Geology of the South-east of Devonshire. 461 



flanks of Dartmoor does not belong to the question, as it is due to the long subse- 

 quent protrusion of the granite. 



On the other hand, the limestone of the Ashburton band is exceedingly carbo- 

 naceous, containing even seams of anthracite. The sections about Chudleigh are 

 undoubtedly obscure, but I have endeavoured to represent the structure of the 

 country from Oxencombe, beneath Great Haldon, to the disappearance of the lime- 

 stone near Chudleigh Bridge, by figures 8 A. to E, PL XLII. Taking as a guide the 

 apparent dip of the carbonaceous rocks at one place, they would seem to pass be- 

 neath the limestone ; but against this is the well-section already noticed, and the 

 fact, that where the base of the limestone is exposed, as atWaddon Barton (fig. 8 B.), 

 it is seen to have a very different rock subjacent to it, namely, a fine-grained claret- 

 coloured slate, like that which underlies the equivalent calcareous masses of Newton 

 and Barton. The equivocal appearances along the south base of the Haldons (fig. 8 A.) 

 are caused by a downcast fault of unequal amount, which has brought the different 

 members of two distinct series of rocks into juxtaposition ; and the small patches 

 of limestone about Orchard -well, Luton, Colmansford, and Larcombe Bridge, are 

 not included masses, but merely portions of a great unconformable band pro- 

 truding here and there, owing to the inconsiderable thickness of the shales which 

 cover it. 



The mineral contents of the carbonaceous rocks of South Devon are numerous. Tin and copper have 

 been found beneath Ashburton Down, where the Owlecombe mine has been long worked ; tin also 

 occurs at Ilsington, near which is an old stream-work, and at Christow, seven miles north of Bovey. Lead 

 is found in the above-named parishes, and that of Hennock, between Bovey and Christow, contains silver. 

 Some beds rich in iron have been worked at Ilsington, and they also contain numerous small garnets; in 

 the same rock, but in an altered state, contiguous to the granite, are fine crystals of pseudomorphous 

 amethystine, purple and red quartz. The limestone near Oakhampton contains copper in nodules, which 

 are compactly imbedded in the rock, and present a radiating structure like the pyrites of the chalk, but 

 without their metalliferous appearance ; in the kiln the copper becomes a bright green carbonate. 



Referable perhaps to this period, or more properly to the conglomerates of Ry- 

 don and Ugbrooke, is that thick mass of limestone breccia which at Petit Tor 

 (PI. XLII. fig. 1.), east of Babbacombe, is interposed between the solid hmestone 

 and the new red sandstone. It has been produced at the expense of the subjacent 

 limestone, which is much diminished in thickness, and has partaken of a disturb- 

 ance which has affected both it and the underlying slate. It was moreover con- 

 solidated and again fissured before the formation of the new red conglomerate, from 

 which therefore it must be separated. 



The evidence of the age of the carbonaceous rocks deducible from organic remains 

 is as yet very meagre. Pecopteris lonchitica, Neuropteris heterophylla, Sphenopteris 

 latifolia or acutifolia, with a Cyclopteris, are the only plants I have seen from the 

 shales, except the Calamites of Ugbrooke and Orchard- well, which I cannot refer 

 with confidence to any species described by Ad. Brongniart or Prof. Lindley. This 



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