GROWING BY IRRIGATION. 281 



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 t)f 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 wliere 

 the land is not of a very smooth surface it is a very 

 go'bd 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 



