THE DEAINAGE OF GRASS LAND. 15 



be held responsible for periodical examiuation 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 horses' feet through a long series of years. A similar condi- 

 tion 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. But in many cases it will be necessary 

 both to break up the subsoil and to put in pipes before effectual 

 drainage can be secured. 



