64 THE WOODSMAN’S HANDBOOK. 
Even when used in very irregular stands, where the trees differ 
largely in age and development of crown, such tables are more accu- 
rate than volume tables based on diameter alone. 
Volume tables based on diameter and height have been con- 
structed for several species in this country and used in the practical 
work of estimating. They give good results with trees of regular 
form like the pines and spruces, but with the hardwoods they are 
not entirely satisfactory unless separate tables are made for different 
tree classes. 
Volume tables may be made for poles, and it would be of great 
practical value to have tables showing the average length and top 
diameter of poles yielded by chestnut of different diameters, or 
the length and middle diameter of piles contained in pitch pines 
of different sizes. 
The purpose of studying the volumes of single trees is to facilitate 
the compilation of the contents of stands. Occasionally a single 
tree is sold, and a knowledge of its volume is desired, but ordinarily 
the single tree is of interest to the woodsman only as it forms a part 
of a whole stand or forest. 
Factors that Affect the Accuracy of Estimates. 
Different methods of estimating the contents and value of timber 
have been developed in various parts of the country. These 
methods differ in degree of accuracy of results and each is designed 
for a particular region and set of conditions. Each timber cruiser 
has his own peculiar method of estimating the contents of a stand 
of trees. With many the general principle of procedure is the 
same, but the actual application varies. The reason for this is that 
accuracy is not so much a matter of method as of judgment, which — 
can be acquired only through practical experience and training. 
Therefore it is not possible to learn from books how to estimate 
timber, though a discussion of the various general methods of work 
should prove helpful. 9 
Standing timber nearly always contains defects. Allowance is 
made for these defects in various ways, but the cruiser must be 
able to detect the outward signs of defects, and, from his general 
knowledge, must decide what percentage of the timber is sound. 
The personal training of the cruiser also enables him to use his eye 
