31 



tiandj tho capital is insufficient, as in fig. 2 for instance, or 

 superabundant, a quantity of material, less or greater as tlie 

 case may be thau the average increment, must be felled 

 during a certain provisional period until the normal state 

 is reached. 



A forest of 20 acres, whicli it is proposed to exploit as coppice at 20 years, is 

 found to contain a complete series of growths of all ages from I to 20 years, each 

 occupying one acre. Here the possibility would evidently be a crop 20 years old 

 rgrowing on one acre {vide fig. 1). If, however, the crop were constituted as shown 

 in fig. 2, it would be necessary, in order to obtain a sustained annual yield of 

 wood not less Ihau 20 years old, to make the two crops of 19 and 20 years last for 

 some 10 years, until the crops now 10 years old have attained or approached 20 yf ars 

 -of age. The possibility in this case might be fixed during the provisional period as 

 the orop growing on two-tenths of an acre per year, after which it wonld be in excess 

 of the normal possibility, or certain areas might be cut oyer when the crop was more 

 than 20 years old nntil the necessary gradation of ages (fig. 1) could be secured. 



3. Methods of prescribing the possibility.— As it is impossible 

 to collect the annual production all over the area, it is neces- 

 sary to prescribe the realisation of the possibility in some 

 practicable manner. The realisation of the possibility can be 

 prescribed in three ways, viz., (i) by M'ea, {ii) by number 

 of trees, and (iii) by volume of material. The first method 

 is the simplest and is that followed in the case of coppice 

 fellings, the method of clearances, as well as partly in the 

 selection method of fellings regulated by cultural rules. 

 The nu'nber oE trees to be felled is prescribed in the case of 

 standards over coppice and in the selection method : and 

 also in the uniform metbod. It is only in applying the 

 method of successive regeneration fellings and, more rarely, 

 in the selection method, that the volume of material to be 

 felled is prescribed. In actual practice, however, in addition 

 ;to prescribing the quantity of material the areas in which 

 the fellings are to be made are also prescribed. Practically, 

 therefore, what is prescribed is the felling on a given area 

 ■of either the crop, a stated number of trees, or a given 

 Tolume of material. 



But in whatever way prescribed, the realisation of the 

 j)ossibility should be formulated in a sinaple manner, easy to 

 .apply and to control, and so that it constitutes of itself the 

 main provision of the working-plan. 



A rule such as the following would fulfil this condition : — 



" Bach year there will be felled, by the selection method in successive annual 

 coupes of one-tenth of the total area, a number of trees not exceeding 700, in the 

 proportion of 4 firs to 3 oaks." 



Or, were the number of trees not prescribed and were the fellings limited by 

 sylvicultural rules, and possibly, in addition, by the provision of a maximum volume 

 of mateiial, the rule might be to the following effect : — 



" There will be -felled, on one-tenth of the area each year, all dead, diseased or 

 <lamaged stems 1 and stems that it is otherwise desirable, for sylvicultural reasons, 



