32 THE SOIL OF THE FARM. 



due attention to the disposition of the sectional strata of 

 the district, for the porous soil may be surcharged Avith 

 water from a higiier level, and the proposed cure might 

 only prove an aggravation of the existing evil. In tluit 

 case the object may be obtained by cutting a deep ditch 

 or canal through the bank on a level with the bottom of 

 the lake. 



In ordinary practice it is the texture of the soil and 

 subsoil, and the nature or the slope, which determine 

 the proper depth and distance of drains. Deep drains 

 are longer in beginnmg to flow, but, if the soil is porous, 

 they will carry off the surface water, after heavy rains, 

 sooner than shallow drains. They also drain a greater 

 bulk of the soil, and allow the water time to deposit the 

 particles of mould and manure which it carries down from 

 the surface of the ground. 



In an open soil, which the water penetrates freely, the 

 drain will draw from long distances if the depth is great; 

 but in stiff, compact soils, percolation is more difficult, 

 and the drains will draw from a smaller distance than in 

 free and open soils where the water finds a ready escape. 

 Ko amount of 'depth Avill compensate for excessive dis- 

 tance on a compact soil, because the material either re- 

 sists the passage of the water altogether, or the removal 

 is so slow that the drainage is worthless. 



The requirements of vegetation must also be considered 

 in determining the proper depths of drains; and the 

 depths to which the rootlets of the plants penetrate may 

 afford some indication of how far the free sul)jacent water 

 should be permitted below the surface. As its availability 

 for their supply will be regulated by the porosity of the 

 soil, the bottom (5f the drains may be at a less distance 

 from the roots on a heavy soil than on a light one. In 

 dry summers, grass-land, especially, is sometimes liable 

 to injury, owing to the land being dried below the root- 



