. Bulletin. Forests and forestry -- United States. 56 TIMBER. conditions, or else in the use of poisonous salts, which prevent the prop- agation of fungi. It is also apparent, therefore, why wood decays faster in Alabama than in Wisconsin, faster in the swamps than on the plains, and why the presence of large quantities of decaying wood about the yard, constantly producing fresh supplies of spores, stimulates decay. Cov- ering with tar or impregnating with creosote, salts of mercury, copper, etc., enables even sap- wood to last under the most try- ing conditions. Contact with the ground assure
. Bulletin. Forests and forestry -- United States. 56 TIMBER. conditions, or else in the use of poisonous salts, which prevent the prop- agation of fungi. It is also apparent, therefore, why wood decays faster in Alabama than in Wisconsin, faster in the swamps than on the plains, and why the presence of large quantities of decaying wood about the yard, constantly producing fresh supplies of spores, stimulates decay. Cov- ering with tar or impregnating with creosote, salts of mercury, copper, etc., enables even sap- wood to last under the most try- ing conditions. Contact with the ground assures most favorable moisture conditions for fungus growth, and the higher tempera- tures near the surface of the ground, together with the ever- present supply of spores, cause rot in a post to start at the sur- face more readily than 30 inches below. The use of means to prevent decay is therefore desirable where timber is placed in positions favor- able to fungus growth, as in rail- way ties; and all joists and timber in contact with damp brick walls, as also all building material whose perfect seasoning is prevented by the absence of proper circulation of air, should be specially pro- tected. In the former cases it is economy to apply preservative processes; in the latter a sanitary necessity. Wood covered with paint, etc., before it is perfectly seasoned, falls a prey to "dry rot 5" the fungus finds abundance of moisture, and the protection intended for the wood protects its enemy, the fungus. Since char- coal resists the solvents of fungi, charring the outer parts of posts makes, if well done, namely, so as not to open checks into the interior of the wood, a very fine protection. Under ordinary circumstances, only the second great factor of decay, i. e., the moisture condition, can be Fig. 36.—Cells of maple wood attacked by fungus threads (Nectria cinnabarina Mayer). Section of three wood fibers showing the threads of the fungus branching in their cav
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