The Soil and its Treatment. 9 



minor or secondary low places, and usually empty into the 

 mains, but sometimes, when the contour of the field is very 

 uneven, it is found more convenient to let them act as smaller 

 mains, with a separate outfall. Small drains should not enter 

 the larger pipes squarely, but at an angle in the direction of 

 the flow of the water, otherwise there is a liability to block 

 with silt or other obstructions. In forming junctions between 

 two pipes a hole should be made through the larger one in 

 a position which will bring the top of each pipe level, the lip of 

 the small one being introduced into the larger one and the 

 place of junction properly covered with pieces of broken tile 

 to keep out soil and silt. 



Plan of Draining of a Field with undulating surface. 

 A Main drain. B, C Sub-mains, used as Secondary Mains. D Stream. 



It is not considered good practice to have field drains longer 

 than 250 yards without a break ; when the distance is greater 

 than this an intercepting main or sub-main drain should be put 

 in n^ar the middle of the field. 



The drains should empty at one or more main outlets. 

 Where a number of small drains enter a ditch separately some 

 of them, sooner or later, get choked by rubbish or lost sight of. 

 It is much easier to attend to the outlet of one main drain 

 than of a number of small ones. 



Drains in clay, if well laid, will work fairly well with a fall of 



