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Published online by Cambridge University Press: 01 May 2009
The main feature of the geology of Drake's Island is the association of volcanic rocks with marine limestone of Mid-Devonian age. The Geological Survey memoir by Mr. W. A. E. Ussher attributes the discovery of the volcanic rocks to Mr. R. N. Worth. Mr. Ussher leaves their precise nature, “whether lavas or tuffs,” somewhat in doubt, but states that they are “most certainly contemporaneous”. As a matter of fact both lava and tuff occur, and are definitely distinguishable.
page 262 note 1 The Geology of the Country around Plymouth and Liskeard, 1907Google Scholar.
page 263 note 1 “The Dunstones of Plymouth and the Compton-Efford Grit”: Report and Transactions of the Devonshire Association for the Advancement of Science, Literature, and Art, vol. xlviii, p. 217, 1916Google Scholar.
page 264 note 1 Worth, R. H., op. cit., p. 225, pl. iii, fig. 13Google Scholar.
page 265 note 1 Mr. Worth describes and illustrates additional occurrences of chertcarbonate rock from Plymouth; he regards the type as a product of the contact alteration of slate (op. cit., pp. 234–6, pl. iv, figs. 20–2). Professor Jehu, T. J. and DrCampbell, R. have found chert-carbonate rock among the fragments of a volcanic breccia on the border of the Scottish Highlands; “The Highland Border Rocks of the Aberfoyle District,” Trans. Roy. Soc. Edinburgh, vol. lii, p. 183, 1917Google Scholar.