TEXTBOOK OF LANDSCAPE GARDENING 
at regular intervals and in two directions, one series at right angles 
to the other. In practice the lines are leveled out in one direction 
only. When plotted they are shown by a map cut into squares 
with elevations shown in figures at each intersection, as in Figure 
Zils 
Contour leveling consists in surveying contours upon the land 
and mapping them on paper. (For definition of contour see page 
51.) This is a useful method but somewhat more complicated. 
For lack of space it will not be explained here; but the teacher is 
urged to give the pupil instruction in contour leveling if time and 
equipment will permit, and especially if plane-table practice can 
be introduced. 
Problems 
The student should first become acquainted with the instru- 
ments to be used. To this end he should take up several simple 
problems in differential leveling. He should work in this way until 
he is sure that he can determine the difference of level between two 
points with reasonable speed and accuracy. 
Profile leveling should then be practiced. Take a section of 
road, or path, not less than one-quarter nor more than one-half 
mile in length. Adopt some point as a bench-mark, preferably one 
the elevation of which is already known. Set up the level and 
proceed as in profile leveling. Measure from the point of beginning 
50 feet along the center of the road and determine the elevation 
of this second point B. Measure another 50 feet and find the ele- 
vation of C. Whenever a point is reached where the leveling-rod 
cannot be seen from the station where the instrument is standing, 
or when the elevation is so high or so low that it cannot be read on 
the leveling-rod, it will be necessary to take up a new station with 
the instrument. The last point for which the elevation has been 
determined is then adopted as a turning-point. When the in- 
strument has been reset the first operation will be to level back upon 
this turning-point, and, using this turning-point as a new bench- 
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