DRAINING. 181 



The main drains should be run along the lowest level of the field, pro- 

 vided the outfall will admit of this. If the lowest level should be near 

 to a hedge, the main drain should be kept back from the hedge at least 

 four or five yards, as, if put too close, the roots of the hedge-plants, or any 

 trees which may be in the hedgerow, will gradually grow into and choke 

 the drain-pipes. 



Small drains should be run into the main ones at regular distances, 

 if the nature of the surface will admit of this ; and if not, they must be 

 put where they can be conveniently got, keeping their thorough efficiency 

 in view. 



The depth of the drains, and the distance apart from each other, must 

 be guided by the nature and character of the soil and subsoil, but chiefly 

 as regards the subsoil. No rule can be laid down to suit all cases. It is 

 certainly an error in having the pipes laid too deep in some soils, espe- 

 cially in stiff clay soils ; and errors are more frequently made in having 

 the drains too shallow. There is generally a hard portion or layer of 

 the soil what is termed the " pan " which must be penetrated to in- 

 sure thorough drainage. This pan lies at different depths in different 

 soils and localities, and therefore must be a guide in determining the 

 depth of the drain. In all cases the main drains should be cut from four 

 to six inches deeper than the small ones, and more especially at the 

 lower end, where there is most water. Unless the main drain is a few 

 inches deeper than the minor drains, the accumulated water in the main 

 will prevent a free flow from the small one. Where there is a rapid fall 

 along the line of the main drain, there is not much necessity for its being 

 deeper than the smaller ones. 



I am now draining a large field on this estate where the soil is a clay 

 loam and the subsoil a clay. At a depth of two feet eight inches from 

 the surface there is a stratum of dark - blue shale, very hard. I am 

 draining this field by cutting the main drain three feet four inches deep, 

 and running small drains parallel to each other at a distance of fifteen 

 feet apart, and these are cut three feet deep. At this depth we get 

 through the shale, and I find that the drains are working admirably. A 

 field adjoining the one mentioned, of a similar nature of soil and subsoil, 

 was drained in a like manner two years ago, and the improvement has 

 been very great. 



The distance apart of the drains must be guided by the same circum- 

 stances as the depth. If the soil and subsoil is at all porous, a greater 

 distance may be put between the drains ; but in* stiff and retentive soils 

 it is an error to have them too far apart. I should say that four yards 

 apart may be considered as the least distance between drains in stiff 

 soils, that seven yards should be the greatest distance apart in the same 

 kind of land. 



