322 



THE IRRIGATION AGE. 



tour. The notes of the survey will show the direction in which the 

 cane furrows shall be constructed and also show where the laterals 

 which feed the furrows should be located. On uneven ground the 

 furrows are curved in order that the grade may be kept uniform. 



If a field is practically level and there are vast areas of relatively 

 level land in locations where cane sugar is likely to be grown the 

 furrows are dug straight through the field. The most level field, 

 however, usually has a dominant decline in some direction which is 

 usually determined by the general formation of the lands of the 

 region. The Hawaiian Islands are .of volcanic origin, and hence the 

 general slope of the land is from the craters to the sea. The country 

 is mountainous in the neighborhood of the volcanoes. The slopes 

 become flatter as lower levels are reached, until the decline apparently 

 disappears in the lands bordering on the seacoast. The latter have 



FIG. 2. Irrigation of sugar cane on level land by means of laterals. 



been deposited by streams running from higher lands. In spite of the 

 flat appearance of these lowlands they generally have a decline 

 toward the sea which is not only sufficient to make the distribution of 

 water a simple matter, but also to effect the discharge of underground 

 water. This, however, is not always the case, the writer having 

 several tracts in mind where the ground water can not find a dis- 

 charge owing to its service being but slightly above the level of 

 high tide. 



