56 Forest Mensuration 



Trees growing as cones would grow, have C equal to 600; trees grow- 

 ing as Apollonian paraboloids would grow, have C equal to 800; after 

 Stoetzer, C might amount to as much as 930, in case of suppressed trees. 

 The minimum possible (in sound trees) for C is 400. 



The Pressler values given in the table of the preceding paragraph 

 closely correspond with the constant factors of increment ascertained 

 after Stoetzer. In the case of the Pressler table (at end of Paragraph 

 LXXXVII.) we find, for medium height growth and very small crown, 

 a factor 3.00 by which the diameter increment percentage is to be multi- 

 plied. This factor 3.00 corresponds with 600 for a constant factor of in- 

 crement. 



If the diameter in the midst of the bole is y 2 of the diameter at the 

 end, then the tree, it seems, is conical, and an increment factor of 600 

 might be assumed. If the sectional area in the midst of the bole equals 

 Yi. the sectional area at the end, then the tree is a paraboloid, and the 

 increment factor seems apt to be 800. 



It must be remembered, however, that a tree forming a paraboloid 

 grows as a paraboloid only, if its percentage of height growth is equal to 

 its percentage of growth of sectional area a rare case in merchantable 

 trees. 



Similarly, a tree growing as a cone must have the height increment 

 percentage equal to its diameter increment percentage. 



If n and v represent the number of rings per inch added to original 

 diameters d and 8 at chest height and at 0.45 of the height of the tree 

 respectively, then the "constant factor of increment C" is found as follows : 



400 C 

 p (volume) = 



nd 



nd 



C = 400 



PARAGRAPH LXXXIX. 



INTERDEPENDENCE BETWEEN CUBIC INCREMENT AND INCREMENT 

 IN FEET B. M. DOYLE. 



Doyle's rule under-estimates the contents of small logs and over-esti- 

 mates those of big logs. 



Consequently, the growth of a tree bole in feet b. m. Doyle is (for 

 small trees yielding logs under 28" diameter) relatively faster than the 

 growth of a tree bole expressed in cubic feet. The figures of Column D 

 denote, in the following table, this excess rate of growth : 



