GROWING BY iRRIGATION. 981 
over the field. When it has soaked for an hour or 
day, according to the soil and the season, the gate is 
opened and all the water not absorbed by the soil is 
rapidly run off to the check below which is filled in 
like manner. After this is soaked well the water 
passes in rotation to the next lower check, or if a 
number of them are filled at one time passes again 
into the canal and on down to another field at a lower 
level. 
This is the system of irrigation by contours. It is 
not a good system when the land has a strong slope, 
as it is evident that all the levees would have to be 
very high and very close together, thus the field 
would be much cut up and of irregular shape. But 
where there is slight fall, say of 6” to 100’ and where 
the land is not of a very smooth surface it is a very 
good way. 
Land may be irrigated very rapidly and at slight 
expense and labor when once laid out in contour ter- 
races or checks. One laborer can turn the water, no 
matter how large the volume, into the upper check, 
may watch it until that has soaked long enough, then 
may open the way for the water to flow into the next 
check below. It is the best system when the land is 
infested with ground squirrels or gophers. They 
are all forced to leave their burrows and come out 
where they can be destroyed. 
There are a few well-defined principles that ought 
to be borne in mind in laying out land with these 
contours for flooding. The contours should not be 
too far apart, else the dams or levees will need be 
