129. Coal.

Coal is dug from layers or beds
in the ground. The patches of
color on. this map show where
these beds are found.

Coal is formed chiefly of great
ferns,’ mosses and rushes that grew
in vast swamps, long ages ago.
These plants made thick woody
layers in the swamps.

In some way these layers were
buried in mud, upon which other
plants grew. For ages and ages
the work went on, till there were
many layers of woody plants buried
deep in beds of mud.

This wood was slowly changed
ito coal, and many of the’ beds
of mud also became rock.

In place of the old swamps there are now
broad fields and long mountain ridges, but the
hard layers of coal are still under the surface.

1 See the tree ferns on page 53.

COAL.

97

 

By digging into some of the ridges, or deep

in the fields, people take out the brown or
black layers to burn.
More than one half the coal used in the

United States is taken from the mines of Penn-

 

mgitude 105 West

 

Greenwich

 

 

 

 

 

sylvania. Illinois
ranks second and
Ohio third. .

When hard coal is
taken from mines,
much of it is in
large pieces. These
are crushed be-
tween heavy iron
or steel rollers in
great buildings,
called breakers.

The boys in the
picture are picking
slate from coal, as
it slides down a
long trough or
chute.