24 



2. Calculation of the volume of the normal proving stock — If 



"i" represents the mean annual increment laid on annually 

 by each of the "r" age-gradations corresponding to the 

 number of years (r) in the rotation, tbe normal growing stock 

 would be (calculating for the end of tbe growing season, 

 immediately before tbe annual felling is made) — 



i + 2i+3i+. +u 



= (ri+i)| 



2 ^2 



wnere I (=ri) represents the growing stock on the oldest 

 age-gradation, as well as the total increment laid on by all 

 the age-gradations during one year {see fig. 3). Or, neglect- 

 ing tbe term |, the normal growing stock may for all 

 practical purposes be taken as=lx|; 



F,g.3, 



GROWTH^ 

 ?0 Ve^rt 



UVe>r 



20 19 18 1/ 16 15 14 10 12 H 10 8 8 7 6 5 4 3 £, I 

 t«-— -- ■ " ' r . — '^ ARtA8 



NoBMAL Gbowinq Stock ob 20 Ybabs. 



The sTiaded portion re resents the average annual increment for each coupe correspond- 

 ing to a 80 years' rotation. 



