CHAPTER X. 
FOREST MENSURATION. 
MEASUREMENT OF SINGLE TREES. 
Trees which are to be Cut May be Considered in Two 
Classes, in the first of which fall all those which contain tim- 
ber material, and in the second those which are too small to be 
of value for timber. The material of the first class is in the 
main part available for timber, and in part for firewood, while 
the stump, smaller limbs and leaves are waste; the material of 
the second class may be used in part for firewood, fence posts, 
etc. For timber purposes the cubic contents of the wood only 
is considered, while for firewood the bark is included in the cal- 
culation, so that we may measure part of the tree without bark 
and part with bark on. For timber usually only the main por- 
tion of the trunk is considered, especially in coniferous woods, 
but for firewood all limbs that will make a stick of cordwood 
must be included. In this discussion we will consider only the 
trunks of trees, as the volume of the limbs must be determined 
separately, but in the same way. 
The Volume of a Standing Tree can be gotten at only 
roughly, as there is no geometric figure which exactly represents 
the shape of the trunk, the latter varying much under different 
conditions of growth. The volume of a paraboloid, the 
geometric figure which approaches nearest to the form of a 
tree, is equal to the product of the basal cross-sectional area by 
one-half the height. The basal area of a tree is taken at breast 
height, to avoid the excessive swelling near the ground. Breast 
height is usually considered as four feet three inches above the 
ground, at which point the diameter is measured by a pair of 
calipers in inches, and the area in square feet of the correspond- 
ing circle is found in a prepared table of such areas. The height 
of the tree may be determined by triangulation, in which various 
instruments are used, as the transit, the altimeter, or a mirror 
