THE AIR SEASONING OF WESTERN SOFTWOOD LUMBER 39 
10-inch vent at the center failed to show any increase in either the 
rate or uniformity of drying over piles with a 3-inch spacing and 
no vent. 
An adaptation of the chimney method may, however, be used to 
advantage with even-width stock in yards where the evils resulting 
from slow drying in the lower part of the piles are a primary prob- 
lem. What are in effect short chimneys are formed by simply elimi- 
nating every other board in the course for the first 4 or 5 feet of the 
pile. The merits of such a method are the increase of vertical circula- 
tion in that part of the pile where it is most needed at a sacrifice of 
space in that section alone. The obvious disadvantage, that of insuf- 
ae bearing surface for the crossers, is not serious except with wide 
stock. 
The use of chimneys in piles of random-width stock is of course 
entirely justified. It is, indeed, the only practicable means of creat- 
ing a direct vertical circulation in piles of this type. The single 
straight center chimney is undoubtedly of value, but the rate and 
degree of drying attained are far from being as favorable as those 
obtained in properly constructed even-width piles; and stain losses 
are usually very heavy. Two chimneys are likely to give better 
average conditions, although the center section of stock between them 
is probably subject to more severe stain depreciation. The center 
A-shaped or “ flared ” chimney, 8 inches in width at the top and 22 
inches wide at the bottom, is superior to either single or double 
straight chimneys. It not only makes a maximum provision for 
vertical circulation where that is most needed but in so doing elimi- 
nates stock from that part of the pile which is subjected to the very 
worst drying conditions. This method is also economical of space 
in the upper sections. 
If three to eight chimneys are employed, evenly distributed from 
one side of the pile to the other, an approach is made to the desirable 
conditions obtained in piling even-width stock. Positive vertical 
circulation throughout the pile is more nearly attained. Within each 
of the four to nine vertical sections of stock thus set apart the 
boards in a course should be placed as nearly tight as the widths 
will permit when the outer boards of each section are kept flush 
with the sides of the chimneys. This general system has advantages 
over the other chimney methods discussed. The pile capacity is 
greater because of the relatively narrow chimneys, usually 6 or 7 
inches, and the close piling between them. The rate of drying is 
more rapid, and less stain develops as a consequence. Degrade from 
checking is also smaller because, although the chimneys allow good 
vertical circulation, the principal effect of this is to build up the 
horizontal air currents that permit uniform drying across the face 
of the stock. On the contrary, with fixed spacing between the boards 
in a course, short flues occur blocked above and below by wider 
boards. Air currents following these flues strike the projecting 
board and effect an unequal drying that often causes checking. 
Controlled yard tests of these several methods show clearly that 
the use of chimneys in random-width stock has a very definite effect 
upon drying and indicate the relative merits of the different methods. 
Comparisons were made of the pile without chimneys, the pile with 
two 12-inch chimneys 414 feet apart, and the pile with a center flared 
