Timber

(b) Felled Timber.—Tunnels or other cavities are also produced by animals in felled timber. In sea-water they result from attacks by Mollusca (e.g., shipworms) or small Crustacea (cf. shrimps), and on land are due to insects. Decay or rot of timber taking place in the standing tree or felled timber is always due to fungi (see DRY ROT), and is associated with discolouration and weakening of the wood but much less frequently with the pro duction of internal cavities.

Opposed to the shakes already considered are cross-shakes, which are cracks or splits running at right angles to the grain. In the overwhelming majority of cases they are due to decay of the wood, caused by fungi, and consequent shrinkage (see DRY ROT). They render wood useless for mechanical usage. But the logs of certain species of trees, including spruce, sabicu and some African mahoganies, occasionally show cross-shakes, even when there is no trace of decay.

For a discussion of Felling, forms and sizes

see LUMBERING. See also TIMBER PRESERVATION.

Special Sof twoods.

The name cedar is given to various un related, usually fragrant, softwoods and hardwoods. The true cedars (Cedrus) are familiar as trees of three kinds: the Hima layan deodar, the cedar of Lebanon and the Atlas Mountains cedar. Junipers (Juniperus) supply the pencil-wood cedar, the most important being the North American J. virginiana, though pencil slats are also made from another species growing in Kenya Colony: the heartwood is durable, as the scented cedar-wood oil is antiseptic and distasteful to insects. Lawson's cypress (Cha maecyparis Lawsoniana), indigenous in western United States, yields the valuable Port Orford cedar. Other North American cedar woods are produced by arbor vitae trees (Thuja), the durable red cedar wood (T. plicata) being used for shingles.

Bald, marsh or Louisiana cypress (Taxodium distichum) grows in swamps of south-eastern United States and Central America: its durable wood is unsurpassed for conservatories.

The European larch

(Larix decidua) is rather heavy and the red heartwood is very durable. The rather similar North Ameri can timbers are those of the tamarack (L. americana) and the western larch (L. occidentalis). Larch timbers find many of the same uses as hard-pines (see later).

Pine, true.—The name pine is given to a medley of softwoods, but should be restricted to timbers belonging to the genus Pinus. Such genuine pine-timbers may be ranged into two classes, hard pines and soft-pines, the former of which are generally heavier.

Hard-pines include one of the two most important softwoods of Europe, Baltic "red deal" (Pinus sylvestris, the Scots pine), which grows widely over Europe, and is represented in North America by a very similar timber, red or Norway pine (P. resinosa). The name pitch-pine as applied to North (and Central) American timbers in Great Britain and the United States, respec tively, is liable to cause confusion : in the latter country it refers to relatively poor wood of P. rigida, whereas in Great Britain and Europe it refers to pine-timbers of the highest class produced by P. palustris and two or three other species all exported from south-eastern United States to England.

Soft-pines include the timber of the American Weymouth pine (Pinus Strobus), which is known in England as "Canadian yellow pine" and in the United States as "Eastern white pine": it is not used out of doors, but for making matches, patterns and for high-class cabinet work.

Pines, so called.—A wide range of coniferous trees are known in Australasia as pines, and include the Kauri-pine (Agathis australis) of New Zealand, and Huon-pine (Dacrydiurn Frank linii) in Tasmania. The Oregon or British Columbian pine is Douglas fir (Pseudotsuga taxifolia) which grows in the Pacific States of North America.

Californian redwood (Sequoia sempervirens) has a reddish heartwood light in weight, very durable, and used for the manu facture of shingles and patterns.

White deal is the wood of the Norway spruce

(Picea excelsa) which is wide-spread over Europe. The white wood ranges in quality from the common grades used in packing cases, wood work of houses and pulp, to mountain-grown wood of the highest quality which provides the best sounding boards of pianos. To similar uses the black, white, red and Sitka spruces (Picea spp.) are put in North America. (See SPRUCE.) Special Hardwoods.—The ash-tree (Fraxinus excelsior) is widespread over Europe and supplies the timber of commerce, which is almost solely sap-wood, as any heart-wood is produced late in life. The wood is remarkably tough and, after steaming, can be permanently bent without losing its shock-resisting power. It is used in the manufacture of axe-handles, oars, bodies of carriages and motor-cars, hockey-sticks and so forth. In North America six species of Fraxinus supply commercial timbers.