FOREST INSTRUMENTS. 149 
measured with a steel tape, and the instrument adjusted to that 
distance by the slide and vertical scale. The top and bottom of 
the tree are then sighted and the readings of the marginal scale 
where the plumb line crosses it added to or subtracted from 
each other, according as the eye of the observer is above or 
below the level of the tree. This instrument may also be used 
Figure 4o. Faustman’s mirror hypsometer. (4BCD.) Frame of in- 
strument, (E) mirror in which scale is reflected, (a) eyepiece, ()) cross-wire 
on which object is sighted, (gc) slide and vertical scale for distance of ob- 
server from tree, (f) spring to hold slide in place, (i) marginal scale which 
gives height of tree. 
in taking levels and grades, and may be mounted on a jacob 
staff or tripod, but is more often used in the hand. Another 
instrument, called ‘‘Baummesser” by the Germans, mounted on 
a tripod, is used to take heights, and by means of a stadia 
attachment the diameter at any point on the trunk of the tree 
may also be measured. After some practice with one of them a 
