ROTATION OF THE HIGHEST INCOME. 201 



If a change of rotation has been decided on, it can be carried 

 out at once, provided the forest is of small extent and the 

 demand for produce sufificientl_y large to absorl) the extra 

 supply of produce thrown upon the market, without causing 

 any appreciable change in prices. If the forest is, however, 

 of some extent and the demand for produce uncertain, it is 

 always desirable to make the change gradually, so as either 

 to spread the extra supply of produce over a number of years, 

 or to accumulate the extra growing stock gradually, thus 

 disturbing the market as little as possible. 



2. Rotation of the Highest Income. 



By this is understood the rotation, which yields the highest 

 income, calculated without interest and irrespective of the 

 time, when the items of income occur. The net income is 

 thus calculated according to the arithmetical mean of incomes 

 diminished by the costs. All items of income and costs during 

 one rotation are added up and the sum of the latter deducted 

 from the former ; the difference, divided by the num])er of 

 years in the rotation, represents the mean annual income. 



Hence, the rotation in this sense is that, under which the 

 expression — 



Annual income = y,- + T„ + T„ + . . + T,, - r - y x e 



r 

 becomes a maximum. 



This rotation falls, as a rule, a considerable number of years 

 beyond the financial rotation. 



Example. — Taking the data contained in the table at page 

 120, the net annual income amounts to — 



For a rotation of 



Shi/Ji,)' 



2,187 + 5 + 44+87 + 118 + 184-00- 



70 years = '^^^ = 38 



70 



2,860 + 5 + 44+87 + 118+184 + 144- 



80 years z. ^^'^^X^ =39 



80 



