49 



IV. CALCAREOUS SOILS. 



Any intelligent observer, who attentively examines a 

 geological map of Ireland, will perceive that the limestone 

 formation is not only much more largely developed than 

 any other of the rocks from which our soils are derived, 

 but that it nearly equals all the others collectively. Yet 

 it does not follow, that because limestone forms the plat- 

 form of so extended a surface, all the soils reposing upon 

 it are calcareous. It is well known to agriculturists, that 

 lime, when artificially applied to a soil, has a tendency to 

 sink rapidly to the subsoil. Those soils, therefore, are 

 alone to be termed calcareous, into which the carbonate 

 of lime enters as a necessary constituent. 



The varieties of calcareous soils are 1, marly; 2, 

 gravelly; 3, stony, 



1. Marly. Rich marls frequently occur throughout 

 Ireland, containing from 50 to 91 parts in 100 of carbonate 

 of lime. They are sometimes white and sometimes of 

 a blue colour, and of great value, when properly applied, 

 as a manure ; when this becomes intermixed with the 

 upper stratum of earth, the soil is called marly. The 

 limestone which they contain is so finely comminuted and 

 mixed with other earths, that it keeps the soil open and 

 free, and furnishes an inexhaustible supply for growing 

 crops. 



2. Gravelly. The soil, in many places throughout the 

 limestone formation, is composed of limestone gravel, more 

 or less fine, well suited for the growth of oats and green 

 crops. Sometimes calcareous sand prevails, and shells, in 

 maritime situations. 



3. Stony. On the declivities of mountains limestone, or 

 loose coarse soil, is sometimes found, in which large occa- 

 sional protuberances of the rock occur. To all such lands 

 the term stony is to be applied. 



