110 NATURE TEACHING 



Chalk in Soils. 



Carbonate of lime, or chalk, is present in some soils 

 in such quantities, that they are distinguished as chalky 

 or calcareous. Other soils contain very small quantities 

 of carbonate of lime, and are known as non- calcareous. 

 A large portion of the soils in Great Britain are non- 

 calcareous, but there are extensive areas where the 

 principal rocks are chalk and limestone, and as these are 

 almost pure carbonate of lime, the soils formed from them 

 are often very rich in this same substance. Examples 

 of calcareous soils occur in Kent, Surrey, Yorkshire, 

 Norfolk, Cambridgeshire, Bedfordshire, the Isle of Wight, 

 in all of which chalky rocks are found. A band of lime- 

 stone extends right across England from Dorsetshire to 

 Yorkshire, and on this calcareous soils are found. 



Calcareous soils are formed by the breaking down of 

 the chalk and limestone rocks of these districts. 



Carbonate of lime may be recognised by the manner 

 in which it effervesces when an acid is poured upon it. 

 This test may be used to distinguish calcareous from 

 non-calcareous soils, the former effervescing, the latter 

 not. According to the proportion of fine and coarse 

 particles entering into their composition, calcareous soils 

 may be either light or heavy. 



Carbonate of lime is an important constituent of soils, 

 because it takes part in many changes which go on in 

 them, as will be understood later. Carbonate of lime 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 



