10 PERMANENT AND TEMPORARY PASTURES 



work well after they have been laid some time. A good fall 

 renders them to a considerable extent self-cleansing ; and the 

 small drains should not enter the large drains at right angles, 

 but always obhquely, so that the water may retain its momen- 

 tum, when the flushing after a sharp storm will prevent the 

 pipes from becoming choked. For short distances near hedge- 

 rows or trees, the use of socket pipes securely jointed with 

 cement — not clay — is to be strongly recommended. The slight 

 additional expense may save a large subsequent outlay. 



As to the depth at which the pipes should be inserted, 

 and the distance between the rows, no definite rule can be 

 laid down. Experience has proved that in heavy land they 

 must be near together, and not too deep ; but in Kghter 

 land the lines may be comparatively far apart. It is a 

 common practice to cut the trenches three feet deep and 

 to allow a distance of fifteen feet between the rows, but 

 almost every field has some peculiarity of conformation or 

 subsoil which affects the question. After the pipes are 

 covered in, one man should be held responsible for periodical 

 examination of the outlets, to ensure their being kept in 

 working order. 



An indurated pan, or hard mass, may have been formed 

 beneath the cultivated surface by the weight of the plough 

 and the trampling of horses during a long series of years. 

 A similar condition, resulting from natural causes, is found on 

 some heath lands, four or five inches below the surface. These 

 hard subsoils are as impervious to water as beds of cement. 

 Before putting drain-tiles into such land, an experiment 

 should be made to ascertain whether satisfactory drainage 

 cannot be obtained by breaking up the subsoil to a sufficient 

 depth. If the trial prove successful, the expense of putting 

 in tiles may be saved, and the fertility of the land will be 

 increased. In many cases it may be necessary both to break 

 up the subsoil and to lay in pipes before effectual drainage 

 can be secured. 



