148 UNITS OF MEASUREMENT FOR STANDING TIMBER 



Combination Volume Tables giving the merchantable volume in 

 Ties, and residual cords. 



Board feet, and residual cords and other combinations. 

 Graded Volume Tables, giving the volume in 

 Board feet, by lumber grades. 

 Logs, by log grades. 



The use of the last-named tj'pe has not yet been attempted. 



Volume tables of this character make possible the tallying of every 

 tree, eliminate the risk of averaging the dimensions or volume of trees 

 counted, and require of the cruiser only the recording of diameters 

 and of heights, and discounts for defect. 



Since trees vary so widely in form, height and taper, and the table 

 is implicitly relied on to give correctly the variable volumes caused 

 by these factors, without measuring the taper, the use of such tables 

 and their reliability or accuracy must be thoroughly understood, or 

 it may easily lead to errors of greater magnitude than those incurred 

 by an experienced cruiser using the universal " taper " table for volumes 

 (§ 149). 



The greatest drawback in the use of specific volume tables is the 

 number of tables required, and the cost of their preparation. Species 

 may differ from each other in form or bark thickness, so as to require 

 separate volume tables. Substitution of a table made for one species 

 for use with a different species is justifiable only when research has 

 shown the two species to possess the same bark thickness and average 

 form. 



Tables made for one unit of measure, or even for a given log rule 

 are not serviceable for a different unit or log rule. Tables of merchant- 

 able volume, accurate for a given standard of tree utilization, become 

 obsolete when a closer standard is adopted. For these reasons, and 

 owing to the great number of species, range of conditions, difference in 

 log rules, and variety of products, the cruiser entering a new region 

 is usually confronted with a lack of tables, and is driven to adopt 

 either the universal taper system, or the log, as his means of estimating 

 volumes. The adoption of a universal cubic-foot basis for volume 

 would greatly simplify the problem of volume tables. 



125. The Point of Measurement of Diameters in Volume Tables. 

 Either of the above types of volume table shows volumes for trees of 

 given diameters and heights. The diameter must be measured near 

 the base of the tree, where it can be reached with calipers or tape. 

 But there is no regularity about the flare of the butts of trees, for this 

 is determined by exposure to wind strain, by the size of the bole, the 

 site and the species. Butt swelling increases more rapidly with age 

 than does the diameter of the bole, so that the older and larger the tree, 



