Wood when first cut is wet and heavy, but, by being exposed to the air, it shrinks and the sap dries up in it, it is therefore liable to swell and become damp in moist situations this is detrimental to its usefulness; most woods therefore are improved by being soaked a long time in water, this cleanses it from saline and extractive matters which keeps the wood damp, but which, when separated, allow the wood to shrink and harden permanently, this process is called seasoning, the same effect may be produced by exposure to the air and rain, it is generally resorted to when the timber is cut up into smaller pieces. The structure of wood is porous, hence its lightness, it has also a grain which runs the whole length of the wood in circles round its centre to the surface, one of these circles is produced every year while the tree is growing; wood is therefore capable of being cleft in the direction of the grain by a wedge, in this way builder’s laths are made. Wood cannot be cleft across the grain, but must be cut by sawing or otherwise. The pine or fir tribe produce the largest and straightest timber, but it is not so strong nor so durable as oak and many other woods. Some specimens of the _Araucaria Excelsa_ or Norfolk Island pine, have stems upwards of three hundred feet high, and in the Crystal Palace is the bark of another gigantic tree the _Wellingtonia Gigantea_. COTTON. Illustration: COTTON (‡ PLANT). Cotton consists of the fine long hairs which grow from the seeds of several varieties of _Gossypium_, a plant belonging to the natural order of _Malvaceæ_. These hairs are so long and numerous that they completely fill the pod or seed vessel; they are very delicate, and of the same size throughout, and but seldom jointed, they are each separate from the other. The cotton plant is chiefly cultivated in America and India. In India, and some of the islands in the Indian Ocean, cotton has been cultivated, spun, and woven into textures from time immemorial. Cotton fabrics were in use in Mexico before its conquest by the Spaniards, and have been used in China for many hundred years; its chief source now is America, where more than two hundred times the quantity is grown at present than was grown there half-a-century ago; but the internal communication brought about by railways in India, may, in all probability, revive the cultivation of cotton in that country; the cost of conveyance from the interior having been one of the greatest drawbacks to its exportation.