VOLUME TABLES. OT, 
tree by the number of trees. Or, ii the diameters are measured, 
the contents of an average tree of each diameter is multiplied by 
the number of trees having that diameter. This ealculation is 
made for every diameter measured and the results are added 
together. The total result is the amount of standing timber on 
the tract or acre. 
Sometimes cruisers estimate the contents of each tree as it is 
counted in order to avoid computations. For example, the trees 
are noted which contain 100 board feet, those containing 200 board 
feet, 300, 400, 500 board feet, ete. This method is not used except 
where the timber is large. 
Timber cruisers usually know from experience what an average 
tree, or an average tree of any given diameter, will yield in the 
region in which they are working. This knowledge is obtained . 
by measuring a large number of felled trees. If a cruiser under- 
takes to work in a country unfamiliar to him, his first task is to 
determine the contents of the average merchantable tree or of 
average trees of different diameters. 
For some kinds of work, especially where great accuracy is 
necessary, it is desirable to know the contents of trees of different 
heights as well as of different diameters. In this case the cruiser 
measures not only the diameters of the trees which he counts, but 
also determines theiraverage heights. The heights are measured 
by means of special instruments described on page 135. The details 
of this method of estimating are fully explained on page 126. 
Volume Tables for Trees of Different Diameters. 
Volume tables which show the average contents of trees of dii- 
ferent diameters are constructed in the following way: 
A large number of felled trees are measured and the contents of 
each determined. The contents of all the trees of each diameter 
are then averaged together. Thus an average is obtained of the 
contents of all 10-inch trees, of all 11-inch trees, etc. These aver- 
ages are grouped together in the form of a table. The value of the 
table is proportionate to the number of trees measured. 
The tables which follow have been made up in the manner de- 
scribed above. They have been constructed in each case from 
measurements taken in comparatively restricted regions, and no 
claim is made for their accuracy when used elsewhere. 
