446 SECONDARY LIMESTONE. 



instances, a much greater variety of hue prevails; 

 different tints of yellow, red, grey, white, and 

 black, being sometimes intermixed in various 

 modes. Such secondary limestones are, like the 

 primary, frequently wrought as marbles for pur- 

 poses of ornament ; as are indeed many of those 

 which, with one colour only, present a texture 

 capable of assuming a proper polish. To notice 

 these in greater detail, is beyond the limits of a 

 work which only professes to treat of mineral dis- 

 tinctions. They are often highly interesting in 

 the arts, and ornamental in cabinets of speci- 

 mens ; but are too easily distinguished, and at 

 the same time far too numerous, to find places, 

 even in the catalogues of varieties ; among which, 

 the distinctions arising from colour have here 

 been systematically neglected, as of a trifling and 

 unimportant nature. 



SYNOPSIS OF SECONDARY LIMESTONE. 



FIRST DIVISION. 



Simple, or nearly so : formed of carbonat of 

 lime with little or no intermixture of other earths. 



