INSTRUMENTS USEFUL TO A WOODSMAN. 143 
the tube. A jam nut for setting the instrument is applied to the 
extreme inner end of the shaft, and when turned inward holds 
the same against turning. The measuring arm and frame are 
rigid with the shait, so that when the same is turned in either 
direction they turn together and to the same extent, the same as 
if of one piece. The case stands at a right angle to the measuring 
arm, so that when the arm is placed at the zero point of the two 
scales the case will be exactly parallel with the longitudinal axis 
of the hand level. | 
A slot formed in the top of the main tube is located in line below 
the exposed middle portion of the spirit tube and in line above 
the mirror, and permits the bubble to be reflected in the mirror, 
which is so narrow and placed so close to the cff side of the main 





Fig. 12.—Combined surveyor’s hand level and clinometer. 
tube that it does not interfere with the line of vision through the 
same and a view of the cross wire. 
The hand level is often of use to lumbermen in laying out roads 
and trails and in locating dams. To use the instrument as a hand 
level it must first be set by swinging the case containing the spirit 
- tube into line with the maintube. The observer then sights at an 
object through the tube, which he brings toa level by the bubble 
reflected in the mirror, and then notes whether or not the object 
is above or below the cross wire. If the object is in direct line 
with the cross wire it is on the same level with his eye; other- 
wise the object is above or below the level of his eye, as the case 
may be. | 

