318 DETER:\rTX.\TTON AND REra'T,ATTO\ OF THE YTF.LD. 



increment must be removed ; if the real growing stock is 

 smaller than the normal, less than the real increment must be 

 utilised, until the deficiency has been made good." 



In carrying this excellent idea into effect, however, errors 

 were introduced, which are still upheld b}' some foresters of 

 the present day. 



The procedure is described as follows : — 

 (1.) The increment is calculated as the mean annual incre- 

 ment of a series of years. 

 (2.) The normal growing stock is placed equal to the normal 

 final mean annual increment, corresponding to the nor- 

 mal rotation, muhiplied successively by the ages of all 

 age gradations ; the sum of all these products gives the 



value G„ = / X 5, calculated for the middle of the 



growing season. Here / represents the normal annual 

 increment of all age gradations, which is equal to the 

 volume of the oldest age gradation. 



(3.) The real growing stock is obtained by multiplying the 

 real final mean annual increment by the present age of 

 each age gradation. For this purpose it is necessary 

 to determine for each wood the real final age and the 

 volume at that age. 



(4.) The difference between the real and normal growing 

 stock is removed during such period as the owner, or 

 forester, may determine according to the circumstances 

 of each case. 



(5.) The general formula for calculating the yield, if the 

 deficiency or surplus of growing stock is to be removed 

 in the course of a years, runs as follows : — 



. 1 ^r. n IT , I real Gr. Stk.— norm. Gr. Stk. 



Annual \ ield=:real Increment + 



a 



Y=l + ^"" ~ ^\ 

 a 



If Or<, (r,„ then the last position becomes negative. 



