144 THE WOODSMAN’S HANDBOOK. 
The lumberman may also use the hand level in finding the 
height of a hill, or the height of any point on the slope of a hill, 
as is necessary in making topographical maps. To find the height 
of a hill, the observer begins at its base, and after leveling the 
instrument, sights in the desired direction, and notes the point 
ahead intersected by the cross wire; he then advances to that point 
and repeats the operation, and so moyes up the hill from point to 
point until the top is reached. As between each observation he 
advances a height equal to the distance from the ground to his 
eye, the height of the hill will be the product of that distance by 
the number of observations taken. 
The instrument may also be used as a clinometer to ascertain 
the slope of a hill. To do this the observer sights the instrument 
at an object on the slope which is the same height above the 
ground as bis eye and located above or below where he stands, 
according as he is sighting up or down the hill. He now uses the 
hand wheel to swing the tubular case until the bubble shows it is 
level. The measuring arm, which swings with the case, is at the 
same time swept over one or the other of the two scales, and 
indicates upon it the slope of the hill in degrees. 
If the observer will provide himself with a table of natural tan- 
gents he may use the instrument for measuring the height of 
trees. He sights the instrument at the top of a tree and turns the 
handwheel until the bubble shows that the case is level, at which 
time the measuring arm, which swings with the case, indicates 
upon the right-hand scale in degrees the angle formed by a line 
running from the observer’s eye to the top of the tree and a hori- 
zontal line extending from his eye to the trunk ofthe tree. He 
then consults his table of natural tangents, which gives him the 
value of the angle secured, expressed as its tangent or percentage, 
the meaning of which is described on page 142. The tangent or 
percentage of this angle multiplied by the horizontal distance from 
the observer to the tree gives the height of the tree above the level 
of the observer’s eye. He then sights to the base of the tree, and 
in the same manner ascertains the angle formed by a horizontal 
line running from him to the tree and a line running from hiseye } 
to the base of the tree. He now consults his table again for the 
value of this angle expressed as its tangent or percentage and — 

