THE DRAINAGE OF GRASS LAND 15 



instance where the workmanship has been bad, or where no 

 care has afterwards been taken to maintain the efficiency of 

 the pipes. These ought not to be covered in until they 

 have been proved to work satisfactorily, and as di-aining is 

 usually put out to contract, this matter needs close personal 

 attention. 



It is a safe general rule not to make any single drain too 

 long. Plenty of fall should be given, or the pipes may not 

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

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

 small di-ains should not enter the large di*ains at right angles, 

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

 tum, when the occasional flushing after a sharp storm will 

 prevent the pipes from becoming choked. For short distances 

 near hedgerows or trees, the use of socket pipes securely 

 jointed ^\dth cement — not clay — is to be strongly recom- 

 mended. 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 Hghter 

 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. 



Sometimes there is an indurated pan, or hard mass, formed 

 beneath the cultivated surface by the weight of the plough 

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

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



