Remark.—It is highly probable (though the experiment has not been tried) that this composition would be improved by adding a small portion of the liquid leather, which is now commonly sold in London, being the refuse of the purification of fish oil by tar.
Where the work will bear the expense, and is not exposed to a heat of more than 130 degrees of Fahrenheit, the best composition is the following: Equal parts of turpentine (the fluid resin, not the essential oil), bees'-wax, black resin and maltha, or coal tar, boiled together till they cease to rise—that is, till the white cream or scum proceeding from the separation of the essential oil disappears. Apply it warm with a turpentine brush—two or three coats, to cover the cracks or pores left by the brush. This lute was first proposed by Chaptal, without the addition of the coal tar, which is a great improvement. A piece of wood covered with three coats of it, and immersed for two years in water, was found to be quite dry on cutting off the lute.
Take care not to allow water to fall into the pan, as it would make the hot materials explode. If the composition catch fire, put on the cover directly, and remove the pan for an instant from the fire.
1138. Cause and Prevention of the Dry Rot.—The cause of the dry rot in wood is moisture; and to prevent well-dried timber from decaying above or under ground, is done by charring it well.
1139. Cure for the Dry Rot in Timber, so as to make it indestructible by Water.—Melt twelve ounces of resin in an iron pot; add three gallons of train oil, and three or four rolls of brimstone; and when the brimstone and resin are melted and become thin, add as much Spanish brown, or red and yellow ochre, or any other color required, first ground fine with the same oil, as will give the whole a shade of the depth preferred; then lay it on with a brush as hot and thin as possible; some time after the first coat is dried, give it a second. This preparation will preserve planks for ages, and keep the weather from driving through brick work.
1140. Method of trying the Goodness of Timber for Ship-building, used in the Arsenal at Vienna.—One person applies his ear to the centre of one end of the trunk, while another, with a key, hits the other end with a gentle stroke. If the tree be sound and good, the stroke will be distinctly heard at the other end, though the tree should be a hundred feet or more in length.