194 CULTIVATION. 



the soil l)y freezing, as it always does, from the up" 

 right position taken b)^ the particles of ice. 



12. We are enabled to xoork sooner after rams, 

 because the Avater descends, and is immediately re- 

 moved, instead of lying to be taken ofi'by the slow pro- 

 cess of evaporation, and sinking through a heavy soil. 



13. The effects of cold weather are kejyt off longer 

 in the fall, by the removal of the excess of water 

 which would produce an unfertile condition on the 

 first appearance of cold weather. 



The drains also, from causes already named (3), 

 keep the soil warmer than before being drained, thus 

 actually lengthening the season, by making the soil 

 warm enough for vegetable growth earlier in spring, 

 and later in autumn. 



14. Lands are prevented from hecoming sour hy 

 tlie formation of acetic acid, etc., because these acids 

 are produced in the soil only when organic matter 

 decomposes in contact with an excessive quantity of 

 water. If the water is removed, the decomposition 

 of the organic matter assumes a healthy form, while 

 the acids already produced are neutralized by atmos- 

 pheric influences, and the soil is. restored to a condi- 

 tion in which it is fitted for the growth of the more 

 valuable plants. 



15. The decay of roots, etc., is allowed to ])roeecd, 

 Ijecause the preservative influence of too much water 

 is removed, AVood, leaves, or other vegetable matter 

 kept continually mider water, will last fur ages ; 

 while, if exposed to the action of the weatlier, as in 

 under-drained soils, they soon decay. 



