vi.] ACTION OF BURNT LIME. 53 



lime from its original rocky condition into a fine 

 powder. By this reunion ot the carbonic acid with 

 the lime it has now lost its caustic character, it has 

 ceased to be a caustic lime, it has again become 

 carbonate of lime. You will find that if you clearly 

 understand these simple changes in the character of 

 lime, that you will easily distinguish the special ad- 

 vantages which are to be gained by the use of burnt 

 or caustic lime upon the land. 



99. The organic matter in a soil is rapidly 

 acted upon by burnt lime. We have already 

 noticed that the slaked lime quickly draws the car- 

 bonic acid of the atmosphere into combination with 

 itself, and the same action takes place in the soil ; for 

 when the organic matter undergoes decomposition, 

 carbonic acid, or some form of organic acid, is pro- 

 duced and is immediately seized by the lime. This 

 action favours the more perfect decomposition of that 

 organic matter which remains, and as rapidly as the 

 presence of air or moisture permit, fresh food is 

 provided for the lime to lay hold of. The harsh and 

 hungry character of the lime which we called its caustic 

 character soon becomes satisfied by the carbonic acid 

 or other organic acid, and it forms a mild and gentle 

 ingredient of the soil, in the form of a carbonate or 

 other salt of lime. 



100. In some soils we find a large quantity of these 

 organic acids, existing in them to the great injury of 

 the land, and these soils are well known as being 

 " sour." A farmer who has no knowledge of 

 chemistry will tell, quite as accurately as a chemist, 

 when a land is sour, for he judges by the character of 

 the herbage growing on the surface. This herbage 

 is always harsh, and of little value as food. When 

 the mower cuts it with his scythe, he soon finds the 

 cutting hard and difficult, for his scythe quickly loses 

 its sharp edge, and he tells his master that the land is 

 sour and wants lime. The beneficial action of lime 



