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 

 case. 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 is 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 mov- 

 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 



