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 



