FOREST ECONOMY. 215 



likely to rise, as natural supplies are exhausted, and 

 the demand for the better soils for agricultural use 

 limits forest growing to the poorer, absolute forest 

 soil. Forest properties, with the exception of the 

 danger from fire, which will be greatly reduced 

 when systematic management is begun, are in 

 general safe properties and easily managed, requir- 

 ing little labor. Hence, if safe long time invest- 

 ments in the United States, such as savings and 

 trust'companies favor, are bringing now only 3 and 

 3 \ per cent, it is justifiable to use no higher, pos- 

 sibly a lower, interest rate in forestry calculations. 

 If now we inquire what the " soil expectancy 

 value," i.e. the value of the soil expressed by its 

 expected yields, is, and how it is calculated, we 

 must first conceive that every stand in a regulated 

 forest management is expected to be harvested 

 every r years (years of rotation) forever ; the 

 income is therefore in the nature of a periodic 

 or intermittent interminable rent or revenue (R\ 

 the capital value of which at present (C ) being 

 found by well-known mathematical methods in the 



r> 



expression C n = z The rent or revenue 



i o/ r i 



is composed of the final harvest yield ( F r ), and of 

 intermediate incomes by thinning (7"), occurring in 

 the years a, b, etc., the values of which have to be ex- 

 tended for purposes of comparison to the same time in 

 which the harvest yield occurs, namely to the year r. 

 The expenditures which have to be offset are the out- 



