12 A TREATISE ON THE CONNECTION OF 



There are different kinds of such simple, or, as they are 

 frequently called, primary earths ; those which generally 

 occur, and principally regard the object of this Treatise, 

 are, calcareous, or chalky ; argillaceous, or clayey ; sili- 

 ceous, or sandy; and magnesian. It is also necessary 

 to mention, that the earth of iron is likewise contained 

 in most soils, in great abundance ; existing therein, in 

 various states. 



CALCAREOUS MATTER 



CONSTITUTES not only the surface, or soil, but like- 

 wise the under stratum-of many countries, to a very great 

 depth. Under this general name of calcareous matter 

 is included chalk, marble, limestone, coral, shells, &:c. 

 The three first mentioned are frequently mixed with 

 iron, and with different proportions of the simple earths ; 

 but are considered as calcareous, when the proportion of 

 that earth predominates. It is capable of absorbing, and 



of 



