We thus observe there are twice three successful patent

processes.

Any inventions which cannot be brought under these three classes have had a short life; at least, we think so.

The same remarks will apply to external applications for wood-for instance, coal-tar, one application, is more used for fencing than any other material.

We are much in want of a valuable series of experiments on the application of various chemicals on wood to resist burning to pieces; without causing it to rot speedily.

CHAPTER VI.

ON THE MEANS OF PREVENTING DRY ROT IN MODERN HOUSES; AND THE CAUSES OF THEIR DECAY.

ALTHOUGH writers on dry rot have generally deemed it a new disease, there is foundation to believe that it pervaded the British Navy in the reign of Charles II. "Dry rot received a little attention," so writes Sir John Barrow, "about the middle of the last century, at some period of Sir John Pringle's presidency of the Royal Society of London." As timber trees were, no doubt, subject to the same laws and conditions 500 years ago as they are at the present day, it is indeed extremely probable that if at that time unseasoned timber was used, and subjected to heat and moisture, dry rot made its appearance. We propose in this chapter to direct attention to the several causes of the decay of wood, which by proper building might be averted.

The necessity of proper ventilation round the timbers of a building has been repeatedly advised in this volume; for even timber which has been naturally seasoned is at all times disposed to resume, from a warm and stagnant atmosphere, the elements of decay. We cannot therefore agree with the following passage from Captain E. M. Shaw's book on 'Fire Surveys,' which is to be found at page 44:"Circulation of air should on no account be

permitted in any part of a building not exposed to view, especially under floors, or inside skirting boards, or wainscots." In the course of this chapter, the evil results from a want of a proper circulation of air will be shown.

In warm cellars, or any close confined situations, where the air is filled with vapour without a current to change it, dry rot proceeds with astonishing rapidity, and the timber work is destroyed in a very short time. The bread rooms of ships; behind the skirtings, and under the wooden floors, or the basement stories of houses, particularly in kitchens, or other rooms where there are constant fires; and, in general, in every place where wood is exposed to warmth and damp air, the dry rot will soon make its appearance.

All kinds of stoves are sure to increase the disease if moisture be present. The effect of heat is also evident from the rapid decay of ships in hot climates; and the warm moisture given out by particular cargoes is also very destructive. Hemp will, without being injuriously heated, emit a moist warm vapour: so will pepper (which will affect teak) and cotton. The ship 'Brothers,' built at Whitby, of green timber, proceeded to St. Petersburgh for a cargo of hemp. The next year it was found on examination that her timbers were rotten, and all the planking, except a thin external skin. It is also an important fact that rats very rarely make their appearance in dry places: under floors they are sometimes very destructive.

As rats will sometimes destroy the structural parts of wood framing, a few words about them may not be out of

used, the

place. If poisoned wheat, arsenic, &c., be creatures will simply eat the things and die under the floor, causing an intolerable stench. The best method is to make a small hole in a corner of the floor (unless they make it themselves) large enough to permit them to come up; the following course is then recommended:-Take oil of amber and ox-gall in equal parts; add to them oatmeal or flour sufficient to form a paste, which divide into little balls, and lay them in the middle of the infested apartment at night time. Surround the balls with a number of saucers filled with water-the smell of the oil is sure to attract the rats, they will greedily devour the balls, and becoming intolerably thirsty will drink till they die on the spot. They can be buried in the morning.

Building timber into new walls is often a cause of decay, as the lime and damp brickwork are active agents in producing putrefaction, particularly where the scrapings of roads are used, instead of sand, for mortar. Hence it is that bond timbers, wall plates, and the ends of girders, joists, and lintels are so frequently found in a state of decay. The ends of brestsummers are sometimes cased in sheet lead, zinc, or firebrick, as being impervious to moisture. The old builders used to bed the ends of girders and joists in loam instead of mortar, as directed in the Act of Parliament, 19 Car. II. c. 3, for rebuilding the City of London.

In Norway, all posts in contact with the earth are carefully wrapped round with flakes of birch bark for a few inches above and below the ground.

Timber that is to lie in mortar-as, for instance, the

ends of joists, door sills and frames of doors and windows, and the ends of girders-if pargeted over with hot pitch, will, it is said, be preserved from the effects of the lime. In taking down, some years since, in France, some portion of the ancient Château of the Roque d'Oudres, it was found that the extremities of the oak girders were perfectly preserved, although these timbers were supposed to have been in their places for upwards of 600 years. The whole of these extremities buried in the walls were completely wrapped round with plates of cork. When demolishing an ancient Benedictine church at Bayonne, it was found that the whole of the fir girders were entirely worm eaten and rotten, with the exception, however, of the bearings, which, as in the case just mentioned, were also completely wrapped round with plates of cork. These facts deserve consideration.

If any of our professional readers should wish to try cork for the ends of girders, they will do well to choose the Spanish cork, which is the best.

In this place it may not be amiss to point out the dangerous consequences of building walls so that their principal support depends on timber. The usual method of putting bond timber into walls is to lay it next the inside; this bond often decays, and, of course, leaves the walls resting only upon the external course or courses of brick; and fractures, bulges, or absolute failures are the natural consequences. This evil is in some degree avoided by placing the bond in the middle of the wall, so that there is brickwork on each side, and by not putting continued bond for nailing the battens to. We object to