686 



THE WONDERS OF GEOLOGY. 



Lect. VII. 



superincumbent strata of millstone-grit, which now form 

 a broken, and highly inclined wall around it. Such is 

 Crich Hill— a stupendous monument of one of the past 

 revolutions of the globe — with its arches of rifted rock 

 teeming with mineral veins, and resting on a central 

 mound of molten rock, now cooled down into an amorphous 

 mass of compact basalt.* 



A dike of the volcanic rock called green-stone, in some 

 places eighteen yards wide, and which has been traced 

 nearly seventy miles, traverses the Newcastle coal measures 

 on Cockfield-fell. The coal, at the distance of fifty yards 

 from the dike, is altered in its character, and near its con- 

 tact with the erupted mass is reduced to half-burnt cinder, 

 and sooty coaly matter. Wherever trap traverses coal- 

 deposits, more or less change is always observable in the 

 carbonaceous materials. 



18. Faults in the Coal-measures. — In illustration 

 of the displacements called faults, in carboniferous strata, 



Coal 



Lign. 152.— Erupted Trap-rock, in the Dudley Coal-field. 

 (Sir R. I. Murchiaon's Sit. Syst.) 



1. Erupted Trap-rock. 



2. Coal-measures. 



3. Barrow Fault : upcast of 90 yards. 



4. Coal, charred, and altered from contact with the Trap. 

 a, a, Alluvial soil. 



T shall select a remarkable one that occurs in the Dudley 

 Coal-field, near Barrow Hill (Lign. 1.32). The central mass 



* Sec Medals of Creation, p. 951. 



