ervation require that
a forest should be cut and not merely held untouched. But it also
demands that the cutting shall be done on scientific principles, and
that only as much timber shall be removed in a given time as the
forest can produce in a corresponding period. After the cutting, the
forest must be left in a condition to produce another crop of
timber within a reasonable time: see Fig. 122. These fundamental
requirements represent the difference between conservative lumbering
and ordinary lumbering. Besides insuring a future supply of timber,
conservative lumbering, or lumbering on forestry principles, also
tends to preserve the forest floor and the young trees growing on
it, and to prevent injury to the remaining trees through fire,
insects and disease. It provides for a working plan by which the
kind, number and location of the trees to be cut are specified, the
height of the stumps is stipulated and the utilization of the wood
and by-products is regulated.

Conservative lumbering provides that the trees shall be cut as near
to the ground as possible and that they shall be felled with the
least damage to the young trees growing near by. The branches of the
trees, after they have been felled, must be cut and piled in heaps,
as shown in Fig. 122, to prevent fire. When the trunks, sawed into
logs, are dragged through the woods, care is taken not to break down
the young trees or to injure the bark of standing trees. Waste in
the process of manufacture is provided against, uses are found for
the material ordinarily rejected, and the best methods of handling
and drying lumber are employed. Fig. 135 shows a typical sawmill
capable of providing lumber in large quantities.

In the utilization of the by-products of the forest, such as
turpentine and resin, Forestry has devised numerous methods for
harvesting the crops with greater economy and with least waste and
injury to the trees from which the by-products are obtained. Fig.
136 illustrates an improved method by which crude turpentine is
obtained.

[Illustration: FIG. 136.--Gathering Crude Turpentine by the Cup and
Gutter Method. This system, devised by foresters, saves the trees and
increases the output.]

Forestry here and abroad: Forestry is practiced in every civilized
country except China and Turkey. In Germany, Forestry has attai