374: WHY SHOULD LAND BE DRAINED? 



affecting vegetation, is very great ; but it is not necessary to 

 the strength of the argument that they should be detailed 

 here, and their sufficient discussion would require too much 

 space. 



Moisture. 



By the moisture of the soil we mean a condition resem- 

 bling that of a sponge which has been dipped in water and 

 then lifted out and allowed to drain. While in the water it 

 was saturated that is, all of its pores were filled with 

 water but on being removed the water all runs out from its 

 pores, except the small amount that adheres (by capillary 

 attraction) to its substance. 



In like manner the undrained soil, after a heavy rain, is 

 saturated. All of the spaces between its particles are filled 

 with water. After draining, this water all passes away, 

 except the small amount which adheres to the surfaces of 

 the particles, and that which fills the more minute pores 

 of these particles. There is enough water in the soil in this 

 condition to supply the demands of plants ; but there is not 

 as there was before draining so much as to interfere with 

 their healthy growth. 



Not the least beneficial effect of draining is that which is 

 the result of the admission of air to its lower and cooler 

 parts, causing a deposit of moisture in dry weather, which 

 is sufficient to supply the needs of vegetation, and to 

 greatly mitigate, if it does not even entirely overcome, the 

 effects of drought. 



