Page:EB1911 - Volume 26.djvu/1020

 annual rings being of a darker shade. A characteristic feature is the large number of very hard black knots which the wood contains. It is easy to work, but rather inferior in all respects to the northern pine. Its weight per cubic foot averages about.

The red pine (Pinus resinosa or P. rubra) is also known as “Canadian pine” and “American deal.” It grows in the northern parts of North America, where the tree attains a height of 60 or 70 ft. with a diameter of from 12 to 30 in. It weighs about to the cubic foot. In Canada it is called “Norway pine” and “red pine” from the colour of the bark. The wood is white, tinged with yellow or red, of fine grain, and works to a smooth lustrous surface remarkably free from knots.

The white pine (Pinus strobus) is exported from the northern parts of the United States of America and from Canada. Other names for this timber are “yellow pine” and “Weymouth pine,” the last name originating in the fact that the earl of Weymouth first introduced it into England. The tree attains a height of from 150 to 200 ft. with a thickness of trunk at 5 ft. from the bottom of from 5 to 10 ft. The wood when cut is white or yellowish white, straight in grain and easily worked, but is not so tough, elastic or durable as the northern pine, and therefore is not so suitable for constructional work. For joiners' work, however, it is well adapted, and glue adheres strongly to it, though nails do not hold well. It weighs about 30 ft per cub. ft.

The Kauri pine (Dammara australis) is a native of New Zealand. It grows to a height of from 80 to 140 ft., with a straight stem 4 to 8 ft. in diameter. The wood is a light yellowish brown in colour, fine in grain and of even texture, the annular rings being marked by a darker line. It is strong, elastic and resinous. A cubic foot weighs about 35 to.

The pitch pine (Pinus rigida) is a native of Canada and is common throughout the United States of America. It is remarkable for the large quantity of resin it contains, the weight of the wood, which is about per cub. ft., and the strong red markings of the grain, usually straight but sometimes exhibiting a beautiful figure. Its weight and strength, and the large size of the balks, make it very valuable for heavy constructional works and piling, and its fine figure makes it equally valuable for joinery.

Of the larch the best known variety is the European larch (Larix europaea), which grows in Switzerland, Italy, Russia and Germany. The larch frequently attains a height of 100 ft. but the average height is about 50 ft. and diameter 3 ft. The wood is extremely durable and lasts well where exposed alternately to wet and dry ; indeed, the larch is useful for every purpose of building, internal and external. It is the hardest and toughest of the cone-bearing trees and weighs 30 to per cub. ft. ; it has a straight grain free from many knots; in colour it is of a rather deep yellow or brownish tint, with the hard portions of the annular rings marked in a darker red. The American black larch (Larix pendula) and the American red larch (Larix microcarpa) are native to North America. The latter tree is of comparatively little service. The black larch yields timber of good quality, nearly equal to that of the European tree.

The cedar used in building work is really a species of juniper. The Virginian red cedar (Juniperus virginiana) grows in the United States, Canada and the West Indies. The tree produces excellent timber, and is much used for furniture, its strong acrid taste driving away insects. It weighs about per cub. ft. The Bermuda cedar (Juniperus bermudiana) is used for internal joinery and is extremely durable.

Hard Woods.—The timbers in the second class are obtained from non-coniferous trees, containing no turpentine or resin, and are given the general name of hard woods. Their initial expense and the high cost of working preclude their general use, and they are consequently reserved to a great extent for specially heavy constructional work and ornamental finishing joinery.

The numerous tests of the strength of timber which have been made by various authorities from time to time vary so much, both as regards the conditions under which they were carried out and the results obtained, that great discretion is required in using them for any practical purpose. An important series of tests was made in 1883 and 1887 at Munich by Professor Johann Bauschinger. He reduced all the specimens submitted for test to a standard of moisture, the percentage selected being 15%. This was necessary on account of the great difference in strength found to exist between specimens cut from the same piece of timber but differing in the amount of moisture they contained.