CHAPTER V 



DIFFERENT KINDS OF SOIL 

 {Continued) 



IME STONE is the rock from which lime is 

 obtained. It is composed of carbonic acid 

 and lime. To obtain the latter, the limestone is sub- 

 jected to intense heat in a furnace or lime-kiln. The 

 carbonic acid escapes, is dissipated in the air, and 

 only the lime remains. In arable land limestone is 

 found rather often in smaller or larger pieces, but 

 more frequently as a fine powder which the eye 

 can scarcely distinguish from the other constituents, 

 especially clay. The water of rivers and other 

 streams almost always contains a small proportion 

 of dissolved limestone. Thence comes the thin layer 

 of stone that accumulates little by little on the in- 

 ner surface of bottles, coating the glass. Some wa- 

 ters contain enough of this dissolved limestone to 

 deposit a mineral crust on objects immersed in them, 

 as mosses and aquatic plants, and to obstruct their 

 aqueducts. The clearest water, in which no foreign 

 substance can be seen, absolutely none, nevertheless 

 contains dissolved limestone, just as sweetened water 

 contains invisible sugar. In drinking a glass of 

 water we drink a little stone at the same time. Our 

 body, in order to grow strong and increase in size, 



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