Northumberland and Durham. 95 



coarse grained variety of this rock, closely allied to the porphyry, 

 and the perpendicular cliffs of Hellhole on the opposite side of the 

 Cheviot consist also of the same rock. 



The only metallic ores known to exist in this district are, bog 

 iron-ore, which is found in the bottoms of morasses, and red ochre 

 with nodules of hematite from a small vein traversing the rocks 

 above Langley-ford. The shepherds use the latter for marking 

 their sheep. 



Alluvial matter found on the surface of the preceding formations. 



Blocks or detached masses of different rocks are found scattered 

 over the surface of all the preceding formations and imbedded in 

 the soil. 



Masses of blue coralloid limestone, the produce of the lead-mine 

 district, are found at the surface at Cullercoats above the magnesian 

 limestone. Similar blocks are found dispersed over the other for- 

 mations. 



Masses of close-grained sandstone occur every where in like 

 manner. 



Masses of hard black basalt are found every where in abundance. 

 From this stone the ancient inhabitants of Britain formed the heads 

 of their battle-axes, which the people call Celts. They resemble in 

 shape the tomahawks brought from the South Sea islands. Barbed 

 arrow heads, neatly finished, and made of pale-coloured flint, are 

 frequently picked up on the moors, and are called elf-bolts. 



Masses of porphyry, resembling that of Cheviot, and of the Cum- 

 berland mountains, and of green basaltic porphyry are common. 

 The base of the latter is of a greenish black colour, and contain* 



