L178 
portion of orchard they cover. Ordinar- 
ily they should cover 10 to 30 per cent 
of the orchard, the larger proportion 
being where the hillsides are steeper or 
where the 1rrigator wants to irrigate hur- 
riedly, and therefore has a large quanti- 
ty of waste water to care for. 
Head Ditch Head Ditch 
fo 
Tilu stration*L 
Low Point 
Illustration No. 1is for a field where the 
general slope is in one direction with low 
point in or near the middle of low side. 
Heavy lines indicate large furrows made 
with two-horse plow on contour levels 
These heavy lines represent practically 
level ditches. 
Illustration No. 2 is where the slope is 
in two directions with low point at one 
corner. Here again heavy lines indicate 
large furrows made with two-horse plow. 
To locate these level contour ditches 
place an instrument at low point, then 
take stakes numbered 1, 2, 3, etc, and 
place them on the two boundary lines at 
elevations six inches, one foot or two feet 
apart, according to the steepness of the 
field. Then turn the instrument up the 
diagonal row and place another line of 
stakes numbered 1, 2, 3, etc., on the same 
levels as those on the boundary. By plac- 
ing these stakes along the fence row or 
under the trees they can be left through- 
out the season. In this way the ditches 
can be cultivated over and remade for 
the next irrigation without the use of 
any instrument or running of levels. 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
Head Ditch 
Cow Point 
Illustration No. 3 shows a head ditch 
running on a ridge diagonally through 
the tract, feeding irrigation rows on 
either side on different slopes. You will 
note there are two low points on this 
tract, requiring that there be two sets of 
contour ditches. The level, however, is 
set as in Illustrations Nos. 1 and 2, at 
the lowest point, and the contour levels 
ascertained in the same manner. 
Illustration No. 4 shows two sorts of 
home-made levels. Hither of these will be 
sufficiently accurate for running these 
contour lines. Of course, a surveyor’s 
‘Tilustration “2 1° 
