DOTATION FOE N^ATIONAL EXPL'OirABILITI. 99 



manner throughout the forest, it may be traced to the character of 

 the soil, which may, for example,. be deficient in lime or rest upon 

 an impermeable sufa-soiL Such decay consists in the decomposition. 

 of the heart of tiie tree at- an early age. Actual experience 

 obtMned in working a forest can alone show whether the trees in it, 

 are affected, or not in this manner. 



The conditions of Qualitative Exploitability can be practically 

 realized only in the case of trees that are felled one by one, like the 

 standards of a compound copse and the trees in a forest worked by 

 Selection, whenever the object in view is to obtain -the highest sum 

 of Htility from each individual tree. In this case, the total produc- 

 tion' of the soil is not taken into account, either because it is of no 

 consequence, or because it cannot be estimated. Indeed the loss 

 of material that may result from the maintenance of trees that over- 

 top- others is slight, when such trees stand far apart ; for they too 

 produce wood and this wood is more useful by reason either of its 

 superior size or because it often belongs to more valuable species 

 t^an the overtopped trees. 



The age of maturity is very variable according to the species 

 concerned. It is rather late for the oak, the silver fir and the larch^ 

 and early for the beech,, the spruce fir and the Scots' pine. In any 

 case, without an examination of each individual tree and the poseesr 

 slon of professional experience. It is impossible for any one to say 

 whether a given, tree is in^ full growth, oris mature, or has beorua. 

 to decay. 



SECTION III. 



Rotation coeresponding to National. ExptoiiABiLiTY. 



The only way to obtain fr( m the soil the full amount of pro- 

 duction of which it is capable, and above all to employ every square 

 inch of it in the production of timber of large dimensions, h to rear 

 canopied forest. Hence in order to realize the highest sum of utility 

 possible, we must grow our trees in leaf-canopy and better still in 

 cinopied forest composed of trees of the same age, as far as that is 

 allowed by the nature and habit of the various associated species. 

 Now such a forest does not furnish the most useful produce it can, 

 yield until it is quite mature, whereas it returns the highest sum 



