122 FORESTRY 



9 feet, i 5 feet, etc., along the stem. The volume of each 

 piece is calculated as the product of the middle sectional area 

 multiplied by the length. All the volumes added together 

 give the total contents of the stem. The topmost portion is 

 measured apart from the rest of the stem as partaking of the 

 nature of branchwood. 



Measurement of a standing tree. The volume of a standing 

 tree for any given species and age may be found by means of 

 form-factors 1 (factors of shape). First of all, the diameter of a 

 tree should always be taken at breast height, or, to be exact, 

 at 4 feet 3 inches from the ground. The diameter being 

 taken at this point, the area of a cross-section is found, and the 

 tree's height measured. The volume is then the product of s 

 (area of the cross-section) x h (height) xf (form-factor). By 



form-factor is understood the quotient , where v is the 



s x h 



volume of a stem or of a whole wood, and / and h are as 

 before. A form-factor reprWents 

 the relation of the tree's volume 

 to the volume of a cylinder whose 

 basal area is the same as the area 

 of a cross-section of the stem at 

 4 feet 3 inches from the ground, 

 and whose height equals the total 

 height of the tree. The principle 

 is illustrated in Fig. 28. 



Of the various methods by 

 which the present volume of a 

 wood may be ascertained, form- 

 factors and volume tables are 

 most generally employed. In 

 using form-factors, all the trees 

 in the wood are callipered at 



1 In Germany three kinds of form-factors are recognised : Tree 

 form-factor (Baumformzahl], representing all wood upon the tree. 

 Timber form-factor (Derbhol%formzahl} = z\\ timber having a diameter 

 of over 7 cm. (nearly 3 inches). Stem form-factor (Schaftformzahl} = 

 timber over 7 cm. upon the stem only. 



I / 



FIG. 28 



