YIELD TABLES 77 
gradations, but represent the exact results from the 
1046 acres. 
The method used in determining the number of years which 
must elapse before the same yield can be obtained as at the first 
cut, and the amount of the cut in board feet per acre after ten, 
twenty, and thirty years was as follows: The table on page 45 
gives the average rate of growth in thickness of trees of different 
diameters on cut-over land, and the tables on pages 66 and 67 give 
the average number of trees per acre of each diameter. Knowing 
the average number of trees of each diameter for the different class_ 
es of Spruce land, on acres scaling from 1000 to 12,000 board feet, 
and the rate of growth of trees of all diameters from five to four- 
teen inches, it is possible to predict the number of trees of 
merchantable size per acre, with their exact diameters, after any 
given number of years, and from these, by the use of the Volume 
Tables, the number of board feet per acre, cutting down to ten, 
twelve, or fourteen inches. Similarly, it was possible to predict 
the number of years which must elapse after the first cut 
(whether the limit was ten, twelve, or fourteen inches) before the 
land will produce again the same amount at the same limit. 
It will be noticed that no allowance has been made 
for the death of trees spared by the first cut. All dead 
trees two inches in diameter and over were callipered 
on 563 acres, and were found to average a fraction 
over three trees per acre. Of these about one tree per 
acre was between six and ten inches in diameter. The 
number of trees over five inches which will die in the 
next twenty-five to thirty years under the new condi- 
tions is believed to be so small that it may be neglected 
altogether. 
