IMPROVING THE QUALITY OF WOOD. 507 



wood for years in airy places, where the wood was kept first 

 in the open and exposed to moisture from the air, then in 

 shady, dry chambers and finally in heated ones. At present 

 there is not usually space enough for this, and the process 

 is too costly, so that wood is sold either unseasoned or is 

 seasoned artificially. Artificial seasoning is employed 

 extensively in America. In Zappert's method of seasoning 

 wood, planks, boards, laths, etc., are exposed to air heated to 

 30 C. (59 F.), while an exhauster removes the damn air; 

 in this way dry softwoods become dry in 6 to 8 days, hard- 

 woods in 12 to 15 days, without exhibiting cracks or any 

 deterioration in colour, elasticity, etc. If the air is also rare- 

 lied, according to SchafYenius, the desiccation is more rapid. 

 Wood may also be placed to dry in dry, line sand, charcoal- 

 dust or powdered pe;it. Wood intended for water-pipes is 

 plunged in water in order to prevent cracking. After the 

 wood is dried thoroughly, a coating of oil, paint, varnish, lac or 

 polish, protects it from moisture, as has been described already. 

 Warping may be prevented also, by constructing articles of 

 small pieces of wood, which are fastened together (billiard 

 cues, parquetry, drawing-boards), or spaces are left to allow 

 for expansion (door-panels, wooden ceilings, etc.), or species 

 of wood are selected that are known to be only slightly absorptive 

 of water. 



7. Incrr<(8<> in 



The pliability of wood is increased by means of moisture 

 and heat. Bent furniture is made of steamed wood, so are 

 felloes of wheels and curved planks in carriage-making and 

 ship-building. 



8. Increase in Durability. 



There are numerous ways of increasing the durability of 

 wood ; some of them can be employed before a tree is felled. 

 That girdling the lower part of a stem, or felling it with its 

 crown of foliage, are not effectual has been stated already 

 (p. 506). E. Mer recommends that a ring of bark should be 

 removed immediately under the crown, not in order to dry 

 the stem, but that the latter may be deprived of its sugar and 



