68 BENEFICIAL EFFECTS OF DRAINING. 



SECTION III. ON THE CHANGES WHICH RESULT FROM 

 DRAINING. 



When the drain is made and covered (for I always 

 mean here covered drains), the water which falls upon 

 the ground does not remain to stagnate, and does not 

 run away over the surface washing off the besi; of the 

 soil, but sinks gradually down, yielding to the roots of 

 plants any fertilizing matter which it may contain, 

 and often washing out some hurtful substances; as it 

 descends, air and consequently warmth follow it. 

 Under these new influences the proper decompositions 

 and preparation of compounds fit for the sustenance of 

 plants go on, the soil is warm and sufficiently dry, and 

 plants flourish which formerly never would grow on it 

 in perfection if at all. It is a curious fact, too, that 

 such soils resist drought better than ever before. The 

 reason is, that the plants are able to send their roots 

 much farther down in search of food, without ever 

 finding anything hurtful. Every part being penetrated 

 with air, and consequently drier and lighter, these 

 soils do not bake in summer, but remain mellow and 

 porous. Such effects can not, in their full extent, be 

 looked for in a stiff clay during the first season; the 

 change must be gradual, but it is sure. 



SECTION IV. ON THE CONSTRUCTION OF DRAINS, AND THE 

 MATERIALS USED. 



These being the benefits that are to be expected from 

 the introduction of drains into swampy arid wet land 

 of every description, it is obviously important to know 

 how they should be made. With the exception perhaps 

 of large main channels, to which all others converge, 

 or for carrying off small rivulets, the drains should be 

 covered. Open drains occupy much of the land by thei r 



