very
rapidly, while wood piled or packed close together so as to exclude
the air, or left in the shade and exposed to rain and snow, will dry
out very slowly and will also be subject to mould and decay.

But seasoning implies other changes besides the evaporation of water.
Although we have as yet only a vague conception as to the exact nature
of the difference between seasoned and unseasoned wood, it is very
probable that one of these consists in changes in the albuminous
substances in the wood fibres, and possibly also in the tannins,
resins, and other incrusting substances. Whether the change in these
substances is merely a drying-out, or whether it consists in a partial
decomposition is at yet undetermined. That the change during the
seasoning process is a profound one there can be no doubt, because
experience has shown again and again that seasoned wood fibre is very
much more permeable, both for liquids and gases than the living,
unseasoned fibre.

One can picture the albuminous substances as forming a coating which
dries out and possibly disintegrates when the wood dries. The
drying-out may result in considerable shrinkage, which may make the
wood fibre more porous. It is also possible that there are oxidizing
influences at work within these substances which result in their
disintegration. Whatever the exact nature of the change may be, one
can say without hesitation that exposure to the wind and air brings
about changes in the wood, which are of such a nature that the wood
becomes drier and more permeable.

When seasoned by exposure to live steam, similiar changes may take
place; the water leaves the wood in the form of steam, while the
organic compounds in the walls probably coagulate or disintegrate
under the high temperature.

The most effective seasoning is without doubt that obtained by the
uniform, slow drying which takes place in properly constructed piles
outdoors, under exposure to the winds and the sun and under cover from
the rain and snow, and is what has been termed "air-seasoning." By
air-seasoning oak and similiar hardwoods, nature performs certain
functions that cannot be duplicated by any artificial means. Because
of this, woods of this class cannot be successfully kiln-dried green
from the saw.

In drying wood, the free water within the cells passes through the
cell walls until the cells are empty, while the cell walls remain
saturated. When all the free water has been removed, the cell w