38 DEPARTMENT BULLETIN 1425, U. S. DEPT, OF AGRICULTURE 
fore, a relatively wider spacing is necessary than for even-width 
stock in order to offset this lack of well-defined channels for vertical 
circulation. The effect of increased width is well shown by actual 
yard comparisons. Random-width 6/4 No. 1 shop-and-better sugar 
pine piled with a 38-inch spacing resulted in a total degrade of 11.8 
per cent; with a 5-inch spacing, in a degrade of 5.3 per cent; and 
with a 7-inch spacing, in a degrade of 4.8 per cent. The reduction in 
stain development accounts for practically the total difference be- 
tween the first and second tests. Although stain was practically 
eliminated by the 7-inch spacing, increased defects resulting from 
very rapid drying largely discounted that advantage. ‘This indicates 
that methods of hastening seasoning must not be carried too far. 
Although in each region the spacing allowed in piling random- 
width stock averages slightly larger than that employed for even 
widths, a still wider interval is very generally needed. At numerous 
plants a real improvement in seasoning conditions can be obtained 
by this means. 
CHIMNEYS OR VENTS 
Very closely related to proper spacing is the procedure of building 
chimneys or vents into the lumber pile as a means of improving 
vertical circulation. Chimneys are unobstructed vertical openings 
quite distinct from the flues obtained by the uniform spacing of even- 
width stock. They are normally wider than flues and are located 
only at the center of the pile or at definite intervals across the width 
Their most effective use is with random-width stock. 
Little uniformity in the practice of using chimneys is evident, and 
this results in large measure from a lack of accurate knowledge of 
the real influence of this feature of pile construction upon actual 
drying conditions within the lumber pile. At some redwood plants 
both even and random width stock are piled with two chimneys 10 
to 16 inches wide, and at others no chimneys are employed. In the 
California pine territory the chimney is little used with even widths, 
but the straight center vent 8 to 20 inches wide is very generally 
utilized with random stock. Inland Empire plants rather commonly 
pile even-width pine with an 8-inch center chimney and employ a 
large assortment of vent combinations in the seasoning of mixed 
widths. A 6 to 12 inch center chimney is most common. Two 8 or 
10 inch chimneys are not unusual, and some plants make use of from 
three to eight narrow vents distributed across the pile. Chimneys 
find little use in the Douglas fir region and where employed are 
generally of the single center type. 
Since the only purpose of chimneys is to aid vertical circulation 
throughout the lumber pile, it is more logical in seasoning even- 
width stock to increase the spacing between the boards in a course 
and thus the width of the vertical flues, than to use a relatively nar- 
rower spacing and place a center chimney in the pile. This con- 
clusion has been confirmed by numerous actual yard comparisons of 
the results obtained from both methods of piling. At several plants 
in the Inland Empire even-width pine stock piled with a 3-inch 
spacing was air-dried in less time and developed slightly less stain 
than did the same stock piled closer and given a 12-inch center 
chimney. In the Douglas fir region, piles with 2-inch spacing and a 

