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| Keywords: The Quarterly journal of the Geological Society of London (13937141821).jpg 264 <br> MISS C A RAISIN OS SOME <br> crust ; but this is thin compared with the quartz-tilled interior and <br> may represent the early development rather than the vanishing <br> traces of large spherulites fig 9 Crystals of felspar occur close <br> Fig 9 ” One half of a Siliceous Amygdaloid with a narrow sjfheru- <br> litic border From old lava-flow at south-east of Pen-y-chain <br> Enlarged 8 diameters <br> This specimen is from a rock which contains the amygdaloids of fig 8 <br> to the nodules being actually sometimes in contact with them ; some <br> are kaolinized others exhibit plagioclase twinning but in none is <br> there a replacement by quartz-granules The nodules are elongated <br> and in more than one instance they bend around the angle of a <br> porphyritic crystal at a little distance from it just as would often <br> occur in the formation of a vesicle Thus they seem to be amyg- <br> daloidal and in that case we should be justified in concluding that <br> similar cavities once existed in the neighbouring beds around which <br> a spherulitic growth arose; according to Lagorio it would be especially <br> induced where gases and vapours passed through the rock <br> The above interpretation seems corroborated by some small <br> pyromerides from Jersey in which the interior has all the appearance <br> of similar oval-shaped amygdaloids A slide cut from another rock <br> at Boulay Bay exhibits a contorted fluidal structure with appar- <br> ently rounded quartz-filled vesicles as if the rock was originally <br> glassy and pumiceous Small veinlets of fibrous chalcedony extend <br> between the lines of flow or curve around the vesicles An attempt <br> at spherulitic growth seems to fringe the vesicles the chalcedonic <br> veins and the surfaces of contorted fluidal masses It had been <br> suggested by Professor Bonney from his observations in the field <br> that some pyromerides might possibly be connected in their develop- <br> ment with a differentiation of material in the lava such as gives <br> rise to a fluidal structure <br> We might compare with nodules produced as I have just sug- <br> Min Mittheil Bd viii p 421 Abstract in Min Mag 1887 vol vii <br> p 223 36940057 113696 51125 Page 262 Text 45 http //www biodiversitylibrary org/page/36940057 1889 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 45 1889 Geology Periodicals Smithsonian Libraries bhl page 36940057 dc identifier http //biodiversitylibrary org/page/36940057 smithsonian libraries Information field Flickr posted date ISOdate 2014-04-21 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/13937141821 2015-08-26 05 57 27 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1889 Photos uploaded from Flickr by Fæ using a script | ||||
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