INCREMENT ON FELLED TIMBER 449 



means previously indicated. Thus, leaving out of account 

 the increase in height growth, the increment equals : 



(7-r) 2 x TT x 50 _ (7) 2 x ?r x 50 



144x4 144x4 



1642 1925 



112 144 



= 14-66 - 13-37 



= 1-29 cub. ft. 

 And the percentage equals : 



200 I'29 



~T < 28-03 

 = 9-2 per cent. 



This percentage is slightly too low, as the increase in height 

 growth for I year has been left out of account. 



Similarly, the increment can be expressed as a percentage 

 on the contents of that which is timber only, after such con- 

 tents have been ascertained. 



Thus, if in the above example the length of the tree to 3 

 inches diameter be 36 feet, and the mean diameter of that 

 length be 8 inches. Then the timber contents equals : 



(8) 2 x7r X3 6 

 144x4 



64 X 22 X 36 



144x4x7 



= 1 2-6 cub. ft. 

 And the percentage equals : 



I>2 9 



i 12-6+13-89 

 = 9-74 per cent. 



In many cases a certain degree of accuracy, in obtaining 

 the percentage increment on timber only, can be obtained by 

 applying Schneider's formula, and using a somewhat smaller 

 diameter than the average diameter. 



Similarly also, as already described, the percentage of 

 compound interest for a period of 5 or 10 years, or the 

 increment for a period, may be ascertained, on felled timber, 



2 F 



