test, correction for locality is unnecessary. If, on the other 
hand, the local trees consistently differ from the tabular values, 
the table should be corrected for local use. 
To prepare a local volume table ® from the 20 to 25 trees above 
referred to, percentage relations, averaged for each inch-class 
represented by the local trees, should be established as between 
the local and tabular values and curved over diameter. If 
these relations are not uniform for trees of all height classes, 
separate curves may be necessary for tall, medium, and short 
trees. The final smoothed percentages should then be applied 
to the tabular values, making a new table for local use. 
CoE ON OF VOLUME TABLES FOR DIFFERENT LIMITS OF UTI- 
The limits of utilization upon which the tables are based do 
not coincide with actual utilization in all parts of the region. 
Where they differ, correction of the tabular values is necessary. 
For volumes in cubic feet or cords it is sufficient to measure 
the length of a few felled trees (the 20 or 25 used in the test just 
described will do very well) to both the limit used in the table 
and that set up by the conditions of actual utilization. By sub- 
traction the lengths of the section to be deducted or added are 
then obtained, and their volumes calculated in the proper unit. 
These will vary somewhat with the breast-high diameter of the 
trees, and possibly with their height as well; smoothed values 
should be obtained by curving the raw data. Corresponding 
deductions or additions are then made in the regional tables. 
For volumes in board feet it is necessary to go through the more 
laborious process of scaling the trees to both limits and obtaining 
by subtraction the board-foot differences. 
Correcting board-foot tables in which merchantable heights 
are expressed in number of logs in this way may easily lead to 
errors in their use. Suppose, for example, that the top limit for 
use in calculating board feet by the International rule is 8 inches 
instead of 5. Then trees that contain four logs to the 5-inch 
top, and appear in the regional table here given as 4-log trees, 
drop to perhaps 8-log trees to an 8-inch top. If such trees are 
tallied in the field as 3-log trees, their volumes as taken from 
the revised tables will then be much too low, unless the head- 
ings for height have also been revised. This can of course be 
done, but perhaps the easier way, if relatively small use is to be 
made of the revised tables, is to continue to tally these trees in 
the field as 4-log trees—of course, estimating height to a 5-inch 
top. The unused volume, between the 8-inch and 5-inch tops, 
can be cared for by a percentage deduction, as for cull. Itisa 
6 A volume table based on diameter alone, disregarding heights, is often called a 
local volume table; this is not the meaning in the present instance. 
4 
