HATATION IGB, CO^SIMEECIAl EXPLOITABILITT. 103 



•yiel3sno money return except once after a more or less long series ©f 

 years. The income derived from and the capital sunk in the forest 

 do not increase in the same ratio as the years go on. The question to 

 resolve is, therefore, the determination of the age at which the forest 

 should be exploited in order to obtain from it the largest income 

 compared with the capital invested. 



This problem is capable of a single general solution, and also 

 presents some very important special cases. The general solution 

 is. applicable to woods composed of trees of the same age, such as 

 ■dimple copses and all perfectly uniform canopied masses of trees^ 

 The most important particular cases are those presented by the 

 standards of a compound copse and forests worked by Selection. 



§ 1, Rotatiun <applicable to a Wood composed of Trees of 

 Uniform Age. 



f 'Given a compartment of average fertility — if not a compart- 

 ment, say a coupe or even an acre of forest ; the problem before us 

 is simply to determine the -age at which the crop standing on this 

 area ought to be cut. This will also be the age for exploiting the 

 other coupes or portions of the "Working Circle, that are placed in 

 the same conditions of production. Thus this age is itself the rota- 

 tion sought. The procedure to follow depends on the following 

 proposition : — 



The revenue derived from, the exploitation of a uniform cano- 

 pied forest is necessarily periodic, and increases for every year that 

 the forest is allowed to stand. The revenue for each year represents 

 the p.mount of interest on a certain definite capital, calculated at the 

 customary rate of interest expected from investments in forest pro- 

 perty. The capital corresponding to each year's revenue, therefore, 

 increases from year to year like the revenue ; and hence the most 

 profitable revenue, i. e. the age of Commercial Exploitability , corres- 

 ponds to the largest resulting capital. 



In order to find the age at which a given forest composed of 

 trees of the same age becomes commercially exploitable, we must 

 first of all determiae the various figures of the respective receipts 

 obtainable at regular periods for a series of years ; then by a simple 



