VON MANTEL S METHODS. 



99 



class being multiplied by a volume factor representing the timber 

 content. The following note examines the application of standard 

 formulae to ^uch conditions, for ascertaining the yield of the 

 whole forest. The principal formulae are (1) Von Mantel, (2) 

 Heyer, (3) Hufnagel, (4) Karl or C. A. I. As these formulae 

 are fully discussed in all text-books (e.g., Schlich and Eecknagel), 

 it is only proposed here to explain why and how they must be 

 modified to suit conditions given above. 

 Von Mantel's formula is 



Y_1Z. / V=real growing stock | 

 1 ' r=rotation. J 



Now this formula is theoretically correct only if V represents 

 the whole crop down to seedlings and the wood volume of each 

 tree measured down to 0" diameter. Practically of course this is 

 impossible anywhere in the world, but by measuring trees and 

 wood down to V or 2* diameter we get a sufficiently close ap- 

 proximation. However by measuring trees and wood down to 

 such a high limit as 8", a very serious error is introduced, which 

 will be evident from the following : 



Consider three cases (all for a normal series of age gradations) 

 (a) trees and wood measured to diameter 0" ; 

 (6) trees and wood measured to a diameter equal to \ rota- 

 tion diameter (or diameter \ for short) ; 

 (c) trees and wood measured to a diameter corresponding to 

 an age X (or diameter X for short, in India usually 

 8'"). 



(a) 



Von 



Mantel's 



method. 



Obviously V = A aor 



