454 Irrigation and Drainage 



are also used for this purpose, but a section or two of 

 the cast iron sewer pipe of the size of the main will 

 be found better, because more durable. 



Where the laterals are connected with the mains, 

 an effort should be made to introduce the branch 

 above the axis of the main, and where there is fall 

 enough to permit of doing so the method used exten- 

 sively in Europe 

 - seems to be the 



^^^^^^^^^^^^ best. This con- 

 Hi sists in perforating 

 the top of the main 



Fig. 143. Method of connect- -, , , , 



ing lateral with main drain. &nd the bottom of 



After Jui.Kiihn. the end tile of the 



lateral, placing the 

 two openings together, as represented in Fig. 143, but 

 first closing the ends of the tile with a stone and ball 

 of clay. This arrangement allows the lateral to empty 

 itself completely into the main, and prevents it from 

 becoming clogged with sediment by the setting back 

 of water into it. 



Where connection is made direct with the side of 

 the main, it should be done by approaching at an 

 angle down stream, as shown at C, Fig. 142, rather 

 than as at D. This can be done, even if the lateral 

 is at right angles to the main, by curving the ditch 

 gently for a rod or more as the place of junction is 

 approached. With this mode of joining, the least 

 interference is brought about when the two currents 

 unite and there is the least tendency to clog. 



