40 METHODS OF TREATMENT [CH. 



and might be advantageous, to have a floating block of approxi- 

 mately the same area, always formed of mature crops, most in 

 need of regeneration, but revised and re-constituted say every 

 ten years, so that at each decennial revision all areas in which 

 the regeneration was completed would be thrown out, and fresh 

 areas of the same extent fit for regeneration taken in. This 

 quartier bleu, as it is called in France, differs from the ordinary 

 periodic block in that it has not got to be regenerated during 

 a time prescribed, but is an area composed of all the compart- 

 ments in which regeneration fellings are to be either started or 

 continued during the time. Provided that the rate of progress 

 was suitably regulated by the prescriptions to determine the 

 annual yield, the whole working-circle would in this way be 

 worked through and progressively regenerated in a manner 

 offering great elasticity to silvicultural conditions, though with 

 a risk of some future disorder ensuing. 



It is evident that, unless there is already a fairly regular 

 succession of equal age-classes in the crop, the formation of the 

 complete series which is required for each self-contained periodic 

 block of equal area, will not readily be obtained, and in order 

 to equalise the areas of the blocks it may be necessary, on ac- 

 count of its enforced topographical position, to include in one 

 periodic block a compartment which, from the point of view of 

 its age, ought to be placed in a different block. In such a case 

 this compartment might have to be regenerated in a period other 

 than that corresponding to the block in which it is of necessity 

 placed. Absolute uniformity is not to be expected at any rate 

 until the second rotation. Then with regard to the internal sub- 

 division of these periodic blocks, it is only in very exceptionally 

 favourable circumstances that regular equal annual coupes can 

 be laid out. The reason for this is that the regeneration does not 

 proceed like clock-work, and that the successive regeneration 

 fellings will necessarily depend for their progress on the gradual 

 development of the young crop which is being created. 



Good seed-years may only occur at infrequent intervals, and 

 the regeneration must necessarily depend on cultural conditions, 

 and cannot be forced. The yield therefore is nearly always 

 regulated by volume, based on the cubic contents of the old 



