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.