dotted with oil derricks,
there was once the water of the open ocean. This water was filled, as
the water of the ocean is to-day, with an infinite number of living
things. As these creatures died, their bodies sank to the bottom, and
while the soft parts dissolved, the hard parts or skeletons remained.
Through perhaps hundreds of thousands of years, the skeletons continued
to accumulate until beds were formed hundreds or even thousands
of f