114 THE BOOK OF FORESTRY 
Every forester or boy who goes in the woods should 
learn how to estimate the sizes of trees. The diameter 
breast high is easily obtained by measuring the circum- 
ference with a string or tape and dividing this circum- 
ference in inches by three and one-seventh. The diam- 
eter is always measured breast high, 1. e., four and 
one-half feet from the ground. 
Estimating Tree Heights—When it comes to height, 
either total height or merchantable height may be 
meant. The latter is the length of the tree that would 
go into saw logs. In the case of soft woods, like pines, 
spruce, and hemlock, the total height is generally 
obtained, while with hardwoods, like oak, maple, tulip, 
and poplar, the merchantable height is more useful. 
In each case the method of obtaining the height is 
the same. The forester gets the height of a tree by 
using an instrument called a hypsometer. He sets a 
scale to one hundred feet, paces off this distance from 
the tree, takes his readings and gets the height of his 
tree in feet. However, there are several good ways 
of estimating the height of a tree without the use of an 
instrument. A pole say ten feet long can be leaned 
against the tree and the number of pole lengths to the 
top of the tree can be counted. 
One of the simplest methods is to cut a straight 
stick about three feet long. Held in the right fist, the 
grip is shifted until with the arm stretched out hori- 
zontally the tip just touches the eyebrow when the wrist 
is bent. Then when the arm is extended with the stick 
upright, a triangle is formed having two sides equal, 
the eye to the fist and the fist to the tip. Selecting a 
side of the tree to be measured where both top and base 
ean be seen the holder backs off until, with the head 
stationary, the base of the tree can be seen over the 
