10 SYSTEMS AND UNITS OF MEASUREMENT 



table, which gives the average contents of entire trees of different dimen- 

 sions, in terms of standard log rules or other units, tlius eliminating a 

 certain amount of ocular work. 



17. Need of Standardization for Both Commercial and Scientific 

 Measurements. The justification of the use of standards which give 

 the contents of standing timber in terms of products, rather than 

 actual cubic volume, lies in the fact that the value of the timber, standing 

 or cut, depends upon the volume and quality of these products and not 

 upon the cubic volume. 



Had it been possible to secure the adoption of a uniform standard 

 of conversion into board feet, the use of this standard would be more 

 serviceable than the apparently simpler cubic standard. But in prac- 

 tice the same motives which here gave rise to standards based on products 

 have led the French to adopt, as substitutes for cubic measurement, 

 rules of thumb which are less accurate by far than many of our log 

 rules. ^ 



The greatest drawback to the use of units intended to measure 

 the product directly lies not in their character but in their inaccuracy 

 and in the multiplicity of standards. It is easily seen that volume 

 tables and measurements of growth which are based on some widely 

 used commercial log rule may coincide with custom, but are incapable 

 of use or comparison with other log rules (§ 77) and are inaccurate as 

 a scientific basis of measuring growth or volume. This fact has led to 

 endless duplication of effort and has been the chief reason for the lack 

 of real progress in accumulating standard data on volume and growth 

 of American trees. 



A continuance of such duplication of effort will hinder the progress 

 of forestry in America, which must depend in a large part upon the 

 accuracy of volume and growth data gathered by forest measurements. 

 While the local value of data based on log rules sanctioned by custom 

 will continue, these field data should be gathered in such form as to be 

 of permanent value independent of these variable local standards. 



It is possible to convert all measurements to the common standard 

 of cubic feet, which gives a basis of scientific comparison between the 

 volumes of different trees and species, and a permanent basis for measure- 

 ment of growth for trees and stands. It is also possible to adopt, for 

 the purposes of permanent record, a log rule based on scientific principles 

 which will give an equally reliable comparison of the contents of trees in 

 board feet and the growth of stands expressed in this unit of product. 



But for a permanent record from which the volumes of trees may be 

 derived in any unit of product, standard or local, the average form of the 



1 Mensuration in France, Donald Bruce, Journal of Forectry, Vol. XVII, 1919, 

 p. 686. 



