428 SUPERIOR SANDSTONES. 



trap, pass into a species of jasper, or into chert 

 They are sometimes found penetrated by oxyde 

 of cobalt, by oxydulous iron, and by carbonat of 

 copper, and they frequently contain pyrites. 



THIRD DIVISION. 



Conglomerates. 



A. Sandstone containing fragments of quartz. 



B. Sandstone containing nodules of trap. 



C. Sandstone containing fragments of previous 

 sandstones. 



D. Sandstone containing fragments of schistose 

 clay or shale, or of limestone, or of both. 



E. Sandstone containing flints. English pud- 

 ding stone ; of Hertfordshire. 



This is sometimes of a loose arenaceous tex- 

 ture ; at others, it is indurated to the hardness of 





 quartz. It is a question whether it does not 



rather belong to the alluvial rocks. 



Organic remains, both vegetable and animal, 

 as already noticed, and fragments of charcoal, 

 are not urifrequent in the sandstones classed under 

 this head. 



