ALLOTMENT DURING THE REGENERATION PERIOD. 49 



Hence 



Increment on old stock = 



f m-1 

 l^T X 



m_(m-l)xl_mx I __ I 

 2~ ~~2~ 2" 



Increment on new stock = 



1 j j \m_ _mx I , I 



m J 2 ~" 22' 



If the first cutting is made at the end of the first year, then 

 the position is reversed, and 



Increment on old stock = - + 



mx I I 

 ,, new ,, = - . 



For the middle of the growing season 



Increment on old stock = 



2 



I . - ,, n ew =^. 



For all practical purposes the same result is obtained, pro- 

 vided m is not too long, by adding to the existing old growing 

 stock half the increment which it would have laid on in the 

 course of m years if no cuttings were made, in other words 

 placing the expected yield equal to the volume of a wood, the 



final age of which is increased by -^ years. 



What has been said above, enables the forester to calculate 

 the annual yield which a wood under regeneration gives during 

 the period of m years, namely : 



mxl 



Annual yield = ^ = ^f + 3- 



Again, if the yield = Y has been fixed, the number of years 

 during which the wood under regeneration will give that yield, 

 can be calculated : 



