more apparent, more
lasting, and of more consequence to the architect, builder, or owner
than the slight expansion which takes place, as, although the amount
of moisture contained in wood varies with the climate conditions, the
consequence of dampness or moisture on good timber used in houses only
makes itself apparent by the occasional jamming of a door or window in
wet or damp weather.

Considerable expansion, however, takes place in the wood-paving of
streets, and when this form of paving was in its infancy much trouble
occurred owing to all allowances not having been made for this
contingency, the trouble being doubtless increased owing to the blocks
not being properly seasoned; curbing was lifted or pushed out of line
and gully grids were broken by this action. As a rule in street paving
a space of one or two inches wide is now left next to the curb, which
is filled with sand or some soft material, so that the blocks may
expand longitudinally without injuring the contour or affecting the
curbs. But even with this arrangement it is not at all unusual for an
inch or more to have to be cut off paving blocks parallel to the
channels some time after the paving has been laid, owing to the
expansion of the wood exceeding the amounts allowed.

Considerable variation occurs in the expansion of wood blocks, and it
is noticeable in the hardwoods as well as in the softwoods, and is
often greater in the former than in the latter.

Expansion takes place in the direction of the length of the blocks as
they are laid across the street, and causes no trouble in the other
direction, the reason being that the lengthway of a block of wood is
across the grain, of the timber, and it expands or contracts as a
plank does. On one occasion, in a roadway forty feet wide, expansion
occurred until it amounted to four inches on each side, or eight
inches in all. This continual expansion and contraction is doubtless
the cause of a considerable amount of wood street-paving bulging and
becoming filled with ridges and depressions.

Elimination of Stain and Mildew

A great many manufacturers, and particularly those located in the
Southern States, experience a great amount of difficulty in their
timber becoming stained and mildewed. This is particularly true with
gum wood, as it will frequently stain and mould in twenty-four hours,
and they have experienced so much of this trouble that they have, in a
great many instances,