543. The Austrian oak is another variety of the European species, but of which the author has not been able to determine. The tree is taller than the English oak, and the wood is whiter, softer, and less durable.

544. Of the American species the Chestnut-leaved Oak (Q. prinos) is a tall tree, remarkable for the beauty of its form. The wood of some varieties is coarse-grained, but very serviceable and much used for wheel-carriages in America.

545. The Red Oak (Q. rubra) is a native of Canada and the country west of the Allegany Mountains. It is called the red oak from the leaves changing to a red or purple colour before they fall off. It is a large and fine tree of 90 or 100 feet in height, and of rapid growth. The wood is used for staves and other purposes, but is light, spongy, and not very durable.

546. White Oak (Q. alba), so called from the whiteness of its bark, is a native of the woods from Canada to Carolina, and grows to an immense size in some of the middle states, often attaining the height of 70 or 80 feet, with a trunk from 5 to 7 feet in diameter.

The timber of the white oak has a whitish-brown colour, with a reddish tinge, is tough and pliable, and is preferred to all other kinds in America for both house and ship carpentry, being the most durable of any. The wood is less durable, however, than the British oak, but is of a quicker growth and of straighter grain.

The white oak is not suitable for boards, as it shrinks about 1/32 part in seasoning, and is very subject to warp and crack.

It is the timber of this 6pccies that is exported from Canada to Europe under the name of "American Oak."

547. The Iron Oak, or post oak (Q. obtusiluba) is another American species that produces valuable timber. It is found most abundantly in the forests of Maryland, and Virginia, where it is frequently called "Box White Oak," but is rarely seen farther north than the mouth of the Hudson River.

The tree seldom attains a greater diameter than about 15 inches, and on this account is chiefly used for posts and fencing. The wood has a yellowish hue and close grain, and is said to exceed the white oak in strength and durability. It sometimes attains a height of 50 or 60 feet.

548. The Live Oak (Q. virens). This is considered the best of the American kinds for ship-building. The tree grows, in the southern states of America, to a height of 40 or 50 feet, with wide-spreading branches, and a trunk of from 12 to 24 inches in diameter. It is rarely found farther north than the neighbourhood of Norfolk, Virginia, nor farther inland than from 15 to 20 miles from the sea-coast; but it is found in abundance along the coast southwards as far as the mouth of the Mississippi. The wood has a yellowish tinge, is heavy, compact, and of fine grain. It is stronger and more durable than any other species, and is considered invaluable for the purpose of ship-building, for which it is exclusively reserved. Mr. Knowles states that out of 507 pieces which had been in the ' Essex ' frigate for twelve years, only six were found to be defective.

549. According to Hassenfratz, the mean size of the trunk of the

550. Oak of a good quality is more durable than any other wood that attains a like size. Vitruvius says, it is of eternal duration when driven into the earth; and it is well known to be extremely durable in water; and in a dry state it has been known to last nearly 1000 years. The more compact it is, and the smaller the pores are, the longer it will last; but an open porous and foxy-coloured oak, which grows in some parts of Lincolnshire, is not near so durable. Chapman very justly observes that the heart of such oak is scarcely superior to the sap of better kinds.

The chief use of oak before the introduction of iron was for ship-building, which consumed enormous quantities. In 1788 more than 50,000 loads of timber were required for the construction and repair of the British Navy.*

It is useful for many purposes besides ship-building, particularly in situations where it is exposed to the weather. It makes the best wall-plates, ties, templets, king posts, and indeed it is best suited for every purpose where its warping in drying and its flexibility do not render it objectionable; but, as Vitruvius has observed, it is very liable to twist and cause cracks in the work in which it is employed.

The colour of the oak is a fine brown, and is familiar to everyone: it is of different shades; that inclined to red is the most inferior kind of wood. The larger medullary rays are in general very distinct, producing beautiful flowers when cut obliquely. Where the rays are small and not very distinct the wood is much the strongest. The texture is alternately compact and porous, the compact part of the annual ring being of the darkest colour, and in irregular dots, surrounded by open pores, producing beautiful dark veins in some kinds, particularly in pollard oaks.

It has a peculiar smell, and the taste is slightly astringent. It contains gallic acid, and is blackened by contact with iron when it is damp.

The young wood of English oak is very tough, often cross-grained; and difficult to work. Foreign wood and that of old trees arc more brittle and workable.

Oak warps and twists much in drying, and shrinks about one-thirty-second part of its width in seasoning, according to Mr. Couch's experiments.

The cohesive force of oak varies from 7850 to 17,892 lbs.

* ' Report of Commissbioners of Woods and Forests for 1812.' per square inch. The mean of Barlow's experiments is 10,000 lbs. 11,880 has been taken in this work as a standard to compare with the other woods, being the result of an experiment on a specimen of a mean quality.

The weight of a modulus of elasticity for a square inch is 1,714,500 lbs., from a mean of various specimens.

The weight of a cubic foot of different kinds of oak is as under: -

Representing the strength, stiffness, and toughness of the common English oak (Q. pedunculata) each by 100, it may be compared with the other kinds as under: -

It is necessary to observe, that the specimens of Riga and Dantzic oak were of the best quality.

Division I. (continued).

551. Sub-Div. II

Annual rings not distinct; texture ' nearly uniform.