When timber is felled, the sooner it is removed from the forest the better; it should be removed to a dry situation, and placed so that the air may circulate freely around each piece, but it should not be exposed to the sun and wind. Squared timber does not rift or split so much as that which is round. After the trees have been allowed to dry slowly, and where the size will allow of it, it is better to quarter them. When beams are to be used the full size of the tree, it would be a good preservative against splitting to bore them through from end to end, as is done in a water-pipe. It is irregular drying which causes timber to split, and this method would assist in drying the internal part of the beam, without causing much loss of strength, at the same time it would lighten the beam considerably. " Ancient architects," says Alberti, "not only prevented the access of the scorching rays of the sun and the rude blasts of wind, but also covered the surface with cow-dung to prevent the too sudden evaporation from the surface." *

* 'Vitruvius,' book ii., chap. ix.

† ' Encyclopaedia Britannica,' art. Dry Rot.

Duhamel has shown that it is a great advantage to set the timber upright, with the lower end raised a little from the ground;† but as this cannot always be done, the timber-yards should be well drained, and kept as dry as possible. Paved yards are to be preferred, and the paving should have a considerable fall, to prevent water standing. If the paving were laid with ashes it would be better; those from a forge or foundry would be excellent: even an unpaved yard would be improved by a coat of ashes, to prevent anything growing among the timber.

If timber can be kept some time in a dry situation before it is cut into scantlings, it will be less subject to warp and twist in drying; but during the time it is kept in the tree or log it should be carefully piled, so as to leave space for a free circulation of air between each piece, and also between the timbers and paving or ground. Lately, in some of the Government yards, the timber has been laid upon cast-iron bearers, instead of being laid upon refuse pieces of wood; as the refuse wood is often half rotten, and must in some degree contribute to infect the sound timber. Timber is too often suffered to lie half buried in the ground, or grown over with weeds, until it is covered with fungus, and impregnated with the seeds of decay before it is brought into use.

* Book ii., chap, v † ' Transport des Bois,' p. 238.

When it is necessary to convert the timber into smaller scantlings, it still requires attention; as the better it is seasoned, when brought into work, the better the work will stand; it will also be more durable. The experiments of Duhamel show that such scantlings will dry soonest in an upright position, and that the upper end dries more rapidly than the lower one.* But whether the pieces of timber be piled on the end, or laid horizontally, a free space should be left round each, and the situation should be dry and airy; they should not be exposed to the direct rays of the sun, nor to a strong current of air. If the pieces be laid horizontally, short blocks should be put between them, which will preserve them from becoming mouldy, and will contribute much towards rendering the sappy parts more durable.

Gradual drying, where the time can be allowed for it in the natural process, is the most certain means of giving durability to timber, by fixing those parts of it which are most liable to be acted upon by heat and moisture.

It is well known to chemists that slow drying will render many bodies less easy to dissolve, while rapid drying, on the contrary, renders the same bodies more soluble; besides, all wood in drying loses a portion of its carbon, and the more in proportion as the temperature is higher. There is, in wood that has been properly seasoned, a toughness and elasticity which is not to be found in rapidly-dried wood. This is an evident proof that firm cohesion does not take place when the moisture is dissipated in a high heat. Also, that seasoning by heat alone, produces a hard crust on the surface, which will scarcely permit the moisture to evaporate from the internal part, and is very injurious to the wood.

* 'Transport des Bois,' p. 83.

For the general purposes of carpentry, timber should not be used in less than two years after it is felled; and this is the least time that ought to be allowed for seasoning. For joiners' work it requires four years, unless other methods be used; but for carpentry natural seasoning should have the preference, unless the pressure of the air be removed.

Duhamel says that the quantity of matter which ought to be evaporated from green oak is about one-third or two-fifths of its weight; the proportion, however, will vary according to the age and quality of the timber, and the nature of the soil that produced it.* The time required to dry a piece of timber will depend on the scantling and on the surface exposed to the action of the air.

Equal drying should be promoted by frequently turning the pieces, and by keeping them free from the ground or other damp situations.

The evaporation is greater from the ends of a piece of timber than from the sides, and greater from the upper than from the lower side.

There are two states in which timber is used in building, viz. when it is dry, and when it is only seasoned. The latter term has not been very accurately defined. Rondelet considers timber to be sufficiently seasoned for carpenters' work when it has lost about one-sixth of its weight. According to the author's own observations, timber has undergone what is termed a proper seasoning for common uses when it has lost about one-fifth of its weight; therefore we shall call that timber seasoned which has lost one-fifth of the weight it had at the time of felling.

It also appears from the experiments of Duhamel † and

* ' Transport des Bois,' p. 72. † ' Transport des Bois.'

Couch,* that timber loses about one-third of its weight in becoming dry; and such a degree of dryness being sufficient for the joiner's purpose, we shall consider timber dry when it has lost one-third of its weight.

Thus the terms dry and seasoned will have a more certain meaning; and when drying is carried to its greatest extent, the timber may be called perfectly dry, to distinguish it from that degree of dryness which renders it fit for framing and joiners' work.