78 FOREST UTILIZATION 



II. Piling. 



Strong, liigh, horizontal ground sills are of the utmost 



importance. The front sill should be higher than the 



middle and back sills, except in shed drying. 

 In some yards the front of the piles is given an overhang- 

 ing "batter," to protect it from rain, an arrangement 



feasible only in low piles. The usual pitch of the pile 



is I foot in 10 feet or more. 

 The tiers of boards are kept apart by three or four well 



seasoned 'cross pieces called sticks — sawn i inch square 



and placed directly one over the other. 

 The usual width of the. piles is from 6 feet to lo feet. 

 The distance between the piles is at least one foot and 



should be three feet. 

 In order to prevent end cracks, the sticking should be 



placed exactly at the ends, slightly projecting over the 



ends. 

 Each pile must contain equal lengths, as "overlaps" are 



sure to get spoiled. 

 Valuable wide boards are often painted at the ends. 

 Oak, ash, hickory and elm require at least four months 



for air drying; lynn, poplar and pine about two and 



a half months. 

 Slow drying involves a loss of interest, large yard room, 



large insurance and slow filling of orders. Still in the 



case of high grade hardwoods, the use of the dry kiln 



is disastrous to the lumber. 

 Thin lumber does not check as badly as thick lumber. 



Squares check worst of all. 

 A fermentation and incidentally a discoloration takes place 



where two fresh, sawn surfaces touch one another. 

 Each pile should have a roof 12 inches high in front and 



6 inches high in back, projecting in all four directions 



over the pile. 

 Proper curing of lumber is as important as proper sawing 



of lumber. 

 III. Dry kiln. 



A dry kiln consists of 



shed with gates closing tightly; 

 lumber conduit; 

 heating apparatus. 



The heat is supplied — slowly — 

 either by a hot air fan; 

 or by a system of steam pipes; 

 or by steam admitted into drying room. 

 The air in the dry kiln must be kept in constant move- 

 ment, so as to prevent unequal drying of the lumber 



in the piles. 



