106 NATUKE TEACHING. 



soils contain very small quantities of carbonate 

 of lime and are known as non-calcareous. The 

 majority of the soils of the British West 

 Indies are non-calcareous, but soils containing 

 large amounts of carbonate of lime are found 

 in Barbados, Jamaica, and Antigua. Calcare- 

 ous soils result from the breaking down of 

 rocks composed of corals and shells, which are 

 to be met with in the islands named. 



2. Carbonate of lime may be recognized 

 by the manner in which it effervesces when an 

 acid is poured upon it. This test may be 

 used to distinguished calcareous from non -cal- 

 careous soils, the former effervescing, the latter 

 not. According to the proportion of fine and 

 coarse particles entering into their composi- 

 tion, calcareous soils may be either light or 

 heavy. 



3. Carbonate of lime is an important con- 

 stituent of soils because it takes part in many 

 changes which go on in them as will be under- 

 stood later ; it is necessary for the production 

 of nitrates from nitrogenous manures ; it 

 reacts with most of the substances employed as 

 artificial manures, so that their application uses 

 up a certain quantity of. the carbonate of lime. 

 There is thus a steady, though small, drain on 

 the carbonate of lime present. This requires 



