GEOLOGY 



first may be dismissed as a purely theoretical and unnecessary assumption. 

 The second cannot be disproved, but can be equally well accounted for 

 during the period of denudation and rapid accumulation subsequent to 

 the raised beach formation. The felsitic boulders near Stapledon Com- 

 mon south-west of Torrington' occur at intervals in a north and south 

 line, just as the harder portions of a dyke would remain and withstand 

 surface denudation. The large quartz rock blocks near Gawton' and 

 elsewhere are the portions of the local slates most interpenetrated by 

 quartz veins which have survived the denudation of their less durable 

 surroundings. The boulders of siliceous rock near Hestow farm and 

 elsewhere between Chudleigh and Kingsteignton have been ascribed to 

 greywethers from denuded Tertiaries, otherwise it would be difficult to 

 explain their presence. 



Economic. — The county is rich in materials for the manufacture of 

 pottery, bricks and tiles. The Watcombe ware is made from the Lower 

 New Red clays of that locality, and the AUer ware from the clays of the 

 Bovey valley ; these also furnish materials for bricks and tiles. China 

 clay is worked in the decomposed granite of Headon Down, Lee Moor 

 and Cadover Bridge at and near the south-western border of Dartmoor. 

 Bricks are manufactured from alluvial clays and Head, as at Rumleigh 

 and near West Looe ; from the soil of the Keuper marls ; from the 

 Middle New Red marls ; from the clays and brecciated clays of the 

 Lower New Red at Exeter, Tiverton, etc. 



The Cretaceous rocks furnish the best building stone, in the Beer 

 stone, and whetstones on Blackdown. The Lower New Red breccias 

 and breccia conglomerates, near Paignton, Torquay, Exeter and Halber- 

 ton are quarried for building stone and wallstone. 



The Permian trap rocks afford good building material, as may be 

 seen in most of the churches in the districts in which they occur. 



The Middle and Upper Culm rocks furnish grits and sandstones, 

 locally used for building purposes. The seams of anthracite near Bide- 

 ford, Alverdiscot, etc., are used in the manufacture of a pigment called 

 ' Bideford black.' 



The Coddon Hill beds are quarried for gravel and road metal. 



The Westleigh limestones are quarried for lime-burning and build- 

 ing purposes, Interbanded Lower Culm rocks have been used with 

 other materials in the construction of Tiverton church. 



The Devonian limestones furnish ornamental and ordinary building 

 stones, lime, and road metal. The Upper Devonian rocks have been 

 quarried for slates near Buckfastleigh and elsewhere. The Eifelian have 

 been more largely quarried for the same purpose, at Harbertonford for 

 instance. The Lower Devonian grits are locally suitable for building 

 purposes ; the slates of the Meadfoot series are quarried fbr roofing slate 

 in the Kingsbridge district, and often for building stone, where the 



» Rep. Brit. Assoc. 1876 ; Trans, of Sect. p. no ; and Ussher, 'On the Deposits of Petrockstow,' 

 Trans. Devon Assoc. 1879. 



2 Codrington, ^art. Joum. Geol. Soc. 1898, pp. 271-2. 



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