CHAPTEE IX. 



PERIOD OF FELLING. 



TREES, like all other organisms, have their periods 

 of growth, maturity and decay, and necessarily 

 there is a period at which, varying in different 

 trees, the annual increment has attained its highest 

 point. Let us say that at sixty years an acre contains 

 2400 cubic feet timber, and increases 600 cubic 

 feet in the next ten years ; and 500 cubic feet in 

 the second ten years, and we say it has passed its 

 highest rate of increase at seventy to eighty years ; 

 but it has not yet passed its highest average. 



2400 

 At 60 years we have -- = 40 cubic feet per annum. 



600 



At 80 > + -43-7 



If it increase 800 cubic feet in the next twenty 

 years, then 



MOO + 600 + 600 + 800 _ 43 ^ ^ per annum 



And we now say it has attained its highest average 

 between eighty and a hundred years, and that that is 



