Smoke drying in an open chamber, or the burning of furze, fern, shavings, or straw under the wood, is said to give it hardness and durability; and, by rendering it bitter, destroys and prevents worms. It also destroys the germ of any fungus which may have commenced. It is an old and well-founded observation that smoke drying contributes much to the hardness and durability of woods. Virgil appears to have been aware of its utility, when he wrote the passage which is thus translated by Dryden: “Of beech, the plough-tail, and the bending yoke, Or softer linden, hardened in the smoke.”--GEORGICS, i., 225. Beckman, in his ‘History of Inventions,’ quotes a passage from Hesiod to the same effect; and adds, “as the houses of the ancients were so smoky, it may be easily comprehended how, by means of smoke, they could dry and harden pieces of timber.” In this manner were prepared the pieces of wood destined for ploughs, waggons, and the rudders of vessels: “These long suspend, where smoke their strength explores, And seasons into use, and binds their pores.”--VIRGIL. The late Brigadier-General Sir Samuel Bentham bestowed much time and attention in endeavouring to ascertain the quickest and best means of drying oak. In his letter to the Navy Board, 6th March, 1812, he says: “By exposing block shells to the smoke of burning wood, they become in the course of two or three days well seasoned in every respect, hard, bright coloured, and, as it were, polished. But it was found in a very short time that the acid with which the shells were thus impregnated very rapidly corroded the iron pins which passed through them. “In Russia many small articles, such as parts of wheels, wheel carriages, and sledges, are prepared in this manner; so are wheels, at least in some parts of America; and sabots and other small articles in France.” In speaking of artificial heat, he says, in the same letter: “From all the opportunities I have had of examining the state of timber so prepared by artificial heat, the due seasoning without cracking has appeared to depend on the ventilation happening to be _constant_, but very _slow_, joined to such a due regulation of the heat as that the _interior_ of the timber should dry, and keep pace in its contraction with the outer circles.” Mr. T. W. Silloway, in ‘American Carpentry,’ remarks: “If timber be dried by heat, the outside will become hardened, and the pores closed, so that moisture, instead of passing out, will be retained within.”