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| Keywords: The Quarterly journal of the Geological Society of London (13937115352).jpg given by Zirkel of spherulites thus weather- <br> ing Microscope sections show a kind of granular micrographic <br> growth with a partial attempt at a radial arrangement the concentric <br> hollows apparently developing within the less fibrous zones If an <br> external part of the lava had been broken up in the flow it would <br> probably be vesicular ; and it is conceivable that under the altered <br> conditions vapours which were contained might expand to form <br> the irregular concentric hollows somewhat in the way described by <br> von Eichthofen§ We might suppose however from the partial <br> and discontinuous spherulitic structure which borders the internal <br> cavity and the exterior boundary that the radial growth was pos- <br> sibly connected in its origin with contraction towards a centre and <br> that planes of weak cohesion might have thus arisen as Professor <br> Bonney suggested in explanation of the spherulitic felsite of Arran <br> The quickly-cooled and probably partially-cooled mass broken <br> up and carried along by the renewed flow of the lava would be <br> doubtless subject to more than one series of contractions and the <br> Geology of North Wales p 220 <br> t As in examples described by Professor Bonney Quart Journ Geol Soc <br> 1882 vol xxxviii p 295 ; cf M A de Lapparent Bull de Soc Geol de Fr <br> 1884 3 e ser t xii p 287 on Jersey nodules <br> X U S Explor of the 40th Parallel Micr Petr p 212 <br> § Jahrb der k -k geol Eeichs 1860 p 181 <br> Pitchstones and Felsites of Arran Geol Mag 1877 dec 2 vol iv p 510 <br> In specimens of the spherulitic felsite which Professor Bonney kindly showed <br> to me the exfoliating layers with their white dust had an appearance not <br> unlike in miniature that of the concentric shells described above <br> Q J G S No 178 u 36940048 113696 51125 Page 253 Text 45 http //www biodiversitylibrary org/page/36940048 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 36940048 dc identifier http //biodiversitylibrary org/page/36940048 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 N02/13937115352 2015-08-26 05 52 23 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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