UNDERDRAIXING AND DEEP TILLAGE. 129 



kindred. They are so few as to be almost exceptional and are worth- 

 less for agricultural purposes, so that, with little liberty of language, 

 plants may be said to breathe, as we do. Hence as this is a part of 

 their life, one of the conditions necessary to their healthy growth if 

 not their existence, those which have a free access of air are the 

 most thrifty and the strongest. 



By access of air, the decomposition of the animal and vegetable 

 matter in the soil is hastened. This, of course, assists vegetation 

 as it furnishes nutriment for the plant on the very spot where it is 

 needed. Thus the fertilitj'' of the soil is greatly increased. With 

 stagnant water in the soil, however, none of these benefits can be 

 be obtained — the soil will remain shallow and coarse, and the roots 

 will not sink deeply into it, as they need extensive feeding ground; 

 and more than this, the manure on the surface will be of compara- 

 tively little advantage to the soil below — since, if it did sink into 

 it, it would not be decomposed. 



Water is a solvent for the impurities of the air. Ammonia, the 

 active principle in nearly all manures, a prominent constituent of 

 all fertilizers, exists in appreciable quantity in the air. This is 

 especially true of the atmosphere after a drought. Water will dis- 

 solve seven hundred times its bulk of this gas, and even at common 

 temperature and under usual pressure, will take up a large amount. 



Kain water containing ammonia falls to the ground, and passing 

 through the soil to the drain, is relieved of its impurity which, as 

 a fertilizer, remains in the soil. The soil has acted like an absorb- 

 ant filter, allowing only the pure water to pass off. Any one who 

 has tasted the water falling from the mouth of a deep underdrain, 

 must have noticed the purity of the water and its agreeable soft- 

 ness. This is wholly due to the absorption of these impurities 

 which are valuable manure. Thus the vapors from bogs and swamps 

 and undrained soil in general, are all retained and used by land 

 which has been properly drained. 



I notice as another benefit that crops grown on drained soil are of 

 improved quality. The roots are larger, fuller, stronger — so that 

 the weight and value of the crop is much incieased. This has just 

 been incidentally alluded to under a preceding head where we spoke 

 of the increased depth of the soil. Draining prevents the freezing 

 out of roots in the winter. That which we call the " heaving" of 



