104 



The formation of the working-circles is not a matter of 

 difficulty. A correct gradation of ages is by hypothesis 

 unobtainable. The duration of the provisional plan for the 

 transformation of the forest would be equal to the exploit- 

 able age of the forest which it is sought to constitute, and 

 would be determined in the same way, that is to say, it 

 would depend on the size of the exploitable trees and on the 

 rates of growth. The periodic blocks would consist of a few 

 great natural divisi('Vis of the forest, chosen so as to furnish 

 more or less equal material during corresponding sub-mul- 

 tiple periods of the exploitable age. Indeed, the general 

 scheme is usually very obvious and well defined. When it 

 has been thus drawn up, two classes of operations will be 

 required, namely, (1) transformation fellings in those 

 portions of the forest which are to be first regenerated, and 

 (2) modified selection fellings elsewhere. 



The transformation fellings do not usually differ very 

 materially, at least in principle, from ordinary successive 

 regeneration fellings; but their execution will depend more 

 markedly on the nature of the crop, and it will be necessary 

 to change the manner of applying them from place to place 

 according to the irregularities met with. Where reproduc- 

 tion is abundant, they will simply remove the mature trees 

 in whatever way is required, so as to leave room for the 

 young growth to develop. Where there is little or no young 

 growth already established it will be sought to obtain 

 reproduction in the ordinary way by successive fellings, 

 preparatory or seed, secondary and final. The selection 

 fellings to be carried put in the blocks to be regenerated 

 later on offer no difficulty. The trees to be removed will be 

 such as cannot maintain themselves in a sound state until 

 the crop in which they grow reaches its turn for regeneration. 

 Knowing the length of the rotation and the rates of growth, 

 the question is easily determinable. Thus, where the ex- 

 ploitable size of the trees is 24 inches in diameter, with 

 a rotation of 120 years, and a rate of growth of 10 years for 

 each inch of radial increase, all trees above 12 inches in 

 diameter might be felled in blocks or coupes in which re- 

 generation fellings will not be made during the following 

 60 years; while in those blocks which will come under 

 regeneration in, say, 30 years, only absolutely unsound trees, 

 or at any rate trees well over 18 inches in diameter, would 

 be felled. The selection fellings would in other respects be 



