74 ELEMENTARY FORESTRY. 



Good Coatings for Wood consist of oily or resinous substances 

 that are easily applied in a smooth coat and dry readily, yet 

 do not have any tendency to crack or peel off. They should 

 be applied to the whole exposed surface. 



Coal Tar is one of the best materials for covering wood to 

 increase its durability. It is best applied hot, especially if 

 mixed with oil of turpentine as it then penetrates more deeply. 

 A mixture of three parts coal tar and -one part unsalted 

 grease to prevent the tar from drying too quickly so it may 

 penetrate the wood better is recommended. One barrel of 

 coal tar will cover from two to three hundred posts if it is 

 properly applied. 



Oil Paints are next in value. Boiled linseed oil is used 

 with lead, pulverized charcoal or other similar material to 

 give it substance. Soaking the dry wood in crude petroleum 

 is also recommended. 



Lime White Wash is a good preventive of decay in wood 

 and although not as good for this purpose as coal tar it i& 

 very desirable. As with all other preservatives that are ap- 

 plied to the surface, the wood should be very dry before it i& 

 applied and the wash should be applied evenly over all the 

 exposed parts. It is on account of the lime that washes out 

 of the mortar that the shingles on a roof just below the chim- 

 ney last longer than on other parts of the roof. But if white 

 wash is to be applied to shingles it should be applied before 

 they are laid by dipping. 



Charring those parts of posts or timbers which come in con- 

 tact with the ground is a good preventive provided a thick 

 layer of charcoal is formed and the work so carefully done as 

 not to cause the timber to crack since deep cracking exposes 

 the interior to decay. If not carefully done the timber may 

 be seriously weakened. 



Antiseptics. The impregnating of timber with sulphate of 

 copper (blue stone), sulphate of iron (green copperas), 

 chloride of zinc, creosote, salts of mercury or other similar 

 material has the effect when properly done of greatly in- 

 creasing its durability. Such antiseptic substances have the 

 power of destroying the rot-producing fungi. The materials 

 are generally applied to fresh logs. If dry timber is to be 

 treated, it is- first boiled or steamed to open the cells. A 



