THE AIR SEASONING OF WESTERN SOFTWOOD LUMBER 39 
practice is that of improper bearing of the crossers. Bowed stock 
and other forms of depreciation result from crossers not bearing 
directly on those beneath. The vertical alignment of each tier of 
crossers should approximate the pitch of the pile. The front crosser, 
and the rear crosser in box piles, should be consistently placed so 
that they project beyond the ends of the stock. When stock 6 inches 
and wider is self-crossed, at least 2 inches of the crosser width should 
overhang to avoid end checking, and where 4-inch special crossers 
are employed this overhang should be at least 1 inch. The difficulties 
of this method are greatly exaggerated and the merits fully justify 
insistence upon its use. Observation alone should convince any one 
of the effectiveness of this practice, even if actual pile comparisons 
did not fully substantiate it. In pine stock piled with the crossers 
flush with the ends, eight times as much check developed as in stock 
protected by overhung crossers. A similar test with inch Douglas 
fir stock showed end checking of 20 and 3 per cent, respectively, when 
the two methods were employed. 
Some yards using stock crossers, particularly stock 8 inches and 
wider, stagger the center and rear crossers about half their width. 
(Pl. 5, D.) By this method, the portion of the board ordinarily 
covered on both sides by the crosser is exposed to the air on one side. 
This results is a shghtly lower final moisture content in these sec- 
tions, and it is said that less checking of stock and crossers occurs. 
On the other hand, such practice does not lessen crosser stain and, 
especially with 4/4 stock, invites depreciation in the form of bowed, 
warped, and twisted lumber. 
SPACING BETWEEN BOARDS 
A. fundamental principle of air-seasoning and one which appar- | 
ently fails to receive proper recognition in yard practice, is that 
there must be vertical air circulation in the lumber pile. This in- 
ternal downward movement resulting from the natural tendency of 
the moist air, cooled by evaporation, to drop toward the bottom 
of the pile, must be positive throughout the pile in order to make 
the drying process most effective. Best results are therefore obtained 
when lumber is piled in even widths, permitting unbroken vertical 
flues extending from the top to the bottom of the pile between each 
two tiers of boards. In random-width stock such construction is 
ordinarily impracticable, and, accordingly, a relatively wider spacing 
between boards in the course is necessary to offset as far as possible 
this disadvantage. 
The interval between boards can to some extent control the rate of 
drying. Extremely rapid drying and consequent depreciation from 
checking can be moderated by a reduction of this spacing. On the 
other hand, the drying rate can be increased, the lag in drying 
between lower and upper sections of the pile can be decreased, and 
blue-stain losses reduced by a greater spacing. One obstacle, how- 
ever, to control of drying rate by spacing is that wide spacing reacts 
proportionately in all parts of the pile and thus may improve the 
drying process in one portion at the expense of creating a more 
serious condition in another. Hence, spacing must be supplemented 
by other methods in order to obtain the most uniform drying. 
