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| Keywords: The Quarterly journal of the Geological Society of London (14095863303).jpg VOLCANIC GROUP OF ST DAVID'S <br> 305 <br> In the nature then of the rocks which compose the Pre- Cambrian <br> mass which has its centre at St David's we have proof ot its <br> igneous origin and of the gradual lessening of the magnitude and <br> clearness of the crystals as we approach the boundaries The <br> spherulitic and other structures are also only to be met with in <br> truly igneous rocks This being the case and the relations of the <br> several members recalling those so well described by Prof Judd in <br> the Island of Mull We are justified in seeing in this group the <br> natural products of a volcanic area dissected for us by the hand of <br> time <br> But however strong ma - be the argument derived from this <br> particular mass its force is greatly strengthened by the study of <br> two outlying areas the one on the west and the other on the east <br> in both which the association of the rocks and their minute structure <br> suggest and are explicable by an igneous origin alone <br> That on the west is the remoter part of Eamsey Island which <br> from a geological point of view presents truly magnificent features <br> The finest section showing the relations of the rocks is seen on the <br> south side of Perth Hayog as in the accompanying sketch fig 6 <br> Pig 6 ” View in Forth Hayog looking South <br> Towards the west we have massive rocks of felspar-porphyry carved <br> by the sea into overhanging arches through which it roars and <br> foams and contributing the huge blocks and rounded pebbles of <br> beautiful green-spotted rock which strew the shore In a ravine <br> running south this suddenly comes to an end and a straight fissure <br> is filled with a black substance owing its blackness to the presence <br> Q J G S No 158 X 36941098 113697 51125 Page 305 Text 40 http //www biodiversitylibrary org/page/36941098 1884 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 40 1884 Geology Periodicals Smithsonian Libraries bhl page 36941098 dc identifier http //biodiversitylibrary org/page/36941098 smithsonian libraries Information field Flickr posted date ISOdate 2014-04-30 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/14095863303 2015-08-26 05 51 58 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1884 Photos uploaded from Flickr by Fæ using a script | ||||
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