No. 1, July, 1920) FORESTRY 73 



summarized. Witter occurs as liquid in the cells and vessels and aa imbibed or hygroscopic 

 moisture in the walls. The latter, at the "fiber saturation point," is generally aboul 25-30 

 per cent calculated upon the dry weigh! of the wood. "'< lasehardening," which is the drying 

 and setting of I he outer cell walls before these within the wood have dried oul , is a frequent 

 phenomenon. Shrinkage is the resull of the drying ou1 of imbibed water and is about twice aa 

 much circumferentially as radially and one fiftieth as much longitudinally. Due to the 



special properties of h I, drying is complicated by the four factors, moisture, shrinkage, 



stresses and hardening and cannot be calculated simply in terms of the Dumber of thermal 

 units necessary to eliminate all moisture. The slow rate of transfusion of moisture, the 

 irregular rates of shrinkage, the frequent BOftening of wood substance or the loss of cohesion 

 among the fibers, at elevated temperatures, the warped condition of wood fibers, the influ- 

 ence of elevated temperature combined with various degrees of moisture, the brittleness of 

 wood caused by excessive drying, and its hygroscopic character, the color changes and the 

 collapse of cells — all these help to cause internal stresses "which are the main cause of warp- 

 ing, checking and honey-combing." These stresses may be temporary or permanent depend- 

 ing upon the "relative degree of hardening of the outer and inner fibers and the relative 

 amounts of residual shrinkage when they become uniformly dry." The internal fibers may 

 be pulled apart by the internal stresses, thus giving rise to "honey-combing." Caseharden- 

 ing generally increases with rapid drying out and is less with a slower rate, since the trans- 

 fusion of moisture keeps more nearly abreast of evaporation. The stresses for "several 

 assumed progressve conditions of casehardening and reabsorption" are analyzed in terms of 

 the relative compressions and stretchings of the outer and the inner layers of fibers, showing 

 that the "maximum total stresses are very apt to occur in the first stages of drying" and 

 that "the tension inside the block is at no time as intense as on the surface." — Ernest Shaw 

 Reynolds. 



477. Walker, H. C. Forest policy in Burma. Indian Forester 45: 173-187. 1919. 



478. Waterson, D. Vanishing forests. Sci. Amer. 121:383. 1919. — A brief considera- 

 tion of forest conditions in New Zealand. — Chas. H. Otis. 



479. Waterson, D. White pine and butter. Sci. Amer. 121:372. 1919.— Describing a 

 tub made of two thicknesses of veneer rs inch thick and used in New Zealand and Australia 

 as a butter container. — Chas. H. Otis. 



480. W Atkins, J. R. Pitch pockets and their relation to the inspection of airplane parts. 

 Jour. Franklin Inst. 188:245-253. Fig. 1-3. 1919. — The theories concerning the origin of 

 resin pockets and their effects upon airplane timber are discussed. The injury to such timber 

 varies with the size and position of the pockets, the smaller ones apparently not materially 

 weakening the airplane parts. — Ernest Shaw Reynolds. 



481. Weber, H. Zur kiinftigen Besteurung des Waldbesitzes. [Future taxation of forest 

 land.] Allg. Forst-u. Jagdzeitg. 95: 25-32. 1919. — The war, and its results have made it neces- 

 sary to levy extraordinary taxes on all forms of property and incomes. Owing to the pecu- 

 liar nature of the forest as an investment it is difficult to make proper assessment of value 

 and corresponding tax. It is extremely important however that care be taken to enact the 

 right kind of laws governing taxation of forest property. Otherwise, great if not irreparable 

 damage might be done as a result of overcutting in order to meet the tax demands. The 

 writer outlines, in some detail, a system of taxation which he thinks will help to solve this 

 important problem. — Hefmann Krauch. 



482. Weir, James R., and Ernest E. Hubert. A study of the rots of western white pine. 

 U. S. Dept. Agric. Bull. 799. 24 V- 1919— See Bot. Absts. 4, Entry 1379. 



483. Wibeck, Edvard. Om tall- och granfro fra Norrland. [Concerning pine and spruce 

 seed from Norrland (Sweden).] Skogen 6: 97-107. Fig. 1-3. 1919.— The importance of the 

 source of seed for reforestation as disclosed by previous investigations and experiences is 



