VOLUME OF STANDING TREE. 133 
hypsometer. A simple geometrical method is illustrated in the 
figure. A measuring rod is set up at a convenient distance from 
the tree AB, the eye of the observer is at S, and the lines of 
sight to the top and bottom of the tree intersect the rod at a 
and b. Then, by measuring the distances from the observer to 
the rod and to the tree the height is given by the formula 
x~ SC 
SD 
Now, considering the tree as a paraboloid, its basal area 
times one-half the height will give approximately the volume. 
A 
Figure 36. Measuring the height of a tree by-a simple geometrical 
methcd. 
For example: A white pine has a diameter at breast height of 
18.7 inches, and the height of the tree is eighty-four feet; what 
is the volume? By reference to the table of areas of circles the 
area corresponding to a diameter of 18.7 inches is found to be 
1.9072 square feet. Multiplying this by one-half the height, the 
approximate volume of the tree is found—1.907242=80.1024 
cubic feet. 
The Volume of a Standing Tree may be Obtained 
by Employing a Form Factor which has been previously 
determined for that particular species by the felling and accu- 
rate measurement of a great many sample trees of approxi- 
