1870.] 



of Sewage Irrigation. 



25 



3. Surface Channels. — For the purpose of distributing sewage 

 by means of open carriers, or surface channels, it may, if desirable, 

 be brought to the head of every field in a covered channel, or it 

 may be permitted to flow through open ditches, as may be most 

 convenient. This system, which is the simplest and most effectual, 

 may be carried out in various ways, according to the configuration 

 of the land. By it sewage can be at all times applied to the plant, 

 as it merely runs in a thin film over the surface of the ground at 

 its root ; but in all cases it is necessary that the land be specially 

 prepared for the sewage by careful levelling, and otherwise accord- 

 ing to its natural contour. This may be done in three ways, which 

 are respectively known as the pane and gutter system, the catch- 

 work system, and the bed system. The pane and gutter system is 

 the best, and is admissible in all fields having a gentle rate of 

 inclination. The land under this system is laid out, transversely 

 between the open carriers that distribute the sewage, quite level; 

 the sewage is brought to the head of the field in an open or covered 

 main carrier running transversely across it, or in the direction of 

 its least fall ; the carriers for distributing the sewage branch out 

 from the main carriers and run down the field in the direction of 

 its greatest fall; the sewage is distributed over the intervening 

 space between the distributing carriers by means of stops or sluices 

 (see Fig. 1) being placed in the carriers, which dam back the 



Fig. 1. 



sewage and make it flow right and left over the ground in a 

 uniform stream. 



The sewage passes from the main carriers into the secondary 



Fig. 2. 



Pane and Gutter. 



carriers at a (Fig. 2), which being dammed up at certain points 

 are caused to overflow, the surplus water being carried away by the 



