592 



lOURNAL OF FORESTRY 



Applying the taper figures given to the Jonson formula/ one finds 

 that thj tree's form class is 0.(J90. The Jonson tables give for a tree 

 9 inches d.b.h.. height 50 feet, and form class 0.090, a volume of 11.^5 

 cubic feet as compared to the 11.36 given by Zon. 



Balsam in Maine. (Same Bulletin) : 



D.b.h. 13 inches, height 80 feet, total \olume is 0.368 cords per tree. 

 One cord for such a tree contains 98 cubic feet. Total volume is, 

 therefore, 36.10 cubic feet. 



Doing as before, one finds such a tree's form class to be 0.663. 

 Jonson's tables give for a tree 13 inches d.b.h., height 80 feet, and 

 form class 0.663, a volume of 35.95 feet as compared to the 36.10 

 cubic feet given by Zon. 



Taking data given by William Dent Sterret in Bulletin No. 820 on 

 Jack Pine, a jack pine of given d.b.h. and height are shown to have 

 certain taper series. Obtaining their form classes as before (or even 

 graphically, especially if root swelling extends up to breast height), 

 one finds the comparison between the Sterret and the Jonson series 

 in Table 1. 



Table 1 — Diauiclcr in Indies at Different Heights Above the Ground. 



d , c-^h 



* The formula used by Jonson was the Hojer equation: p= C log ^ 



where "d" is the diameter at any point above the d.b.h., "D" = d.b.h. C and c = 



, , total height — height of d 



constants and h =: — ,— ,— . t -, , — ^-r- 



total height — breast height 



Root swelling must be graphically eliminated, otherwise too high a form class 



will result. 



