TIMBER.

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men, and produced an insoluble precipitate. This precipitate fills up all thecellular interstices of the wood, and becomes as hard as the fibres.

620. Ventilation of Timber in Dwellings. —Even after timber lias been subjectedto this process, it is requisite to give the air free access to it by means of ven-tilation, and for that purpose, where timber is covered up, which it is not likelyto be in a steading, small openings, covered and protected by cast-iron gratingsin frames, should be made through the outside walls.

621. Other plans for preserving timber have been introduced, of which thefour most important are known as Burnett ’s, Bothell's, Bayne’s, and Bou-cherie’s : of these we offer a short description.

622. Burnett’s Process. —The process patented in 1842 by Sir William Bur­ nett consists in impregnating the timber with a solution of the chloride of zinc.From recorded experiments, the process seems to be efficient. The solution isprepared in the proportion of 1 pound of chloride of zinc to 10 gallons of water.

623. BelheU’s Process. —In Bethell’s process, oil of tar, and other bituminousmatters containing creosote, are used to impregnate the wood. The wood is notonly immersed in the solution, but it is forced into the fibres by pressure. Thewood to be impregnated is placed in close tanks filled with the solution ; thetanks are then closed up, and the air exhausted from their interior ; more solu-tion is then pumped in for a period of six or seven hours. The wood is finallytaken out thoroughly saturated with the solution, and weighing considerablyheavier. The process is said to perfectly coagulate “ the albumen in the sap,thus preventing its putrefaction.” In using the oil of tar it is necessary todeprive it of its ammonia, otherwise the wood becomes brown and soon decays.

624. Timber for farm purposes may be simply Bethellised by painting thesurface over with the hot oil of tar, or by immersing it in a tank of the hot solu-tion. This will not give such beneficial results as when impregnated underpressure, but will nevertheless tend to preserve the timber for a considerabletime from atmospheric influences. The cost of the oil, as sold by the patentee,is stated at 4d. per gallon.

625. Pagne's Process. —In Payne’s process (patented 1841) the wood is im-pregnated by pressure with a solution of earthy or metallic substances ; andthese substances, by chemical decomposition, preserved within the material inan insoluble state. Thus, if a solution of sulphate of iron is forced into thewood, a second solution is forced in of any of the carbonate alkalies, which“ decomposes the salt, and renders the iron insoluble.”*

626. Boucherie’s Process. —This process consists essentially of impregnatingthe wood with a preservative solution. The solution which is found to answer bestis sulphate of copper, or the blue vitriol of commerce, one by weight of whichis dissolved in 100 by weight of water. The peculiarity of the process, how-ever, consists in the method of impregnating the wood with a solution—a methodwhich is simple, and easily and inexpensively carried out. The method hastwo objects in view—one the impregnating of the wood with the salt, and onethe driving out of the natural sap—the salt taking the place of the sap. Thislatter constitutes not the least valuable part of the process ; for in othersystems the sap—the fermentation of which is the chief cause of decay in wood—is allowed to remain, while the Boucherie process expells it thoroughly,cleansing the tubes or pores from all fermenting matter. The importance ofhaving the sap of timber expelled, and its place occupied by the preserving solu-tion, has long been recognised ; and attempts have been made to secure the ad-

* See Transactions of the IIiyhland and Agricultural Society for 1857, p. 12 —art. “The Preser-vation of Timber.”