SECONDARY LIMESTONE. 453 



FOURTH DIVISION. 



Containing fragments of limestone, or of quartz, 

 or of d ifferent compo u nd rocks . Conglomerated . 



A. Containing fragments of previous limestone. 



B. Containing fragments or pebbles of quartz. 



C. Containing chert or agate, in fragments. Oc- 

 curs at Clunie in Perthshire. 



D. Containing fragments of argillaceous schist ; 



probably of shales. 



Some of these are necessarily noticed again, 

 for the convenience of the student, under the 

 head of Conglomerate Rocks. 



There are further, as already noticed, many 

 popular distinctions, often very marked, among 

 the limestones, which do^ not admit of being 

 enumerated in a catalogue of this nature. These 

 sometimes depend on actual variations of charac- 

 ter, on the presence of certain organic remains, 

 or on the less important distinction of colour. 

 Sometimes they are founded on geological posi- 

 tion ; not unfrequeritly they are of a local or 

 geographical nature. 



