ore difficult it is
to dry wood. Wood shrinks about twice as much tangentially as
radially, thus introducing very serious stresses which may cause loss
in woods whose total shrinkage is large. It has been found that the
amount of shrinkage depends, to some extent, on the rate and
temperature at which woods season. Rapid drying at high or low
temperature results in slight shrinkage, while slow drying, especially
at high temperature, increases the shrinkage.

As some woods must be dried in one way and others in other ways, to
obtain the best general results, this effect may be for the best in
one case and the reverse in others. As an example one might cite the
case of Southern white oak. This species must be dried very slowly at
low temperatures in order to avoid the many evils to which it is heir.
It is interesting to note that this method tends to increase the
shrinkage, so that one might logically expect such treatment merely to
aggravate the evils. Such is not the case, however, as too fast drying
results in other defects much worse than that of excessive shrinkage.

Thus we see that the shrinkage of any given species of wood depends to
a great extent on the method of drying. Just how much the shrinkage of
gum is affected by the temperature and drying rate is not known at
present. There is no doubt that the method of seasoning affects the
shrinkage of the gums, however. It is just possible that these woods
may shrink longitudinally more than is normal, thus furnishing another
cause for their peculiar action under certain circumstances. It has
been found that the properties of wood which affect the seasoning of
the gums are, in the order of their importance: (1) The indeterminate
and erratic grain; (2) the uneven shrinkage with the resultant
opposing stresses; (3) the plasticity under high temperature while
moist; and (4) the slight apparent lack of cohesion between the
fibres. The first, second, and fourth properties are clearly
detrimental, while the third may possibly be an advantage in reducing
checking and "case-hardening."

The grain of the wood is a prominent factor also affecting the
problem. It is this factor, coupled with uneven shrinkage, which is
probably responsible, to a large extent, for the action of the gums in
drying. The grain may be said to be more or less indeterminate. It is
usually spiral, and the spiral may reverse from year to year of the
tree's growth. When a board in which this condition e