218 PRACTICAL AGRICULTURE. 



pass upward by capillary attraction ; and it should be 

 remembered that every particle of water which rises 

 towards the surface, comes loaded with salts, which it 

 brings from deep in the earth and deposits within 

 reach of the roots of plants. Water so rising is never 

 pure. If it enters the roots of plants, it carries salts 

 along with it. If it evaporates, it leaves its salts be- 

 hind, having brought them up no doubt in many 

 cases from deeper in the ground than roots penetrate. 



416. Thus we see that water acts not only as the 

 drink of plants which they take in principally by 

 their roots, but also as a carrier of food for them. It 

 washes the air of all those impurities which would 

 render it unfit to breathe. Falling as rain, it brings 

 to the roots of plants, as food, whatever impurities the 

 air contains; and then, after sinking deep in the 

 earth, it is drawn back by capillary attraction, bring- 

 ing with it such salts as it may have found and dis- 

 solved by the way. 



417. The free passage of the air through the soil is 

 almost as important as that of water. These con- 

 siderations are worthy of the attentive study of the 

 practical farmer. They teach him how to prepare his 

 lands for crops. There must be in the soil that which 

 the plant requires ; and not only so, but it must be 

 brought within the reach of the plant. Water and air 

 are the plant's travelling agents. They must have 

 free course ; and to this end, the soil must be deeply 

 mellowed. It would not be extravagant to say, that 

 after having manured your soil the best you can, you 



