102 CULTIVATION. 



6. Draining causes a more even distrihiitlon of 

 nut)'itious matters among those parts of soil trav- 

 ersedhy roots, because it increases the ease with which 

 water travels about, descending by its own weight, 

 moving sideways by a desire to find its level, or car- 

 ried upward by attraction to supply the evaporation 

 at the surface. By this continued motion of the 

 water, soluble matter from one part of the soil may 

 be carried to adjacent parts ; and another constitu- 

 ent from this latter position may be carried back to 

 the former. Thus the food of vegetables is evenly 

 distributed through the soil. As soon as one parti- 

 cle is fully supplied with any element of plant )iii- 

 trition, further amounts brought by water are carried 

 to the next particle that can receive it — and so on, 

 until the supply of soluble material is exhausted. 

 This food is ready for absoi'ption at any point where 

 it is needed, while the more open character of the 

 soil enables roots to occupy larger portions, making a 

 more even drain on the whole, and preventing the 

 midue impoverishment of any part. 



7. Under-drains improve the mechanical texture of 

 the soil ; because, by the decomposition of its parts, 

 as previously described (4 and 5), it is rendered of 

 a cliaracter to be more easily M'orked ; Avliile smooth 

 round particles, which have a tendency to jjack, are 

 roughened hj the oxidation of their surfaces, and 

 move less easily among each other. 



8. By under-draining, (/rasses are j^rcvcnted from 

 running out. The grasses of meadows usually con- 

 sist of tillering plants, which reproduce themselvea 



