366 
Indian Forest Records. 
[Yol. I. 
If the trees below and up to the exploitable size be enumerated 
in suitable girth or diameter classes, and the number of years repre- 
sented by each girth or diameter class be ascertained, the annual 
possibility for the first period will under the Burma method be — 
_ The number of trees included in the penultimate girth class (less casaalties) 
The number of years in that girth class 
Surplus stock 
^ A suitable number of years' 
As a rule the surplus stock is removed in the number of years 
represented by the felling rotation. It is evident that the full pos- 
sibility so calculated will only be applicable in the case where the 
whole of the forest is worked over annually. If only a portion of 
the forest be worked over annually the number of trees which will 
have attained the exploitable size in any one compartment will de- 
pend (as has already been shown in considering the Oudh Method) on 
the year in which that part of the forest comes to be worked over; 
and in order that the full possibility may be obtained from each 
portion of the forest as it comes to be worked over it is necessary 
that a stock of exploitable trees, varying in number according to the 
year in which the area is felled over, must always exist on the 
ground. 
Thus, 
Let .r = number of trees in the oldest girth class that will survive 
to reach exploitable size. 
Let n = number of years it takes a tree to pass through the penul- 
timate girth class. 
Then the number of trees annually becoming exploitable over the 
whole area will be =- trees. 
n 
If the felling rotation be equal to r years ; then the number of 
trees annually becoming exploitable in each coupe will be — 
X 
II 
=— , or 
r 
X 
n 
n 
If r be taken equal to n, 
