144 THE MANAGEMENT OF WOODLANDS. 



If misused, however, this formula leads to absurd results, for the laud 

 and the growing-stock can be shown as having less than no value, if the 

 rotations for which the calculations are made are so low that the produce 

 is unmarketable and fails to counterbalance the cost of planting and 

 upkeep, &c. And the same happens if the rate of interest be high. 



For example, if a landowner has land suited for planting mixed Conifer 

 crops, and he wishes to estimate whether a rotation of 80 or 100 years 

 may be most profitable, he could reckon somewhat as follows with 

 whatever data he may think most reliable : 



1. Immediate Returns (Thinnings). Thinnings at 40 years worth 4, 

 at 50 years 5, at 60 years 6, at 70 years 7, at 80 years 8, and at 

 90 years 9. 



2. Final Yield (Mature Fall). Clear-felling at 80 years of age, 183 ; 

 or at 100 years, 266. 



The cost of planting being 5 an acre, the general charges for super- 

 vision, protection, and rates and taxes annually amounting to 5s. an 

 acre, and the rate of interest [being taken as 3 per cent, which would 

 prove the more profitable rotation ? 



(1) For the 80-years' rotation, the present value of the ultimate income 

 from all these future returns is 



183 + (4 x 1 -03 40 ) + (5xl -03 30 ) + (6xl -Q3 20 ) + (7xl -Q3 10 ) -(5x1 -Q3 80 ) -25 

 1-03 80 -! 0-03 



(183 + 13 -0480 + 12-1365 + 10 '8366 + 9 "4073) - 53 -2045T 



9-64 _T' 



~ 8-33 = 18-17 -8-33 = 9-84 = 9, 16s. 9d. per acre. 



[ 



(2) For the 100 years' rotation it would be 



\ +(9xl-03 10 )-(5xl-03 100 ) /__^- ' 



r03 loo -l 0-03 



f(266 + 23-5664 + 21-9195 + 19*5720 + 16-9911 + 14'4488 + 12-0951) - 96 -Q93Q~| _ , 

 1~ 18-22 ~J ' 



: 8 '33 = 15 '28 -8-33 = 6'95 = 6, 19s. per acre. 



18*22 



The 80-years' rotation would therefore be the more profitable quite 

 apart from its involving less capital and giving an earlier return from the 

 mature crop. 



Another example of this method of calculation may also be given, to 

 show its use for practical purposes. Suppose a Conifer working-circle of 



