54 AGRICULTURE. [CH. 



in such a case as this, you will readily understand, 

 arises from the lime combining with these organic 

 acids, which make the land sour, and turning them 

 into a condition in which they are, to say the least, 

 harmless; for the acid or sour bodies present have 

 been neutralized. 



TO i. This removal of the sourness of land is some- 

 times described as a sweetening of the herbage. 

 The two terms practically represent the same change, 

 for when by the use of lime this sourness of the land 

 has been corrected, we find a sweeter and better 

 quality of herbage produced, and the stock in the 

 field prefer it. 



102. In such cases as this the burnt lime acts very 

 quickly upon the organic acids in the soil, and in per- 

 forming its work it shows great energy of action. This 

 has led to its being called quick-lime, in distinction 

 from the dead and inactive forms which lime assumes 

 after its work has been performed. You should, how- 

 ever, remember that burnt or calcined lime, caustic 

 lime, and quick-lime, are all different names for the 

 form of lime which is drawn fresh from the lime kiln. 



103. Burnt lime also acts upon the inorganic mat- 

 ter of the soil, and in many cases it liberates potash 

 and soda from the dormant matter of the soil, and 

 renders them available for vegetable growth. 



104. Its most important action on this portion of the 

 soil is probably in the assistance which it renders for 

 the formation of the double silicates of alumina. 

 These we have already noticed (24) as having a very 

 important influence upon the fertility of the land. It 

 has been stated that there are four of these double sili- 

 cates of alumina which have been described as silicates 

 of alumina in which part of the alumina is replaced by 

 soda, lime, potash, or ammonia. You are probably 

 aware that ammonia is more valuable than potash, 

 whilst potash is of more value than lime, and lime is 

 of more value than soda. The silicate of alumina 



