1 68 CARBONIFEROUS. 



building- and paving-purposes, as at Bakewell Edge, etc. Gritstone has also been 

 worked at Ravvthay Gill, between Ra venstone Dale and Sedbergh ; at Longridge ; 

 and at Gatherly Moor near Richmond in Yorkshire. 



The thin coals, as Prof. Phillips observes, are not worth the expense of the 

 fruitless trials in search of them, although, locally, some seams attain a thickness 

 of four or five feet. Coal has however been worked near Haltwhistle and Hexham ; 

 also at Barbon and Casterton, near Hawes, Kirkby Stephen, and Garsdale Head. 



The Bishopley Limestone, quarried near Frosterley, Durham, the Prudham 

 stone, near Hexham, and the Gilling stone, quarried near Gilling, Yorkshire, are 

 beds of economic value in the Yoredale Series. 



Encrinital Limestone has been obtained from the Twelve-fathom Limestone at 

 Snays-wold, between Dent and Garsdale, also from the Four-fathom Limestone. 

 Some of the beds have been polished for ornamental purposes. 



Bitumen occurs at Clithero. Beautiful specimens of ' Flos ferri,' coralloidal 

 Aragonite, have been met with in the Dufton Mines in Westmoreland. 



UPPER CA RB ONI PER US. 



MILLSTONE GRIT. 



This formation consists of coarse sandstones, grits, shales, and 

 conglomerate, with occasional thin beds of limestone and seams of 

 coal. It generally crops out along the margin of our coal-fields, 

 and indeed forms the immediate foundation upon which they rest ; 

 and from the circumstance of its being below the Coal-measures, 

 and containing, in the South-west of England and South Wales, no 

 valuable coal-seams, it has in those districts been termed the 

 ' Farewell Rock.' The name Millstone Grit was no doubt given 

 because the formation has yielded stone serviceable for millstones. 

 The maximum thickness of the Millstone Grit is estimated at 

 5000 feet. 



The fossils of the Millstone Grit are few ; IMollusca are confined 

 to a few limited horizons, but Plant-remains are common throughout 

 the series. These include Siigmaria, Calamites, Lcpidodcndron, etc. 



The Mollusca include Productiis scmireticulatns, Streptorhynchus 

 creni stria, Athyris ambigua, Spirifera striata, Bellerophon cos tat us, 

 Aviculopecten papyraccus, as well as species of Modiola, Posidonomya, 

 Ofihoceras, and Goniatites. 



Trilobites, such as Phillipsia, have been found high up in these 

 beds near Kirkby Stephen by I\Ir. J. G. Goodchild. Fish-remains 

 belonging to the genera Acrolcpis and Acanthodes have also been 

 noticed.^ Rain-prints, sun-cracks, and worm-tracks have been 

 noticed in the Haslingden Flags. 



At Alston Moor the Millstone Grit consists of alternations of 

 sandstones, shales with ironstone and coal, attaining a thickness 



^ See West Yorkshire, by J. W. Davis and F. A. Lees, edit. 2, p. 123 ; also 

 The Millstone Grit, by Fort Major T. Austin, 1865. The new species described 

 in the latter work have, however, not been generally accepted. 



