SECONDARY LIMESTONE. 449 



c. Containing- clay : grey chalk. 



d. Earthy, incompact : chalk marie. 



This last might equally have been enumerated, 

 only with marie. The white limestone of Greece 

 is said to resemble var. a. ; but the want of ac- 

 quaintance with it prevents me from determin- 

 ing its place. 



All the varieties of this division become occa- 

 sionally impure, so as to pass into those of the 

 next. The colours of these limestones are 

 various, as formerly remarked, but the following 

 are among the most common. White, pale grey, 

 dove colour, dark grey, reds of various hue, 

 greyish brown, red brown, dark brown, black. 

 These tints are, as in the primary limestones, 

 sometimes intermixed in various ways ; and the 

 varieties of colour are increased by the intersec- 

 tion of veins of a pure carbonat of lime, or by 

 the presence of organic remains. Such varieties 

 are sometimes wrought as marbles for ornamental 

 purposes. 



SECOND DIVISION. 



Compound, containing a notable proportion 

 of some other earths or substances. 



G G 



