The common acacia is very durable; it is equal or superior to oak in stilthess and toughness, and is very valuable for fencing. The colour is a greenish yellow, with a slight tinge of red in the pores, and is, in structure, alternately compact and very porous, so that the rings are very distinct ; it has no large septa.
There are several species of poplars, of which the Lom ba•dy, black, and conunon white, are mostly esteemed. They are all very durable when preserved in a dry state; and the aspen or trembling poplar will last a considerable time ex posed to the weather. They are not well adapted for largo timbers, but are well fitted for flooring, where there is no great wear, they do not take fire readily.
The colour is of a yellowish or brownish white, one side of the annual rings being a little darker than the other. The wood is of a uniform texture, and has no large septa.
Red or yellow fir is the produce of the Scotch fir, and is common in the north of Europe,in Scotland,liussia,llenmark, Sweden, Norway, and Lapland. It is very durable ; and its lightness and st iffiless render it superior to any other material for beams, girders, joists, rafters, and framing in general. It is also much used for joiners' work, both external and in ternal, being cheaper and more readily worked than oak. The wood from cold climates is stronger than that from warmer situations. The colour is of a reddish or honey yellow, and of various degrees of brightness; the layers are well marked, the one part being soft and light-coloured, the other hard and dark : in the best timber the rings are thin, not more than of an inch in thickness. The inferior kinds have thick annual rings; in some kinds the dark parts of the rings are of a honey-yellow, the wood, heavy, and filled with soft resinous matter, feels clammy, and chokes the saw. In other inferior kinds it is spongy, contains less resinous matter, and leaves a woolly surface after the saw.
White fir, or deal, is the produce of different varieties of spruce fir, and is imported from the north of Europe, and from America. Of Norway spruce, a great quantity is im ported from Christiana in deals and planks, which are very highly esteemed. The American wood is not so resinous as that from Norway ; it is tougher, less heavy, and generally more liable to twist in drying. it is of two kinds, white and black spruce, the latter producing the best wood. White deal is very durable in a dry state, and is much used tbr internal joiners' work.
The colour is yellowish or brownish white ; the hard part of the annual ring a darker shade of the same colour, often has a silky lustre, especially in the American and British grown kinds. Each annual ring consists of two parts, the one hard and the other softer. The knots are generally very
hard. The clear and straight-grained kinds are often tough, but not very difficult to work, and stand extremely well when properly seasoned.
The Weymouth, or white pine, is a native of North America, and is imported in large logs, often more than 2 feet square, and 30 in length : it is one of the largest and most useful of the American pines. The wood is light and soft, and is said to stand the weather tolerably well. in joinery it is much used for mouldings and 'other work, where clean straight-grained wood is desirable; but it is not durable, nor lit for large timbers, being very liable to take the dry-rot. The colour is brownish yellow, and the texture more nearly uniform than that of any other of the pine species, and the annual rings not very distinct.
The pitch pine is a native of Canada. It is very resinous and heavy,.but not very durable: it is also brittle when very dry. It is of a redder colour than the Scotch pine, feels sticky, and is difficult to plane.
The silver fir is a native of the mountains of Siberia, Ger many, and Switzerland, and is common in British planta tions. The wood is of a good quality, and much used on the continent both for carpentry and shipbuilding. The harder fibres are of a yellow colour, compact and resinous ; the softer nearly white. it is light and stiff, and does not bend much under a considerable load ; consequently floors constructed of it remain permanently level. It is subject to worm.
Of the larch there are three species ; one European, and two American. The wood is extremely durable in all situ ations,even when exposed to damp and weather ; it is adapted for both internal and external work, and especially for floor ing boards, which are subject to much wear ; also for doors, shutters, &c.
The wood of the European larch is generally of a honey yellow colour, the hard part of the annual rings of a redder cast; sometimes it is brownish white. In common with the other species of pine, each annual ring consists of a hard and soft part. It generally has a silky lustre, and its colour is browner than that of the Scotch pine, and it is much tougher. It is more difficult to work than Riga or Memel timber, but the surface is better when once it is attained. It bears driv ing bolts and nails better than any other kind of resinous woods. When it has become perfectly dry it stands well, but warps much in seasoning.
The following table, showing the comparative strength, stiffness, and toughness of various woods, taking English oak at 100 as a standard, is compiled from Tredgold, from whose work the above observations are principally extracted :— For further information on this head, see STRENGTH OF MATERIALS.