cr own readers

214 USES OF FORE STS.
its way to th e streams, and when it is actually in
th e brooks , its progress down ward is retarded by
numerous dams made of fallen timber and drift-wood.
Th e result is that instead of pouring swiftly to the sea,
th e flood waters creep slowly away, requiring week >;
in place of hours for their journey to the greater
rivers.
6. Th ere is another effect which forests have upon
the soil. Th e strong roots of trees, penetrating far
down in to the sub soil and into the crevices of th e
rocks, draw upward and build in to their trunks th e
solid matter wh ich we find in th e ash of burnt wood.
Th e trees also gather a large par t of their substance
from the atmosphere. All the material which goes
into the air when wood is burnt came from the air
during the growth of the plan t. Wh en the tree dies,
or wh en its leav es and branches fall, this mixture of
decayed vegetable matter is mixed with the soil, and
serves to increase its fertility. The farmer has to
imitate th e natural process which goes on in the
forest, and introdn ce similar subs tances into th e soil
in order to main tai n its producti veness.
7. From the forests we derive the tim ber which
constitutes a large par t of our houses, and whi ch is
also necessary for the construction of our agricultural
machinery, of part of onr ships, and of a host of
other st ructures which are essential to the well-being
of man.
8. Although mineral coal has, in the more civilized
parts of the world, to a great extent taken t he place
of wood for heating pur poses, probably three-fourths
of the domestic hear ths in the world are still supplied
from th e forests. It is to be hoped that the use of