60 THE WHITE PINE 



A the basal area of the whole class, and 

 a the basal area of the test tree, then 



V : V : : A : a 



or F= 



a 



If, for example, a major class containing 

 trees of 11, 12, 13, and 14 inches in diameter 

 has a total basal area of 500 square feet, and 

 its test tree has a basal area of 1 square foot 

 and a volume of 25 cubic feet, then 



= the volume of the whole class. 



The content of each major class being thus 

 determined, their sum gave the contents of the 

 whole group. In this way the total volume of 

 each group, with and without bark, was ascer- 

 tained, as well as the merchantable contents in 

 cubic and board feet. Here, as in all calcula- 

 tions of volume in this study, branches were 

 entirely excluded. 



