SOME COMMON CONIFERS AND THEIR TIMBERS 29
The Douglas Fir (Pseudotsuga taxifolia (Poir.) Britt.) produces
the most important building timber in the British Empire. In
its native haunts in Western North America the tree may attain
immense sizes, exceeding 300 feet in height and 12 feet in diameter.
Some idea of what such heights mean is obtained from a view of
the flagpole in Kew Gardens, a single spar of Douglas fir 214
feet long. Timbers from this tree can be obtained 80 feet long
and 30 inches square, and of course the wood is in demand for
heavy constructional work like bridge building and wharf and
pier construction. Otherwise the wood, which is also called
Oregon and Columbian pine, is used for much the same purposes
as red deal, being in demand for paving blocks, sleepers, flooring
and general constructional work. It is not quite so durable as
the timber of Scots pine; moreover, it is not an easy wood to
creosote effectively. Douglas fir, in the form of plywood, is
also used for panelling; the spring growth contrasts sharply
with the summer wood, and there is thus produced, on plain
sawn timber (the so-called slash grain) a somewhat garish figure
which some find attractive. The dense summer wood absorbs
more water than the soft spring wood and thus tends to swell
more; when this happens the "grain" is said to "lift," for
some purposes an undesirable property, for it will show through
several coats of paint under suitable conditions. This sharp
difference between spring and summer wood has made possible
a technique by which the wood is sand-blasted, a process which
wears away the softer spring wood more rapidly than the summer
wood, producing an attractive "water-worn" type of finish
very suitable for panelling.
In Britain Douglas fir grows very rapidly and yields a
coarse timber with wide growth rings, certainly a poor substitute
for the imported wood. However, the rate of growth decreases
as the tree gets older and thus wood of finer texture and, usually,
higher quality is produced.
Among other forest giants of the western forests of North
America are the Sequoias, of which the Californian Big Tree or
Wellingtonia (Sequoia Wellingtonia Seem.) is more commonly
seen in Britain. Its timber is similar to that of the redwood
and may be used for the same purposes, but, being more brittle,
it is of course of less value. The Californian Redwood (Sequoia
sempervirens (Lamb.) Endl.) produces a wood of a rich cold
brown colour, with a yellowish white sapwood: it is rather
soft and light, but has many uses. It is valued for outdoor
work, being remarkably durable and, by a strange irony, a very
easy wood to preserve. It is a nice wood for joinery, and its
value is enhanced for this purpose by reason of its small shrinkage.
The timber is resistant to acids and is in demand for the manu-