234 THE NORMAL YIELD. 



Example : — 



Area of forest . = 1 ,000 acres 

 Flotation . . = 100 years 



Annual cutting area = ' = 10 acres, 



if the area is at once re-stocked. 



The annual yield of final returns, according to the table at 

 page 120, amounts to 6,410 + 397 per acre = 6,807 cubic feet ; 

 for ten acres = 6,807 X 10 = 68,070 solid cubic feet. (Final 

 yield during every period of 20 years = 68,070 X 20 = 1,361,400 

 cubic feet.) 



(2.) Intermediate Yields. — These consist of all the thinnings 

 which are made. Taking the same table, the following thin- 

 nings would be made in each year : — 



In the coupe 30 years old = 10 acres, each giving 57c' = 570 



(3.) Total Xormal Annual Yield = 68,070+29,740=97,810 

 cubic feet. The total normal annual yield must be equal to the 

 total annual increment. To cut less than that amount, leads 

 to a higher rotation, and rice rersd. 



h. iS/ie/fer-u-ood Compartment System. 



The calculation of the yield is the same as under the system 

 of clear cutting, as long as the rotation r is maintained. If 



regeneration is commenced later than in the year r — -, the 



rotation is increased, and the calculation must be made 

 accordingly. Supposing the lirst cutting is made in the year 



