FACTORS OF FOREST PRODUCTION. 109 



slowly in their youth, then increase in their rate, 

 continuing for a long time in an even, rapid devel- 

 opment, then persisting at a slower but uniform 

 rate to an old age. 



If we were to utilize these latter as soon as they 

 reach useful size and then renew the crop, we would 

 again and again repeat the period of slow growth, 

 and hence lose in relative quantity of production. 

 If, on the other hand, we allowed the soft woods 

 mentioned to grow beyond the stage of rapid 

 growth, we would lose equally at the other end. 

 The study of rates of growth of species and of 

 quantitative production of stands of different 

 species, the mathematics of forest growth, the 

 results of forest mensuration, is so important a 

 matter that we devote to it a special chapter. 



Here we only wish to point out that, among the 

 factors of production, time plays a much greater 

 r61e than in any other business, and in fact influ- 

 ences the use of all other factors of production and 

 methods of procedure to such an extent, that, if 

 forestry be carried on as a business by itself, its 

 conduct becomes in many respects sui generis. 



The time when the crop is ready for the harvest, 

 it will be apparent from the above considerations, 

 is not a matter of natural period as in the ripening 

 of fruits, but depends not only upon many com- 

 plex considerations, varying with species and soil 

 and climate, but upon market conditions, econom- 

 ical considerations, and industrial requirements, and 



