Drainage in New York. 



271 



Kimihcr of acres from ^cliicli '4 incii of zcatcr icill be removed in 

 24 hours bv outlet tile drains of different diameters and different lengths 

 zeith different grades. 



Diameter of Tile in 

 Inches 



Grade in Inches Per ioo Feet 



Length of Drain in Feet 



Elliott says further that, " No attempt should be made to make the 

 capacity of the intercepting drains equal the combined capacity of the 

 laterals where a system of thorough drainage is employed. The size 

 of laterals where the soil is open and permits the use of drains 100 or 

 more feet apart should l)e 4 and 5 inch tile, which in some cases may be 

 diminished to 3 inch at the upper end. For drains at a less distance 

 apart three inch tile may be used for laterals. They are usually required 

 to carry only a small part of their full capacity and relieve the soil 

 of its surplus water. To do this well, however, they should not be 

 quite full at any time unless it be when there is more than ordinary 

 rainfall. They do not work under a pressure head, hence their velocity 

 of. flow is as great when running half full as when running full. Water 

 in a drain attains its greatest velocity when three-fourths full and its 

 greatest rate of discharge when nine-tenths full." 

 /. Distance apart of drains. 



Where the conditions are such as to require a regular system of drains 

 at definite intervals, the interval will still depend on the character of 

 the soil. They will be near together in heavy clay soil and farther apart 

 in sandy soil, In general, however, it is not found desirable even on 



