CHAPTER X. 

 SIZE OF LATERAL DRAINS. 



The size of tile that are to be used on a drainage 

 system should be determined only after all of the data 

 and knowledge to be obtained regarding the land is at 

 hand and all of the grades have been figured out. The 

 following hints as to the manner of taking up this divi- 

 sion of the work may be observed with profit. 



If there are both mains and sub-mains, find how 

 much land is to drain through the outlet of the main, 

 and also how great an area will be drained by each 

 one of the sub-mains. Determine the size of each out- 

 let by the formula, observing carefully the manner of 

 using it. Diminish the size of these drains up-stream 

 according to the area to be drained to that point, taking 

 into account also the grades of the several parts. If 

 the grade is h"ght and uniform the large sizes should be 

 continued well up towards the source of the drain. 

 Each water-shed should be considered carefully by itself 

 and the several basins be connected with each other by 

 the main drain so that the whole will balance and work 

 as one drain. 



Size of Tile for Laterals.— No attempt should be 

 made to make the capacity of intercepting drains equal 

 the combined capacity of the laterals where a system 

 of thorough drainage is employed^ The size of laterals 



