THE FOREST PER CENT. 199 



made, say in the year x t its value with compound interest to 

 the year m + n must be added to W, so that the formula 

 becomes : 



cur. pr _ 1(?0 / 7 Y m+ n + T x X l-0p+ ' + S - E (l'O P n - 1) _ A* 



In either case the value 8 of the soil can be taken as the 

 cost value or as the expectation value. 



If n is placed = 1, the above formula reduces to : 



our. n _ (Y m+l -Y m -e)xWQ 



Pf - - 



agreeing with that given at page 163 for the current annual 

 forest per cent. 



Example. Taking the data in the table at page 122, and 

 putting p = 2J per cent., S = 250 shillings, e = 3 shillings, 

 the following values of pj> are obtained : 



For the period 70 80 years : 



log (100 +ft) - 2 + lQ g (218Q + 95 + 25 ~ B4) " lQ g (1592 + 250 > 

 7 -> / =2'86. 



For the period 80 90 years : 

 log (lQO+ ry )-2+ lo g (2695 + 94 + 250-34) -log (2130 + 250) 



The current annual forest per cents, given in the table 

 at page 202 have been calculated in this way, and they show 

 that the financial ripeness occurred during the period 80 to 90, 

 or more precisely in the year 82. 



* This formula differs from that given by Pressler and Judeich for the reasons 

 indicated in the footnote at page 163. 



