NATURAL HISTORY OF THE FOREST. 163 



trees which participate in the upper crown level, 

 and the volume of the whole stand may then be 

 closely approximated by multiplying this amount 

 by the number of trees involved : 



(vol.ofstand = ;.x 3"^^--^- + 7min. > 



If the trees are arranged in size-classes from the 

 stoutest down, the average tree will be found to 

 be at about 40 per cent from the stoutest. For 

 instance, in 500 trees, the 200th tree, counting from 

 the stoutest, will be the average tree. Moreover, if 

 these trees arranged in size-classes are divided into 

 five groups, the first fifth will contain 40 per cent 

 of the total volume, the second fifth 24 per cent, 

 the third 17 per cent, the fourth 12 per cent, and 

 the last, the slimmest, will represent only 7 per 

 cent of the total volume of all the trees. 



These interesting deductions from the yield 

 tables, which could be multiplied, are cited merely 

 to impress upon the reader the fact that the forest 

 grows under the influence of recognizable laws, 

 just as the single tree does. If we differentiate 

 the volume into the different sizes of material, 

 logs of given diameter, cords of certain character, 

 etc., expressed in quantities or relative proportions, 

 and apply market prices, we can come to a concep- 

 tion of the value accretion of a stand at any par- 

 ticular time, and then can discuss upon a tangible 

 basis the results of a forest management which 

 may change at will the growth conditions and de- 



