30 WALL'S MANUAL 



together with fatal malaria, which often renders the 

 surrounding country almost uninhabited. Marshy 

 and swampy lands arc generally not fertile. First 

 Because the stagnant water excludes the air, and 

 causes the vegetable matter to be converted into 

 soluble vegetable acids in such quantities as to be 

 injurious to most plants. Such soils are said to be 

 " sour," and produce nothing but coarse, worthless 

 vegetation. Second The air is necessary to keep 

 up the proper chemical activity in the soil in order 

 to produce the necessary changes in its mineral 

 ingredients. Stagnant water prevents this by exclud 

 ing the air. Third Swampy lands are cold. Water 

 is very slowly heated, compared with soil. Hence 

 lands covered, or even saturated with water, are not 

 readily penetrated by the heat of the sun. Besides 

 this, the constant evaporation which goes on from 

 the surfrce of such lands carries off heat rapidly. 



Draining, by admitting the circulation of the air, 

 promotes the proper kind of chemical changes, in 

 both vegetable and mineral substances, and thus 

 "sweetens" a "sour soil;" and by admitting heat 

 and checking evaporation, brings the soil under the 

 warming influences of the sun. 



The decay of vegetable matter is hastened by 

 draining, and the soil rendered more porous. As 

 soon as drained lands become sufficiently dry for the 

 plow, they should be treated with a free dressing of 

 quick lime, or unleached ashes, to neutralize the excess 

 of vegetable acids, and then broken up to as great a 

 depth as possible to aid the circulation of air. 



There are two modes of draining in common use. 

 The one by surface or open drains; the other by 



