34 
BULLETIN 512, U. S. DEPARTMENT OF AGRICULTURE. 
a hoe who digs a hole at each position of the rod to serve as guides 
to the plowman who follows immediately and lays out the first 
furrow. This is the cheapest and most satisfactory method of laying 
out level terraces. 
Several terraces may be laid out from one position of the instru- 
ment, depending upon the vertical interval and length of the rod. 
If the entire length of the terrace can not be seen from one position 
of the level, the rodman should retain the rod at the last point visible, 
the instrument should be moved to a new position, and a reading of 
the rod taken. This reading should be used in locating points on the 
terrace line from the new position of the instrument. 
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Fic. 15.—System of level-ridge terraces on a field having irregular slopes. 
The graded terrace is more difficult to lay out than is the level 
terrace, because the rod readings never are the same for any two 
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points on the terrace line. 
The first point on the terrace line is 
found in a manner similar to: that described for the level terrace. 
Assuming that the terrace drains to one outlet, then a fall will occur 
from the middle of the terrace line toward the outlet and a rise in the 
other direction. If, for instance, a grade of 0.4 foot per hundred 
feet be used, and if guide stakes are to be set 50 feet apart where the 
alignment is fairly straight and 25 feet apart on bends, then for each 
25 feet in distance toward the outlet a fall of 0.1 foot would be 
required, and, therefore, for each 25 feet in the direction of the 
outlet the rod reading should be increased 0.1 foot. The distance 
should be measured with a tape. If a variable grade is used the rod 
readings should be computed accordingly. 
