640 SCIENCE PROGRESS 



be the object of the forester to remedy these conditions. In 

 the case of the light-demanding crop, this is best done by 

 underplanting with a shade-bearing species, preferably the 

 soil-improving beech, which will preserve the condition of 

 the soil and prevent the growth of weeds, and in the case of 

 shade-bearers the same treatment may be applied when, after 

 the chief height growth is completed, a heavy thinning is made ; 

 or the thinnings may be regulated to produce similar results 

 without underplanting. In either case failure to treat the 

 crops as described may preclude the possibility of natural 

 regeneration, or at any rate may so prolong the period of 

 regeneration that the expedience and economy of the method 

 will be doubtful. 



Finally the question of rotation has to be considered. In 

 the case of the common conifers the best financial results are 

 generally found to be obtained when the final crop is removed at 

 an age of from 75-90 years, while in the case of oak 120 years, 

 and in the case of beech 80-100 years may be taken as average. 

 It is impossible accurately to fix the best rotation when a crop 

 is first established, indeed, it is unnecessary to do so. The 

 financial rotation is the only one properly employed in 

 economic forestry, and this depends chiefly on the growth 

 of the crop and the demand for various classes of timber. 

 This rotation corresponds with the age at which after calcu- 

 lating all revenue and expenditure at a fixed rate of compound 

 interest the largest surplus or soil value remains. Practically 

 it is best determined by means of the " Weiser-prozent " which 

 may briefly be stated to be the rate of interest which at any 

 given time a crop is producing on the capital it represents. 

 The rate of interest fixed for the working capital has con- 

 siderable influence on the rotations so determined, and 3 per 

 cent, is most suitably employed. 



Indisputable as the necessity for such a sound financial 

 basis may seem, it is curious that there are still supporters 

 of methods having as their object the maximum annual returns 

 regardless of cost, and that in the United Kingdom there are 

 advocates of afforestation with the chief object of producing 

 pit timber. The demand for this commodity has greatly 

 increased, but the increase in the price is not in proportion 

 to that for other coniferous timber, thus showing the supplies 

 to be less restricted. This, indeed, is to be expected, seeing 



