20 



forest and for its height the growth durijig the exploitable- 

 age. If the exploitable age were doubled, the growing stock 

 would be represented, as in fig. 4, by a similar rectangle 

 of which the height (representing the growth) would be 

 approximately doubled : in other words, the growing stock 

 would be doubled. The produce removed would, however, 

 remain very nearly the same ; because although the coupes, 

 would be halved, their number (one for each year in the- 

 exploitable age) would be doubled. 



ISffcors. 



NoBMAL Geowing Stock OP 40 Years. 



The shaded portion represents the average annual increment for each coupe correspontf- 

 ing to a 40 years' rotation. 



