Page:Cassells' Carpentry and Joinery.djvu/47

 parts. McNeile's process is said to be very good: the wood to be seasoned is exposed to a moderate heat in a moist atmosphere charged with the products of combustion, say CO2, which is supposed to convert the sap to woody fibre and drive out the moisture. Smoke-drying over an open wood

Fig. 129.—Four-chamber "Sturtevant" Drying Kiln, Section.

fire drives out the sap and moisture and renders the wood more durable and less liable to attack by worms. Burying logs in sand is a method of artificial seasoning. The disadvantage of artificial seasoning is that the method of drying is too rapid, and seems to take away the stability of the material, leaving it less firm, more brittle, and duller in appearance.

Modern Method of Artificially Seasoning Timber.

Nature seasoning takes so long that it keeps idle a vast amount of capital. By artificial means timber can be dried in fewer days than it takes months by the natural process, consequently improvements in the methods of seasoning are constantly being sought for. A large quantity of deals, battens, planks, etc., receive a first seasoning before being placed on the market. The most effective artificial methods of seasoning are probably of American origin. The following two systems are largely in use.