As a means of preventing this evil, the timber is sometimes scorched over a flame, turtling it about till every side acquires a sort of crusty surface ; in doing this, it necessarily follows, that the external moisture is dissipated. After this process, a mixture of pitch and tar, sprinkled with sand and powdered shells, may be advantageously applied to the parts intended to be under water, while those more in sight, after being well scorched, and while the wood is hot, should be rubbed over with linseed-oil mixed with a little tar. This will strike deeply into the grain of the wood, and will soon harden so as to receive as many coats of paint as may appear necessary.
It has been found, that fir-timber, thus prepared is nearly equal to oak for durability.
The following valuable observations on the seasoning, of timber are extracted from an able article on "Timber—Its Treatment and Uses," by Mr. James \Vylson, published in the Second Volume of the " Builder :"— " There arc natural and artificial means of seasoning, both of which have their recommendations ; but the former has certainly the right of preference, as it gives greater toughness, elasticity, and durability, and therefore should always be em ployed in preparing timber for carpentry.
" When there is time for drying it gradually, all that is necessary to be done, on removing it from the damp ground of the forest, is to place it in a dry yard, sheltered from the sun and wind, and where there is no vegetation ; and set it on bearers of iron or brick in such a manner as to admit a cir culation of air all round and under it. In this situation it should continue two years, if intended for carpentry, and double that time if for joinery, the loss of weight, which should take place to render it fit for the purposes of the for mer, being about one-fifth, and for the latter about one-third. If it is to be used round, it is good to bore out the core, as by so doing, the drying is advanced, and splitting prevented, with almost no sacrifice of strength. If it is to be squared into logs, it should be done soon after some slow drying, and whole-squared if large enough; as that removes much of the sap-wood, and liteilitates the drying, and prevents the splitting, which is apt to take place when it is in the round form, in consequence of the sap-wood drying before the heart, from being less dense ; also, if it may be quartered, it is well to treat it so after some time, as the seasoning is by that means rendered more equal. It is well also to turn it now and then, as the evaporation is greatest from the upper side.
To prevent timber warping, it should be well sea,oned before it is emit into scantlings, and the scantlings should be cut some time belbre they are to be used, in order that the seasoning may be as perfect as possible; and if they can be set upright, so much the better, as then they will dry more rapidly, and, as the upper dries sooner than the lower side, they ought therefore to be reversed at intervals.
" When there is not time for actual drying, the best method that can be adopted, especially for sappy timber, and if strength is not principally required, is immediately, on fell ing, •:o immerse it in running water, and, after allowing it to rent iin there about a fortnight, to set it in the wind to dry. This renders timber less apt to crack and warp in drying, and less subject to be worm-eaten, especially the more ten der wools; but it must be altogether under water, as partial immersion is very destructive.
"Of steeping generally, whether in cold or warm weather, it must he observed, that it dissolves the substance of the wood, and necessarily renders it lighter ; therefore the less that is necessary of it the better; indeed, it is known, that, notwithstanding wood that is completely submersed remains good for a very great period after the water has dissolved a certain soluble part, it is, when taken out and dried, brittle, and in every respect unfit for use.
"For the purposes of joinery, steaming and boiling are very good methods, as the loss of elasticity and strength which they produce, and which is so essential in carpentry, is compensated by the tendency to shrinkage being reduced ; the durability also is rather improved than otherwise, at least from steaming. It has been ascertained, that of woods sea soned by these methods, those dry soonest which have been steamed ; but the drying in either ease should be somewhat gradual, and four hours are sufficient for the or steam ing process." Langton's method of seasoning by extraction of the sap, is another that is considered well worthy of notice ; it consists in letting the timber into vertical iron cylinders at top; and the water being heated, and steam used to produce a partial vacuum, the sap relieved from the atmospherical pressure oozes from the wood, and, being converted into vapour, passes off through a pipe provided for the purpose. The time re quired is about ten weeks, and the cost is about ten shillings per load ; but the sap is wholly extracted, and the timber fit and ready for any purpose; the diminution of weight is, with a little more shrinking, similar to that in seasoning by the common natural process.