THE IRRIGATION AOL. 323 



The diagram (fig. 2) shows a field that is furrowed for planting 

 and has subditches dug for the distribution of water. The furrows 

 are made at right angles to the fall of the land and the distributing 

 laterals are constructed at right angles to the furrows, or parallel 

 with the natural water flow. 



As the diagram shows, the main ditch feeds the laterals and these 

 feed the furrows. The laterals discharge into the furrows on each 

 side, the water flowing one-half of the distance between laterals in 

 each direction. The furrows in the diagram are between the rows of 

 cane. In the Hawaiian Islands the cane is generally planted and 

 kept in furrows and not ridged up, and the water is applied in those 

 furrows, running in and out around the cane stalks. In other coun- 

 tries visited by the writer, where irrigation is required during a part 

 of the growing season, the cane is more generally upon the ridge and 

 the water is applied between the rows of the cane, as shown by the 

 diagram. The practice is controlled by such factors as the nature of 

 the soil, the rainfall at specific seasons, and the related questions of 

 drainage. 



In the diagram (fig. 2,) the lines indicating the rows of cane are 

 assumed to be 5 feet apart, which is the usual distance. In some 

 situations, owing to local causes, the distance between the cane rows 

 may be as much as 6 feet or as little as 4 feet. The distance between 

 the laterals is assumed to be 30 feet, which means that the water is 

 intended to flow only 15 feet from each side of the laterals that are 

 feeding the furrows. The lines running midway between but parallel 

 with the laterals represent earth dams in the furrows. These limit 

 the length of flow of the water from the laterals on each side. Only 

 lands having a very even surface can be laid out upon the simple plan 

 of the diagram. 



Before speaking in detail of the methods of applying water, one 

 other system will be described. This provides for the direct dis- 

 charge of the water from the main ditch into the furrows. The 

 system (fig. 3) has been observed by the writer, its results considered, 

 and it is mentioned chiefly to show its essential defects. 



In the system illustrated in this diagram (fig. 3,) the water supply 

 is from a main ditch of considerable size (a width of 5 to 8 feet has 

 been observed,) which feeds the water furrows between the rows of 

 cane direct, as illustrated by the arrows in the diagram. The cane 

 rows are drawn straight through the field. The water flows parallel 

 with the rows of cane and not at right angles to them, as shown in 

 diagram (fig. 2.) Consequently the water has to distribute itself by 

 flowing from the main ditch to the opposite end of the field. As 

 already remarked, this system of distribution is exemplified in order 

 to make clear its very palpable drawbacks, which will be briefly 

 explained. 



