1108 COTTAGE, FARM, AND VILLA ARCHITECTURE. their materials relatively to the centre of gravity, and on the stability and security of their foundations. The most durable of all walls are those built of brick with good mortar, because they attain a degree of homogeneousness which no construction of mortar and stone has ever yet equalled. The proof of this, is to be found in the ancient brick buildings of Italy. The walls next in durability arc those formed of fragments of porous stone, compactly bedded in good mortar or cement ; as in the remains of old Roman castles in Britain and in Germany. The third in order are those (commonly reckoned the first) which are composed of very large blocks of squared stone, and the strength of which does not at all depend on mortar or cements of any kind. 2188. To preserve Timber in Buildings from Decay, the most certain means are so to dispose it, as that it shall have efficient ventilation : but otlicr methods have also been employed. Among these are, steeping the timber, previously to use, in water, and after- wards drying it in the air ; subjecting it to the action of steam, and afterwards drying it; removing the atmospheric pressure, and at the same time applying artificial heat, so as to promote evaporation ; or steeping it in a solution of corrosive sublimate, which is now found the most efficient remedy, next to ventilation, for what is called the dry rot. The object of all these operations, except the last, is, to remove, by extraction and evapor- ation, what is called the sap, or the watery part of the alburnum, or last-formed layers of the wood, which are found to decay sooner than the interior and firmer, or less porous, layers ; and the object of the last process is, to saturate the sap wood with a poison, which, combining with the alburnum, will prevent its being attacked either by insects, or by those fungi which identify themselves with decay. According to Mr. Kyan, who has taken out a patent for preventing the dry-rot in timber, cloth, and a variety of other articles, by steeping them in a saturated solution of corrosive sublimate, oak, fir, and other woods, absorb about the same quantity of the solution ; viz., five ounces for 216 cubical inches, the cost of which is a mere trifle. A fir deal will take in a sufficient quantity to saturate it in forty-eight hours ; but an oak beam will require a month. Canvass, leather, &c., may be completely saturated in an hour or two. It is thought that the outside wood, at present cut oflT as useless, the timber of young trees, and the soft woods, such as poplar, American pine, &c., may by this means be rendered as durable as the harder woods, and as heart wood. (See Quart. Rev., vol. xlix. p. 12.5.) 2189. To lessen the Destructibility of Buildings hy Fire is an important part of the prac- tice of construction ; and one which ought never to be lost sight of by the architectural critic. No building can be completely fire-proof, into which timber enters as a com- ])onent part ; but this timber may in some degree be made to resist fire, by saturation with sulphate of iron : and fire can always be prevented from spreading in a building, by having all the partition walls solid, the interior of them being filled up with brick, stone, or mud ; and by having all the floors of stone, brick, or some earthy composition. Where the floors are of timber, coatings of mortar may be introduced under the boards of the flooring between the joists, in the manner invented by Lord Stanhope, and described in the Annua. Register, vol. xxii. Linings of sheet iron may also be applied between floors and ceilings, and in the middle of partitions ; the panels of doors may be formed of sheet iron, or of corrugated iron, for the same purpose. In all dwelling-houses, where it is an object to guard against danger to life from fire, there ought to be stone staircases, and a balcony to at least one of the windows of each story above the ground floor, to aflbrd means of escape. All houses of several stories ought to have the staircase continued to the roof, not only to admit of easy escape in that direction in case of fire, but to afford ready access to the chimneys when on fire, or when they may require sweeping ; and also for general repairs. As Mr. Kyan's composition by neutralising the albumen of woods, destroys the fermenUitive principle, and thus prevents decay, by putrefaction or rot ; .so, at no distant period, the discovery may be made of some solution of silex, or of some other earth or metal for saturating timber, &c., and thus rendering buildings of com- mon construction indestructible by fire. Such a discovery, added to that of the means of preventing the dry rot, would prove of incalculable benefit to mankind, by diminishing the expense and increaing the durability of the dwellings of the humblest classes, in every part of the world. The architectural critic should be alive to all improvements of such general application, whether realised or anticipated. 2190- To guard against the effects of lightning. The use of lightning conductors is well known. They are commonly made of iron rods, pointed at the upper end, higher than the highest part of the building to which they are attached, and having the lower and inserted in the earth ; the rod following the outline of the building from the highest part to the ground, and being prevented from touching it by glass studs. A more im- proved form, however, has been introduced by a distinguislied philosopher, John Murray, Esq., who has paid the greatest attention to this subject, both theoretically and practically. The following is a description by this gentleman, of a conductor, constructed and at- tached to St. Paul's church, Iluddersfield, in 1831, under his directions. " This con-
