6 FIRST PRINCIPLES [CH. 



standing, and fully stocked, up to the standard imposed by the 

 local conditions of soil and climate. 



Just before the loo-year-old acre of forest in the above 

 example is felled, this acre may be regarded as the interest on 

 the capital formed by the 99 acres of growing stock. Just as 

 money deposited in a bank produces annual interest, so does our 

 wood-capital standing in the forest. Instead, however, of har- 

 vesting each year the annual production of each acre of the 

 forest, we realise each year the accumulated production (e.g.) of 

 100 years on one-hundredth part of the whole area; and we can 

 only continue to do so permanently, if we maintain a complete 

 and unbroken succession of all age-classes, each occupying an 

 equal area, always standing and in active growth. See the 

 figure on page 9. 



It is evident that the longer the rotation, the greater will be 

 the wood-capital or growing stock which it will be necessary to 

 maintain. If, for instance, in the above example we were to 

 make 200 years our rotation instead of 100, it is obvious that the 

 volume of our wood-capital would have to be doubled, although 

 the annual yield (200 years accumulated production over half 

 an acre) would be much the same as before. 



In systematic forestry therefore, where a sustained annual 

 yield is desired, it is necessary to keep a very large volume of 

 timber, covering a large extent of land, and representing a large 

 amount of invested money, always standing on the ground. This 

 graduated series of age-classes over equal areas is of course an 

 artificial condition, and it may take as many years to constitute 

 this wood-capital as there are years in the chosen rotation. The 

 importance of the time element in forestry is thus easily felt, and 

 the necessity for continuity of management is at once seen. 



Without this continuity of management no organised forestry 

 is possible, and that is one reason why working-plans have been 

 generally confined to forests belonging to the State or other 

 corporate bodies, in which some continuity is assured. 



With private owners there is no assurance of continuity from 

 one generation to another, and therefore the necessary organised 

 growing stock is seldom, if ever, constituted, and systematic 

 working is hardly possible. 



