104 



introduced in the manner of verifying the possibility and in 

 graduating the age -classes. These modifications are, however, 

 too complicated for adoption in this country, where indeed 

 the method is not generally suitable in present circumstances, 

 owing to its complicated nature, its uncertain results, the 

 frequent revisions necessary, and above all the irregular 

 nature of most of tbe crops dealt with. 



(b) Mixed method. — The volumetric method has been 

 generally replaced by a simplified form, known as the 

 mixed method, the essential feature of whicli is the two- 

 fold and simultaneous division of the exploitable age and 

 the area into corresponding portions. In other words, 

 instead of qaleulating the future growth of all the crops up 

 to the time of felling, tjie total area is divided into a 

 number. of equiproductive blocks, and the exploitable age 

 into a similar number of periods during which each block 

 is in its turn to be regenerated. The yield of that block 

 which is about to be taken in hand for regeneration is 

 then calculated. 



Thus, in the example already taken, instead of calculating the future growth of 

 the crops in all the blocks, and then making transfers from one hlock to another eo 

 as to secure an equal yield throughout, the forest area is partitioned off into four 

 blockg, each about 400 acres in extent or each of eqaiproductiTe resources. 



Thus, hlock I would contain the mature orops, 

 II „ „ large pole crops. 



III ,1 „ younger pole crops. 



IV „ „ young growth. 



; In this partition the size of each block, where the elements of production were not 

 nniforin, would be enlarged or reduced, as the case might be, so that all might even- 

 tnaliy yield about the same quantity of material. The yield of the first block only 

 would then be calculated, Tiiis would be done, as in the previous example, by adding 

 ta the material in the ground estimated growth during half the length of the period 

 — in this case close on 15 years— and by dividing the total so obtained by 30, ih.e 

 number of years in the period. The future growth is obviously taken, as tbe 

 average giowth of the whole for half the period only ; hecause some of the crops 

 would be exploited at the beginning and some at the end of the period. 



Or, when an equal annual volume yield is not essential, the possibility may in 

 some cases be expressed in number of trees by dividing the number of trees in the 

 periodic block to be first regenerated by the number of years in the period. 



The trees in the block under regeneration would, as 

 already stated, be generally removed gradually in several 

 successive fellings. The first, the preparatory or seed 

 felling, would be made with the object of opening out the 

 canopy so as to obtain young seedlings sufficiently lighted 

 for proper growth. The extent to which tliis felling should 

 interrupt the cover would depend on the species constituting 



