92 



II. — In the group of tnediutn-aged crops — when they 

 are between one and two-thirds that size. 



There is usually no need to count the trees which should 

 be placed in the group of young crops. 



If, when the classification is effected, it is found that the 

 total volume of trees in class I is greater by two-thirds than 

 the total volume in class II, it may be assumed that the 

 crops are in the normal proportion.. In this case, it will be 

 understood from what precedes that a sustained yield will 

 be assured if the possibility is calculated from the volume of 

 the full-aged crops divided by one- third the number of years 

 in the exploitable age. Since no allowance is made for the 

 iucrement, it may safely be assumed that the yield so cal- 

 culated need never be reduced in subsequent revisions of 

 the possibility. 



But the normal proportion of 5 to 3, between the vol- 

 umes of full-aged and medium-aged crops, will not often be 

 found to exist in India. There may be — 



(ffl) excess of full-aged crops, or 

 {b) excess of middle-aged crops. 



Where the volume of the old crops is abnormally large 

 the condition of the smallest trees in the full- aged crops 

 should be examined with a view to ascertaining whether it 

 will be practicable to keep these stems standing till the 

 medium-aged crops are exploited. If it appears that this can 

 be done, a portion of the full-aged crops should be placed in 

 the group of medium-aged crops. In other words, it should 

 be sought to make good the deficiency of medium-aged crops 

 by adding a given amount of wood from the full-aged crops. 



Where the volume of medium-aged crops is in excess, it 

 should be ascertained whether the largest trees in the medium- 

 aged crops cannot be exploited during the period assigned 

 for the felling of the full-aged crops, and it should then 

 be sought to supply the deficiency of full-aged crops by 

 transfers. 



When the possibility has been determined, the length of 

 the felling rotation, during which the whole forest will be gone 

 over by the selection fellings, should be fixed. In the pre- 

 sent case it should, liowever, be one-third or a sub-multiple 

 of one-third of the exploitable age. 



