Page:Cassells' Carpentry and Joinery.djvu/64

48 of its strongly marked and handsome grain; for open timber roofs on account of its strength and appearance; and for outdoor carpentry, such as jetties, on account of its length and size. The ornamental grain of pitchpine is due to the annual rings, not the medullary rays as in oak. and the method of sawing oak will therefore not suit at all. The object should be to cut as many boards as possible tangent to the annual rings. About one log in a hundred will show more or less waviness of the grain owing to an irregular growth in the tree, and about one in a thousand will be worth very careful conversion. To avoid turning the log so often in cutting the boards, as in Fig. 137 (p. 35), they might be all cut parallel, so obtaining a greater number of wide boards but not of such good figure, the grain showing straight lines towards the edges instead of a fair pattern throughout. Careful and complete seasoning would be required, on account of the great shrinkage occurring.

Oak. — English oak (Quercus) is of a light brown or brownish yellow, close-grained, tough, more irregular in its growth than other varieties, and heavier. Its tenacity is, say, 6½ tons per square inch, and its weight, 55 lb. per cubic foot. Baltic oak from Dantzic or Riga is rather darker in colour, close-grained, and compact, and its weight is 49 lb. per cubic foot. Riga oak has more flower than Dantzic. American or Quebec oak is a reddish brown, with a coarser grain, not so strong or durable as English oak, but straighter in the grain. Its tenacity is 4 tons per square inch, and weight 53 lb. per cubic foot. African oak is not a true oak. Exposed to the weather, oak changes from a light brown or reddish grey to an ashen grey, and becomes striated from the softer parts decaying before the harder. In presence of iron it is blackened by moisture owing to the formation of tannate of iron, or ordinary black ink.

Wainscot Oak. — This, known also as "Dutch wainscot," is a variety of oak. It has a straight grain free from knots, is easily worked, and not liable to warp. In conversion it is cut to show the flower or sectional plates of medullary rays. It is used for partitions, dados, and wall panelling generally; also for doors and windows in high-class joinery. Its sources are Holland and Riga, being imported in semi-circular logs. Wainscot oak obtained from Riga is spoken of as Riga wainscot. The term "wainscot" describes the method that is adopted, when converting the log into boards, in order to show a large amount of silver grain; such ornamental boards are specially suitable for wainscoting. The oaks that grow around the Baltic are closely related to those that grow in England. Quercus robur affords the best timber as regards strength and durability under exposure, though some of the other varieties (as, for instance, the Quercus sessiliflora, or cluster-fruited oak) have an equally pretty figure. Riga oak is not held in such high esteem as English oak for outdoor work and for purposes in which great tensile or compressional strength is necessary; but as the medullary rays are very prominent, Riga oak affords a very pretty silver grain. Riga oak may be the wood of either of the two varieties of Quercus mentioned above.

Chestnut. — The chestnut timber used for building is the sweet or Spanish chestnut (Castanea edibilis), not the common horse chestnut, which is a whitish wood of but little use. The Spanish chestnut is grown only to a small extent in Great Britain at the present time; it may be known by the leaves being smoother, more parallel, and not radiating so decidedly from one stalk. Spanish chestnut closely resembles coarse-grained oak in colour and in texture, and the wood in all its stages of manufacture is frequently mistaken for oak. The bark of the log is like oak bark. The planks are of practically identical appearance, and even after the wood is dressed up the likeness is still very close. However, when the chestnut is old it has rather more of a cinnamon cast of colour, has less sapwood, and generally a closer grain, although softer and not so heavy as oak. The chief distinguishing characteristic of the chestnut is the absence of the distinct medullary rays which produce the flower in oak; and old roof-timbers, benches, and church-fittings may be discriminated in this way, also by the chestnut being more liable to split in nailing, while the nails never blacken the