XOKTHTJirBERLAJsD A>^D BUEHAM. . o 



III. Caebonifeeotjs System, in fotje Formations. 



1. Tuedian. 



2. Mountain Limestone in two groups. 



a. Carbonaceous. 



b. Calcareous. 



3. Millstone Grit. 



4. Coal Measures. 



IV. Permian System. 



Magnesian Limestone Formation, 



MESOZOIC ERA. 



Y. Triassic oe New Eed Sandstone. 



CAINOZOIC ERA. 



VI. Plistocene. 



Boulder Clay, Gravels, Sand. 



VII. Post plistocene. 



Gravels, Peat. 



IGNEOUS ROCKS. 



Felspathic. 



Porphyry, Syenite. 



AuGITIC. 



Basalt, Greenstone. 



I. CAMBRO-SILURIAN. 



Cambro- Silurian strata occupy but a small area in the western 

 part of Northumberland, and do not occur in Durham. They are 

 highly inclined against the porphyry, in the bed of the Coquet 

 a little above Philip, and extend beyond the source of that river 

 into Scotland. In a deep ravine, eastward of Makendon, they 

 are well exposed ; and the Roman camp at Chew Green is formed 

 out of them ; for some of the rampiers are natural walls of Grey- 

 wacke in situ, the rock having been removed on both sides. 



