180 STANDARD VOLUME TABLES 



The deduction of a given per cent for cull would ruin the table, making 

 of it a local table applicable only to timber which is assumed (one can 

 never know certainly) to show the given per cent of defect. Even if 

 the per cent of deduction is stated, the table would require complete 

 recalculation for stands varying from this per cent of cull. By contrast, 

 tables made for sound trees permit of the calculation of total volume 

 for trees or stand, after which the estimated per cent of cull may be 

 deducted from this total. 



All volume tables should be constructed to show only the volume 

 of trees as if sound. They are based on exterior measurements or 

 form, without deduction for interior defects, which must alwaj's be made 

 b}' the cruiser from observation of the character of each separate tree 

 or stand. 



152. Conversion of Volume Tables for Cubic Feet, to Cords. As 

 seen in Chapter IX the ratio of cubic to stacked volume increases with 

 the diameter, straightness and smoothness of the average stick and vice 

 versa. Tables of cubic volume may be converted into cords by the 

 use of ratios or converting factors, but if a constant ratio is used for 

 trees of all sizes, the corded or stacked contents of small trees will over- 

 run the values shown, while that of the larger trees will fall below it. 

 Fixed ratios, of which 90 cubic feet per cord, or 70 per cent is an example, 

 have the merit of standardizing the cubic or solid contents per stacked 

 foot for trees of all sizes, regardless of their actual stacked volume. 

 By mixing the cordwood from large and small trees, the average ratio 

 might be attained in practice. The best example of this principle is 

 the Humphrey caliper rule, which converts cubic to stacked measure 

 by the ratio of 100.5 cubic feet per cord or 78.5 per cent. If this principle 

 is adopted, the volume for each tree class is divided by the number of 

 cubic feet per cord, which converts the table to the form desired. 



Where actual stacked volume is desired for trees of each size, the 

 ratio of conversion must be found separately for the different size 

 classes. The tree, and not the bolt of cordwood, is the unit to be meas- 

 lu-ed, hence the average size of the cordwood from trees of different 

 sizes determines the converting factor. But few tables have been pre- 

 pared on this basis. The most satisfactory method is to stack the cord- 

 wood from trees of different diameters separately and determine the 

 factors directly. A simpler method is to determine the diameter of the 

 average stick in the tree, and apply the ratio previously found to hold 

 good for cordwood of this average size. 



The ratio or ratios used for conversion should always be shown 

 in connection with cordwood volume tables. 



An example of the converting factors used in constructing cord wood volume 

 tables for second-growth hardwoods is given in Table XXXII. 



