256 IMPROVEMENT OF THE SOIL 



I. Draining. This mode of amendment can be applied 

 only to stiff clays and swamps, or to lands which have a hard 

 and retentive sub-soil, so that the water, in the ordinary 

 course of things, will not pass off, and leave the land com- 

 paratively dry, for a considerable portion of the season. 



The operations of draining are therefore confined to sur- 

 face draining, draining the soil, and draining the sub-soil. 



1. Draining the surface. In stiff clay soils, if the land is 

 level or moderately inclined, the water from rains and snows 

 is liable to remain on the surface, forming pools in every lit- 

 tle hollow. This prevents the seeds, if sown, from sprout- 

 ing, and injures the crop. When this water is evaporated, 

 the' surface becomes hard and impenetrable by air and heat, 



and by the roots of vegetables. 



Fig. 14. 

 This evil is some- au 



timeseffectuallyre- mMT'^^^^^^mZ^^^^ 

 medied by simply 



throwing the land into ridges (Fig. U) by a process called 

 back furrowing, a process which every farmer knows well 

 how to perform. It will be seen by inspection of this figure, 

 that the water as it falls upon the crown of the ridge h h will 

 pass off down both sides in the same way that it does when 

 it falls upon the roof of a house, and either settle into the 

 sub-soil, if porous, or into the furrows a c between the ridges. 



If the soil has an uneven surface and the water accumu- 

 lates in the hollows, an open drain is the only effectual re- 

 medy. 



But in cases where the surface is level and the sub-soil 

 hard and retentive, resort must be had, 



2. To draining the soil This is effected by penetrating the 

 sub-soil so as to form a passage for the water to pass off from 

 the field, or a reservoir into which it may ooze from the sod. 



The drains by which this is effected may be either open 

 or covered. The latter, or underground drains, are the 



