16G6 



Report of Farmers' Institutes 



extent of the system. It is not now nncommon for tile as large as 

 two feet in diameter to be used. Three-inch tile in lines not more 

 than six luiiidred feet long ai'c usually best for lateral drains. T"p 

 to fifteen hundred feet a four-lncli tile may be used, providing the 

 grade is not less than four inches per hundred feet. It is difficult 

 to make exact statement concerning the proper size of main drains. 

 In general they should be capable of removing one-fourth of an 

 inch of water from the drainage area in twenty-four hours. Treat- 

 ises on drainage cive tables and formulae bv which these relations 

 may be calculated. An increase in the grade increases the rate of 

 flow of water. Doubling the grade increases the carrying capacity 

 of the drain about one-third. The following figures give some idea 

 of the area of laud drained bv some common sizes of tile when laid 

 at different grades : 



number of acres from which 1/4 INCH OF WATER WILL BE RE- 

 MOVED IN 24 HOURS BY OUTLET TILE DRAINS OF DIFFERENT 

 DIAMETERS AND DIFFERENT LENGTHS WITH DIFFERENT GRADES. 



ANGLE OF JUNCTIONS 



Drains should join at an acute rather than a right angle. In 

 other words the union of two lines of tile should have the Y rather 

 than the T form to prevent the accumulation of sediment where the 

 two streams of water come together. If the arrangement of the 

 laterals is at a right angle to the main they may be curved in tlie 

 last rod of their course. The union should be made at the center 



