TIMBER ESTIMATING. . 61 
Volume Tables.@ 
Volume tables show the average contents of standing trees of 
different sizes; they are used extensively in estimating timber. 
They may be made for any desired unit—the cubic foot, board 
foot, standard, cord—or they may show the contents of trees in 
ties, poles, shingles, or other product. They are used to estimate 
the yield of wood and timber standing on specified tracts. Vol- 
ume tables are intended only for estimating a large number of 
trees. Compiled from the average of a number of measurements, 
they are necessarily inaccurate as applied to a single tree. The 
volumes of individual trees of the same species and same dimen- 
sions may vary 20 per cent or more. On the other hand, the 
average volume of a large number of trees of the same species, 
having the same height and diameter and growing under the same 
conditions, is very uniform, and tables showing the average vol- 
umes of a large number of felled trees give satisfactory results in 
estimating the contents of a large number of standing trees. 
VOLUME TABLES BY DIAMETER ONLY. 
The simplest volume tables show the average contents of trees 
of different diameters. The total contents of trees of any given 
diameter are computed by multiplying the number of trees by 
the average volume given in the volume table for that diameter. 
The tables are based on the measurement and computation of - 
volume of a large number of felled trees. The contents.of all 
trees of each diameter are then averaged. Thus an average is 
obtained of the contents of all 10-inch trees, of all 11-inch trees, 
and so on up. These averages are grouped together in the form 
of a table; the value of such a table is proportionate to the number 
of trees measured to form its basis. 
Volume tables by diameters alone are very limited in their 
application, because trees upon different tracts and on different 
portions of the same tract vary greatly in height and consequently 
in volume for the same diameters. Such tables can not be 
depended on unless it is known that the average height of the 
aAll volume tables are given in the Appendix- 
