Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/508

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Mr. Conybeare on the Strata near

they are, will perhaps convey a clearer notion of the singular configuration of these rocks than could be done by words alone. With the exception of one, which gives a faithful resemblance of some remarkable curvatures in the grauwacke of Hartland Point, the whole of the subjects are selected from those which occurred within the first four miles of our walk from Clovelly westward.

Although these singular contortions are not entirely confined to the dunstone and shillat of Devonshire, they yet occur much more constantly in that rock than in the metalliferous schist of Cornwall. In travelling westward we appeared to lose them gradually. At Bosscastle where the rock evidently approaches nearer to the character of killas, (as it is termed by the miner) they still appear pretty frequently: at St. Agnes they are much rarer and less capricious.

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It is possible that more accurate and minute researches may carry the subdivision of the stratified rocks of this country much further than the present state of our knowledge appears to authorize; but I cannot think that, even with the limited information which we already possess on this subject, it would be assuming too much to establish a line of separation between the rock, which under the provincial names, already mentioned, of dunstone and shillat covers so large a portion of the North of Devon, and that metalliferous slate which lying immediately upon the granite of Dartmoor and Cornwall forms the most considerable portion of the mining tract in both counties.[1]

The former of these, besides the peculiarities already noticed, is

  1. I would wish to be understood as speaking exclusively of the metalliferous slate. That which alternates with limestone at Vevyan, at Padstow, (where it is accompanied by greenstone) and some other spots in Cornwall, will probably he regarded as belonging to a distinct formation.