90 



COAL MEASURES. 



3. Ironstone. 



4. Coal. 



5. Beds of limestone, with fresh water-shells. 

 (Total thickness 1000 yards.) 



2. The Carboniferous, or Mountain Limestone. 

 1. Millstone grit, sandstone, shale, and coal. 

 2 Limestone and flagstone, abounding with plants. 

 3. Lower limestone, filled with marine remains. 

 (Total thickness 800 yards.) 



Beneath these, though not considered as forming 

 a part of the carboniferous system, is the old red 

 sandstone, consisting of, 



1. Conglomerates and sihcious sandstones, with- 

 out organic remains. 



2. Flagstones, marls, and concretionary lime- 

 stones ; scales of fishes ; organic remains rare. 



(Total thickness 3500 yards.) 



2. Section of the South Gloucestershire Coal-basin. 

 (Beginning at the top.) 



1. Oxford clay. 



2. Great oolite. 



3. Inferior oolite. 



4. Lias. 



5. New red sandstone. 



6. Coal, alternating with shale and grit. 



7. Millstone grit. 



8. Mountain limestone. 



3. Section of the Coal-field of Derbyshire, 

 (Beginning at the surface.) 



1. Beds of clay (containing fresh-water mussel 

 shells). 



2. Shale, argillaceous slate of a soft texture. 



3. Layors of ironstones in indurated cls^ 



