Dr. Darwin is of opinion, that the dry-rot may be entirely pre-vented, by soaking the timber first in lime-water, till it has absorbed as much of it as possible, and, after it has become dry, immersing it in a weak solution of vitriolic acid in water, which he supposes will not only preserve it from decay for many centuries (if it be kept dry), but also render it less inflammable ; a circumstance that merits considerable attention in construct-ing houses.
In the Transactions of the Society for the Encouragement of Arts, we meet with the following account of the cause of the dry-rot in timber, and the method of preventing it, communicated by Robert Batson, of Limehouse, Esq. - He observes, that the dry-rot baa tag taken place in one of his parlours, to such a degree as to require the pulling down part of the wainscot, every third year; and perceiving that it arose from a damp stagnated air, and from the moisture of the earth, he deter-mined, in the month of June, 1783, to build a narrow closet, next the wall through which the moisture came to the parlour: this expedient had the desired effect. But, though the rot in the parlour was totally stopped, the evil soon appeared in the closet, where fungi of a yellow colour arose in various parts. In the autumn of the year 1786, .the closet was locked up about ten weeks: on opening it, numerous excrescences were ob-served about the lower part; a white mould was spread by a plant resembling a vine or sea-weed; and the whole of the inside, china, was covered with a fine powder of the colour of brick-dust. On cleaning out the closet, it was discovered that the disease had af-fected the wood so far as to extend through every shelf, and the brackets that supported them. In the beginning of the year 1787, he determined to strip the whole closet of lining and floor, not to leave a particle of the wood behind, and also to dig, and take away, about two feet of the earth in depth, and leave the walls to dry, so as to destroy the roots or seeds of the evil. When, by time, the admission of air, and good brushing, it had become properly dry and cleansed, he filled it of sufficient height for the joists, with anchor-smith's ashes ; because no vegetable will grow in them. The joists being sawed off to their proper lengths, and fully prepared, they and the plates were well charred, and laid upon the ashes; particular directions being given, that no scantling or board might be cut or planed in the place, lest any dust or shavings might drop among the ashes. The flooring-boards being very dry, he caused them to be laid close, to prevent the dust getting down, which perhaps, in the course of time, might bring on vegetation. The framing of the closet was then fixed up, having all the lower pan-nels let in, to be fastened with but-tons only, so that, if any vegetation should arise, the pannels might with ease be taken out, and examined.
In some situations, it might be expedient and necessary to take out a greater depth of earth ; and where ashes can be: had from a foun-dery, they may be substituted for those of anchor-smiths; but houseashes are by no means to be de-pended upon.
At the expiration of seven years from the period of making this experiment, the wainscot was removed, and the flooring - boards also taken up, when they were found entirely free from any appearance of the rot: two pieces of wood (yellow fir) which had been driven into the wall as plugs, without being previously charred, were alone affected with this disease.