12 A TREATISE ON THE CONNECTION OF 



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

 frequently called, primary earths; those which generally 

 occur, and principally regard the objedt of this Treatise, 

 are, calcareous, or chalky ; argiilaceous, 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, Szc. 

 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 



