of Growing Timber Trees. 331 



In Table X. of the increase of a bole of 24 feet in height, 

 of a tree growing at the above-mentioned rate, it will be 

 observed, that the contents at 24 years of age arc the same, 

 and at 64 years nearly the same as in the above Table, but 

 the contents of the bole at all the intermediate periods ex- 

 ceed the above. And a 40 feet bole exceeds the above con- 

 tents from 44 years to 100, as may be seen in TaDie XIL 

 For these reasons chiefly I did not think it necessary to take 

 into consideration the decrease in height that takes place irt 

 trees at different ages, according to the kind of tree and 

 quality of the soil. 



The increase per cent, per annum is the same as the above 

 in all trees at the same age, whether they have grown faster 

 or slower, provided their increase in height and thickness 

 annually has not varied on an average. The progress of 

 trees is sometimes greatly retarded by insects destroying 

 their leaves, by unfavourable seasons, and by their roots 

 penetrating into noxious strata. But these accidents cannot 

 enter into calculations. 



Calculations, showing every fourth year from 12 to 64, the 

 progressive annual increase in the growth of trees, and 

 the gradual decrease in the rate per cent, per annum that 

 the annual increase bears to the whole tree. 

 The whole height of the trees is taken to the top of the 

 leading shoot, and the girt in the middle ; but no account 

 is taken of the lateral branches. 



If trees increase eighteen inches in height, and two inches 

 in circumference, annually, their increase will be as under- 

 mentioned, viz. 



TABLE II. 



Explanation 



