52 Forest Mensuration 



or radii as abscissas. The scale for the height entries should be much 

 smaller than that of the diameter entries. 



Diameter points, at the different section-heights, corresponding to a 

 given decade of years are joined (beginning at the outside), by which 

 procedure the outline of the tree at that decade is established. 



Th top cones are obtained by prolonging such outlines arbitrarily until 

 they intersect with the height-axis. 



The merchantable bole for each decade is dissected, on the diagram, 

 into logs the length and diameter of which are measured on the diagram. 



PARAGRAPH LXXXIV. 

 WAGENER'S METHOD AND STUMP ANALYSIS. 



Wagener recommends a partial stem analysis for cases in which a 

 knowledge of the absolute increment, not a knowledge of the absolute 

 tree volume, is required. Tree volume is sectional area chest high times 

 height of tree times form factor. 



Wagener analyses : 



a. the height growth by counting the rings at various altitudes along 

 the bole; 



b. the growth of the sectional area at chest height by measurement in 

 decades in the usual way. 



Wagener then estimates the form factor according to form factor tables. 



In the latter proposition, obviously, lies the danger of mistakes. Since, 

 however, increment is a difference of volumes, merely the difference of 

 mistakes a comparatively small item enters into the problem. 



The "stump analysis" (compare Paragraph LXXII.) introduced by 

 the Bureau of Forestry rests on premises similar to those proffered by 

 Wagener. 



If the form height for the stump-diameters (or the number of feet 

 b. m. per square foot of stump area for given stump diameters) is known, 

 the rate of volume increment can be quickly ascertained by mere stump 

 analysis. 



