Wood is an article of universal application; its lightness, strength,
and the facility with which it can be worked, render it almost
invaluable; although in ship-building and many of its applications
to house-building iron has to some extent superseded it, yet there
are so many other ways in which it is indispensable, that it may
be looked upon as one of the greatest boons to mankind. There is
scarcely a use to which wood may not be applied, whether as fuel
for fires, timber for building, furniture both useful and ornamental,
various parts of machinery, vessels to contain wine and other fluids,
handles to instruments, (for in cold climates and cold weather metal
cannot be handled with impunity), and indeed for all uses in which
lightness, dryness, warmth, and variety of form are desirable, wood
serves as an excellent material. The kind of trees that produce wood
fit for building and other useful purposes are those called by the
botanists _exogenous_. Amongst which the pine tribe, oak, ash, elm,
and beech, stand pre-eminent; while mahogany, walnut, and rosewood
are chiefly used for ornamental purposes; box-tree wood is also very
useful on account of its closeness and evenness of grain; it is the
wood used by engravers.
Wood when first cut is wet and heavy, but, by being exposed to the
air, it shrinks and the sap dries up in it, it is therefore liable to
swell and become damp in moist situations this is detrimental to its
usefulness; most woods therefore are improved by being soaked a long
time in water, this cleanses it from saline and extractive matters
which keeps the wood damp, but which, when separated, allow the wood
to shrink and harden permanently, this process is called seasoning,
the same effect may be produced by exposure to the air and rain,
it is generally resorted to when the timber is cut up into smaller
pieces. The structure of wood is porous, hence its lightness, it has
also a grain which runs the whole length of the wood in circles round
its centre to the surface, one of these circles is produced every
year while the tree is growing; wood is therefore capable of being
cleft in the direction of the grain by a wedge, in this way builder’s
laths are made. Wood cannot be cleft across the grain, but must be
cut by sawing or otherwise. The pine or fir tribe produce the largest
and straightest timber, but it is not so strong nor so durable as oak
and many other woods.
Some specimens of the _Araucaria Excelsa_ or Norfolk Island pine,
have stems upwards of three hundred feet high, and in the Crystal
Palace is the bark of another gigantic tree the _Wellingtonia
Gigantea_.