64 THE ADIRONDACK SPRUCE 
It will be noticed, in the precedjng tables, that the average diam- 
eters and heights have been determined only for trees six, ten, 
twelve, and fourteen inches and over, in each type of forest. In 
computing the number of board feet and standards by the method 
just described it was necessary to know the average heights and 
diameters of alltrees from six to nine inches, ten and eleven, twelve 
and thirteen, and fourteen inches and over in diameter in order to 
get the totals by addition as before. The diameters were computed 
directly from the table giving the average number of trees for each 
inch in diameter, and the heights were determined in the following 
way: Having already the average heights for all trees six, ten, 
twelve, and fourteen inches and over, these values were entered on 
cross-section paper, laying off the diameters on the horizontal and 
the heights on the vertical lines. A curve was drawn through the 
points, and the heights corresponding to the diameters in the 
following table were obtained by interpolation. 
Table 17 gives the average dimensions of all trees 
within certain specified limits of size in diameter, on 
four kinds of land. 
Table 18 gives a complete summary of the Spruce 
over two inches in diameter measured on the 1046 
acres. In this case the acres are grouped with refer- 
ence to the total yield, cutting to ten inches, accord- 
ing as it rounds up to 1000 feet, 2000 feet, 3000 feet, 
etc. In each class the total number of acres in- 
volved is given, and the average number of trees per 
acre. For the sake of accuracy fractions of trees have 
been given. In the case of the large diameters there is 
less than one tree of each diameter per acre, and the 
result is often avery small fraction. The fractions have 
been rounded off. 
