YIELD OF ASSOCIATED SPECIES 89 
lumbermen, but in the case of the other species in 
mixture twelve inches was made the minimum diam- 
eter. Mr. Jacobs, from whom the table for Birch was 
obtained, estimated that although Hard Maple would 
contain more feet of wood than Birch, the amount of 
merchantable timber per tree would be from five to ten 
per cent. less, on account of the greater proportion of 
cull. The estimate for Hard Maple was accordingly 
made by deducting eight per cent. from the contents of 
the trees as given in the table for Birch. The yield of 
White Pine was determined by the use of the volume 
table for board feet contained in the study of that tree 
by Pinchot and Graves. The table given below, which 
was employed in determining the amount of Hemlock 
in the Park, is used by the lumber cruisers in northern 
Michigan. 
TABLE 29 
STANDING HEMLOCK 
Diameter No. of trees 
_in per 1000 
inches. board feet. 
18 4 
20 3 
22 24 
~_— F 
26 1% 
28 1y% 
