10 



Place the triangle to the eye so as to sight along the longer side, 

 while holding the shorter sides (with the aid of a plumb line) so that 

 the one is strictly vertical, the other horizontal; then shift your posi- 

 tion forward or backward until you can just sight the top of the 

 tree; measure your distance from the tree and add the height of your 

 eye above the ground; the sum gives the height of the tree. After 

 some practice with either of these two methods on trees standing in the 

 open, one may become sufiQcieutly expert in estimating the heights of 

 trees to meet most requirements. 



The most convenient instrument which may be recommended for 

 measuring the height of trees is the so-called ''mirror hypsometer" of 

 Faustman. 



Faustman's mirror liypsometer. 



The instrument (fig. 3) consists of the following parts: 



ABCD — Rectangular wooden board (or brass frame), 7.3 inches long and 3.1 

 inches wide. 

 a — Eyepiece made of brass. 

 h — Frame with hair line. 

 'ge — Sliding scale for registering the distance from the observer to the tree. 

 It consists of two parts, the shifting part with the attachment of 

 the plumb line g^, and the graduated part with a spring attach- 

 ment (/) to keep the shifting part in position. 

 CD/i — Height scale from which the height is read off. 



E — Mirror, of similar length with the board and 1 inch wide, in which 

 the height scale is reflected. 



