582 JOURNAL OF FORESTRY 



In the region in which 32-foot logs are standard the volume tables 

 have been made accordingly. The difference in the length of the sec- 

 tions makes a good deal of difference in the scaled volume. For 

 example, where the taper per log is 2 inches, there is a difference in 

 the scale of two 16-foot and one 32-foot log of from 3 to IG per cent, 

 depending on its diameter. Hence it is important that the length of the 

 sections be syste iiatic, that it be as closely as possible coincident with 

 the Forest Service practice and that the system used be set forth in the 

 table itself. 



The Assumed Stump Height 



The height of stump which the volume table assumes is a minor 

 consideration, but is one which should be standardized for each set of 

 measurements and stated in the table itself. It is apparent that if in 

 making the table the volumes of the trees are so calculated as to include 

 the stem to a point 6 inches above the ground and the trees are actually 

 to be cut to a 23^-foot stump, an error in estimating of several per 

 cent will result. Other particulars in which standardization is necessarv 

 will undoubtedly occur to you, as, for example, whether it would be 

 feasible to construct tables that would take account of overrun, as 

 proposed by H. E. McKenzie. 



CONSTRUCTION OF TABLES 



After it has been decided what form our standard volume tables 

 shall take and what policies shall guide the selection of the trees to be 

 included in each table, the next matter to take our attention is the 

 method of making the table. You have probably all had a hand in 

 making a volume table or two by the conventional method, i. e., the 

 method of measuring a number of down trees, grouping the trees Ijy 

 diameter and height classes and securing the scaled volume of each 

 section, adding the trees of each group together and curving and 

 recurving the results. The striking thing about this method is the large 

 number of trees required to strike consistent and harmonized averages 



This is merely a method of comparing a lot of felled trees, which 

 are actually measured, with another lot of standing trees which are out 

 of reach. Its reliability depends on the principle of averages. 



If our volume tables were to be expressed in cubic feet instead of 

 in board measure, it is probable that some such formula as Schift'el's 

 (V = H (.16B -|- .66b) ) could be used to good advantage in measuring 

 the felled trees, because it is so much quicker than the laborious 



