506 AUXILIARY FOREST INDUSTRIES. 



wood instead of heavy oakwood, or veneered softwood instead 

 of massive hardwood. 



6. Improvements in Hygroscopicity. 



In order to counteract as far as possible the evils of the 

 varying humidity of w T ood, such as warping, cracking, swelling 

 and contracting, the following remedial measures are available. 



To prevent air-cracks and heartshake in logs, it has been 

 recommended that trees before they are felled may be barked 

 to a height of one meter and not felled until they are dead. 

 The leaves then pump out much water from the stern. 

 E. Hartig has, however, shown that the leaves die before the 

 stem has lost a third of its contained water. Even the girdling 

 of a tree down to the heartwood, which kills conifers in a few 

 weeks, does not kill broadleaved trees till 1 to 3 years, so that 

 in this experiment, as well as in that of leaving the crown 

 with its foliage on a felled tree, the leaves dry up long before 

 the stem has become appreciably dry. These practices, which 

 appear so plausible and easy, have appeared in literature for 

 more than a century ; they were recommended even by Pliny. 



Better remedies may be tried after a tree has been felled, 

 such as partial barking the tree along the stem in pieces of a 

 hand's width, or the removal of the bark in a spiral up the 

 stem so as to delay the drying and the formation of cracks. 



In order to prevent star-shake at the base of a log, paper 

 may be glued on. Paper is glued on to all the surfaces of 

 valuable exotic balks ; pieces of bark may be nailed on ; on 

 pieces of thin planks of wood, grease may be laid, or carbo- 

 lineum, wax, clay, petroleum, linseed oil, tar, rabelka (sebasate 

 of alumina), soluble-glass; or S-shaped clamps driven into the 

 wood. It is generally believed, that by washing out the soluble 

 salts, plasma and sap of wood, not only its durability is 

 increased, but also cracking is prevented and warping reduced. 

 Hence floating, rafting, boiling and steaming are recommended. 



Impregnating wood with various substances is a good pre- 

 servative against warping, although the chief object is to 

 render it more durable. Thorough desiccation of the wood 

 is highly effective. Formerly this was secured by storing the 



