66 



interval of time varying from 10 to 30 years would, 

 therefore, generally be that within which the prescriptions 

 would run. 



Area operated on. — The area to be operated on each year 

 may be determined by dividing the number of acres in the 

 whole forest, less blanks, etc., by the number of years in 

 the felling rotation, and then by apportioning to each block 

 or natural sub- division, according to the fertility of the 

 soil, a certain number of coupes each of that area. 



The following example will explain this process. Suppose a forest of 3,870* 

 acres containing a crop consisting of three types, only one of which is at present 

 productive owing to the others containing no saleable species; also that four blocks, 

 bounded by roads, rivers or other landmarks, have been formed and analysed as 

 follows t — 



We will assume that the felling rotation adopted is 15 years, Rnd that it is, 

 consequently, required to divide the total area into 15 portions of equal forest 

 productivity. This may be done as follows : — 



Total area of forest .... 

 Deduct blanks and unexploitable areas . 



Total exploitable area 



3,000 



3,870 acres. 

 870 „ 



3,000 „ 



The average aftato be operated on annually is ?^=200 acres. In order to lay out 

 these areas each block may be divided into an integral number of coupes containing 

 an area of exploitable forest greater or smalUr than the average according to fert.hty 

 of the soil Thus Paimar, Datwind and Haigla, containing very good fertile soil at 

 ?he base of the hills, might each be divided into coupes containing on au average 

 w than 2(K) acres of sal forest ; whilst Baira, situated iu rocky ground m the hiUs 

 whe2the^aU;;o1 the soil is poor, might he divided into five portions, each 



* It need hardly be explained that small areas of anexploitable forest would be included vrhcre 



ueccfcsary ia a working-circle, 



F 



