186 FARM FORESTRY 



by averaging together the contents of all of them. The accu- 

 racy of the estimate will, of course, depend on the skill used 

 in picking out the average trees. 



With very large tracts of timber volume tables are used 

 instead of log tables. These give the contents of trees in board 

 feet when their heights and diameters are known. All the 

 trees on the tract can be estimated or only those on sample 

 acre plots or on measured strips run in parallel directions 

 across the tract. Volume tables for several species will be 

 found in the Appendix. Many others are given in the Wood- 

 men's Handbook, Bulletin 36, U. S. Forest Service, and in 

 books relating to general forestry. 



ESTIMATING A SMALL WOODLOT FOR CORDWOOD 



In estimating a small woodlot for cordwood each tree is 

 estimated by itself, as in the case with board feet. When a 

 tree has been estimated it should be marked in some way 

 so that it will not be considered a second time. If all the 

 trees are marked on the same side it will be easier to keep 

 track of them. 



To obtain the cords of wood in a woodlot the cubic feet 

 contained in all the trees are first found. The total cubic 

 feet in the trees divided by 90, the average number of cubic 

 feet of solid w r ood in a cord of wood, will give the estimate 

 of the number of cords of wood in the woodlot. 



The number of cubic feet in a tree including the larger 

 branches is found, as already explained, by considering the 

 entire tree as a cone with slightly bulging sides and finding 

 the volume in cubic feet by multiplying the basal area in 

 square feet corresponding to the diameter of the tree measured 

 at breast height by one-half the total height of the tree in feet. 



The diameters are measured accurately to tenths of inches 

 outside the bark, for the whole tree is used for cordwood. If 

 a tree is not perfectly round the average of the largest and 



