Size of Tile 449 



so that it may receive the drain from above and be- 

 low. The sediment brought will then be dropped in 

 the still water of the basin, and may be removed from 

 time to time. To bring the silt basin to the top of 

 the ground, it will be best to use one length of the 

 glazed sewer tile, because this will not be injured by 

 freezing. Where the line of tiles is large, and much 

 sediment is likely to be moved, the silt basin should 

 be dug larger and bricked up. Silt basins should be 

 kept covered to avoid accidents, arid especially in win- 

 ter, to prevent injury to the tile by freezing. 



SIZE OF TILE TO USE 



It is not possible to give specific directions for 

 selecting the sizes of tiles which are best, except where 

 all the details regarding the field to be drained are 

 known. It may be said, in. general, that their capacity 

 must be large enough to remove the excess of water 

 of the heaviest rains which fall inside of 24 to 48 

 hours, but how much this excess may be will vary 

 between wide limits. 



If the tile are 3% to 4 feet deep, and the soil has 

 been depleted of its moisture by a heavy crop, the 

 cases are very exceptional when even a rainfall 

 of 2.5 inches in 24 hours would produce much per- 

 colation into the drains. It is the rains in the 

 spring of the year which will most tax the drains, 

 but it should be understood that so long as the 

 water is moving quite rapidly through the soil it is 

 sucking fresh air in after it, and there is little danger 



oo 



