LEVELING 
mark, compute the elevation of further points with reference to this 
known elevation. 
The information gained in this survey should be instantly 
recorded in a note-book. From this record a profile should be 
plotted upon suitable paper upon a drawing board. 
DISTANCE IN FEET 
430 50 400 150 200 250 300 350 400 450 500 550 600 
410 — 
=, 
T 
T 
t 
400 
Fic. 20. Prorize or a Roap Securep By LEVELING 
The student should next undertake one or two simple problems 
in cross-section surveying. A tract of land of three to ten acres, 
not too rough and not too level and not too much obstructed with 
trees or buildings, should be chosen. Along one side a base line 
should be laid off, pegs being set at intervals of 50 feet. The profile 
of this line should then be determined with care. Lines perpen- 
dicular to this base should next be laid off from the points marked 
by pegs and running across the area under survey. Then a profile 
survey will be made on each of these perpendicular lines, beginning 
at the peg and taking elevation each 50 feet. The observations 
will all be recorded at once in the field book. 
The elevations thus determined should now be shown in figures 
on a map of squares as in Figure 21. 
The interpolation of contours will be taken up in the next 
lesson. 
49 
