THE FOREST PER CENT. 197 



W W X l'0p v * X I'op* X l'op, n ; 



or 



or 



-l .*g* . g g , 



100 100 2 100 3 



or 



100 2 



In this equation the right side expresses nothing else than 

 the current per cent, with which the forest capital w works 

 during the period of n years, in other words what has been 

 called at page 163 the current annual forest per cent. The 

 proof is easy : If n = 1, the original formula becomes : 



W=w (l'op v ) (l'op q } (l'op s ) 

 and also : 



W=w (1-op,). 

 Hence 



l-op f =(l-op v ) (l'op q ) (rop 8 ) 



and 



, -L V +*, + qv sy s, 



100 



Hence the above formula can be written thus : 



This formula was introduced by Pressler, who called 

 the cur pf thus obtained the indicating per cent. (Weiserpro- 



