DETERMINATION OF THE PROFIT. 157 



1. Determination of the Profit of Forestry. 



a. Calculation for the Intermittent Working. 

 In the case of a single wood of approximately uniform age, 

 the returns and costs do not occur at the same time, but at 

 intervals of various duration ; hence they must he calculated 

 for one and the same time. In the first place, that time shall 

 be the commencement of the rotation when the area is about 

 to be planted or sown for the production of a forest crop. 



i. CALCULATION FOR A BLANK AREA. 

 Let as before : 



Y r be the final yield occurring in the year r and again in 

 2 x r, 3 x r, and so on for ever ; 



T a , T b . . . T q , the thinnings occurring in the years 

 a . . . q, and again in a + r . . . q + r years, 

 again in & + 2 x r . . . # + 2 X r years and so on ; 



S c the cost value of soil ; 



E the capitalized annual expenses = - : 



'op 



c the cost of formation expended now, and again every 

 r years ; 



C the capitalized cost of formation = c - ---- ^ ; 



l'op r 1 



p the per cent, at which money can be made available for 

 investment in forestry, and at which money taken out 

 of the forest can be invested with equal security. 



Then the present value of all returns is represented by 



_Y r +Txl'op r - a +. . . 



l'op r -l 

 while the present value of all costs comes to ? 



S C +E+C. 



Hence the profit of forestry is expressed by the formula : 



Profit=P= r,+ T a x i-s^+._. + r. x i-^-- ( 



