INSTRUMENTS USEFUL TO A WOODSMAN. 103 
- The thumb is in such a position as readily to press down the small 
brass knob which releases the circular pendulum on the inside of 
ease. By an easy motion of the elbcw, the small peephole is 
brought close to the eye of the observer. The square window, 
directly opposite the peephole, is pointed toward the object whose 
height is to be determined. The light enters from the large window 
on the face of instrument. 
With the thumb pressing the release, the sight is taken on the 
object and the height is read at the same time; or the thumb may 
be lifted, and the pendulum thus being clamped, the height of the 
tree may be read through the window. 
If the observer stands only 50 feet from the tree the reading must 
be divided by 2. If he stands 200 feet away it must be multiplied 
by 2, and proportionately for other distances. 
The reading gives the height above the level of the eye. | Allow- 
ance must be made if the observer’s eye 1s above or below the stump 
height of the tree. 
The notebook and pencil are held in the right hand while an 
observation is being taken, and the notebook is passed to the left 
hand when the observation is entered. The hypsometer being on 
the back of the fingers allows free play for the thumb, palm, and 
ends of the fingers of the left hand to hold the notebook. In movy- 
ing from station to station the right hand is then free to assist in 
getting through the brush or in crossing logs. : 
The circular pendulum is graduated to tangents. Therefore it 
may be used to determine the per cent of grade of a road or trail. 
For this purpose sights may be taken downhill as well as uphill. 
No conversion of figures is necessary. If the reading is 10 the grade 
is 10 per cent. (See fig. 10.) 
Combined Surveyor’s Hand Level and Clinometer. 
This instrument (shown in fig. 11) has a telescoping surveyors’ 
hand level of ordinary construction, except that its spirit tube is 
located above instead of in its main tube, which, however, contains 
the usual inclined steel mirror and sighting cross wire. 
Combined with the hand level is a clinometer comprising a plate 
screwed to one side of the main tube of the hand level and having 
engraved upon it a curved right-hand scale and a curved left-hand 
