38 
BULLETIN 139, U. S. DEPARTMENT OF AGRICULTURE. 
Column 2 shows that for a tree 10 inches in diameter, breast-high, 
every cubic foot of volume in the tree is equal to 4.1 board feet, as 
determined by the Scribner rule, decimal C. 
This table emphasizes the progressive increase in proportional board- 
foot contents of Norway pine, with increasing size, and the impossi- 
bility of converting cubic contents into board feet by a single multiple 
or ratio; these ratios apply only to the contents expressed by the 
Scribner rule. 
The volume table is made by totaling for each tree the contents 
of logs of different diameters. No two log rules give the same con- 
tents in board feet for the same sized log, nor do they maintain the 
same proportional difference for logs of different sizes. Only by 
knowing the actual diameters of the logs in each tree can its volume 
by a new log rule be ascertained. Standard measurements of trees 
should for this reason be taken at definite intervals on every tree and 
averaged for trees of the same diameter and height. A table pre- 
pared in this manner, gives the average upper diameters of trees of 
all sizes and serves as a standard from which the volume may be 
found in any log rule or for any other unit of volume. 
In Table 25, the results of 4,559 trees are averaged at points every 
8 feet above an average stump height of 2 feet. An average length 
of 0.3 foot has been allowed on each 16-foot length for trimming. 
Table 25. — Diameter inside bark of Norway pine logs at intervals of 8.15 feet, on the 
basis of diameter, classed by trees of different heights. 
Diameter 
breast- 
high 
(inches). 
Merchantable length (feet) including stump height. 
10.15 i 
18.3 
26.45 
34.6 
42.75 
50.9 
59.05 
67.2 
75.35 
83.5 
91.65 
99.8 
107.95 
(Diameter inside bark inches). 
30-foot trees. 
2 
1.3 
2.3 
3.1 
4.0 
4.9 
5.9 
6.6 
7. 5 
8.3 
1.1 
1.9 
2.5 
3.3 
3.9 
4.5 
5.1 
5.6 
6.1 
3 

4 
6 


7 
8 

9 


10 

1 
40-foot trees. 
2 
1.6 
2.5 
3.3 
4.2 
4.9 
5.8 
6.7 
7.5 
8.4 
9.3 
10.1 
11.0 
11.9 
1.4 
2.2 
2.9 
3.7 
4.3 
5.1 
5.8 
6.5 
7.1 
7.7 
8.3 
9.1 
9.7 
1.0 
1.6 
2.2 
2.8 
3.3 
3.9 
4.4 
4.8 
5.3 
5.7 
6.1 
6.5 
6.9 
3 
4 
5 
. .. .. 
6 

7 
8 
9 
10 

11 

12 

13 
14 
i The stump height is 2 feet. 
