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bincd with carbonic acid it loses all these properties, 

 its solubility and its taste : it regains its power of ef- 

 fervescing, and becomes the same chemical substance 

 as chalk or limestone. 



Very few limestones or chalks consist entirely of 

 lime and carbonic acid. The statuary marbles, or 

 certain of the rhomboidal spars, are almost the only 

 pure species ; and the different properties of limestone 

 both as manures and cements, depend upon the nature 

 of the ingredients mixed in the limestone ; for the 

 true calcareous element, the carbonate of lime, is uni- 

 formly the same in nature, properties and effects, and 

 consist of one proportion of carbonic acid 41.4, and 

 one of lime 55. 



When a limestone does not copiously effervesce 

 in acids, and is sufficiently hard to scratch glass, it 

 contains silicious and probably aluminous earth. 

 When it is deep brown or red, or strongly coloured 

 of any of the shades of brown or yellow, it contains 

 oxide of iron. When it is not sufficiently hard to 

 scratch glass, but effervesces slowly, and makes the 

 acid in which it effervesces milky, it contains mag- 

 nesia. And when it is black and emits a foetid smell 

 if rubbed, it contains coally or bituminous matter. 



The analysis of limestones is not a difficult mat- 

 ter ; and the proportions of their constituent parts 

 may be easily ascertained, by the processes described 

 in the Lecture on the Analysis of Soils ; and usually 

 with sufficient accuracy for all the purposes of the 

 farmer, by the fifth process. 



Before any opinion can be formed of the man- 

 ner in which the different ingredients in limestones 



