94 
SECOND BOOK. 
quantity of water that has been poured into it by 
rain or springs. 
5 . Although water is necessary for plants at all 
times during their growth, it must never be allowed 
to become stagnant round about their roots, if we 
wish them to thrive. When the soil becomes thus 
sodden with water, air cannot enter it, and the land 
then becomes sour and foul, so that most plants 
cannot use the plant-food that is in it. Besides, 
much of the sun’s heat that would otherwise warm 
the land is used in drying up the water. 
6. It is of little use to dig and loosen the soil 
to let in air when the spaces are already choked 
up with water. On the other hand, when water 
drains away freely through the soil, the air rushes 
in to fill up the spaces it leaves. Soils are in their 
best state for growing plants, when air and water 
have about an equal share in filling the spaces in 
them. 
7 . When a soil or subsoil will not let the water 
drain away readily enough, we should make channels 
in the ground to carry it off. Of course we do not 
desire to make the land quite dry, but only to keep 
the water slowly moving through it. 
8. In the hilly parts deep trenches may be dug, 
along which the water that is soaking the lower 
parts of the soil may be led off into some stream. 
Or another plan may be followed, though it is more 
troublesome and expensive. This is to lay pipes 
