It is an old and a well-founded observation, that smoke-drying contributes much to the hardness and durability of wood. Virgil seems 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 harden'd in the smoke." *

Georgics, I., 225.

But this method can only be effectually applied on a very small scale; yet sometimes, for particular purposes, it may be useful to season in the smoke. As a substitute for the smoke of an open chimney, Ellis advises to burn fern, furze, straw, or shavings under the timber,† which would destroy any seeds of fungi or worms, and so embitter the external surface as to prevent any further ill-effect from either. It would be easy to contrive the means of smoke-drying for the use of a manufactory where much seasoned wood was used.

Scorching must do timber much harm when done hastily, as it causes rents and cracks, which become receptacles for moisture, and consequently cause rapid decay.

It must always be remembered that charring the surface is only useful in as far as it destroys and prevents infection; and that its application should be confined to timber already seasoned; for when applied to green timber, it closes up the pores at the surface, so that the internal sap and moisture cannot evaporate.

* Becktnan (in his ' History of Inventions,' vol. ii., p. 77) 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 pices 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.'

Sotheby's Virgil.

† ' Timber Tree Improved,' by Mr. Ellis.

In that kind of decay which arises from the constant evaporation of moisture, charring the surface produces no effect. Duhamel made some experiments on this point, and found that there was very little difference between the posts he had charred, and those he had not charred, at the end of six years;* but as a preventive of infection by the dry rot, and of the worm in timber, charring appears to be very beneficial, and will no doubt be assisted by impregnating the timber with the bitter particles of smoke.