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| Keywords: The Quarterly journal of the Geological Society of London (12684395925).jpg 416 PROCEEDINGS OF THE GEOLOGICAL SOCIETY JunC 16 <br> tabular mass above whilst the larger vein terminates abruptly in a <br> rounded knoll <br> Fig 2 � Trap-veins in the Cliffs near Losset <br> a Sandstone and limestone <br> b b Trap-veins <br> Further north similar veins traverse the massive or bedded trap <br> and often project from its surface like rude walls They are well <br> exhibited on many parts of the terrace or raised beach having appa- <br> rently resisted the denuding influence of the sea better than the hori- <br> zontal mass They are also I think often of a harder and more <br> crystalline structure than the latter from which they must differ in <br> point of age <br> One of the most interesting exhibitions of the trap-rocks occurs on <br> the east coast near the ruins of Kilhousland church to the north of <br> Campbeltown harbour In this place a vein of dark ferruginous <br> greenstone divided at right angles to the sides into nearly horizontal <br> columns intersects a mass of light-grey trap which forms the shore <br> for a considerable distance In some places the latter becomes highly <br> concretionary and is divided into vertical columns which cover the <br> shore like a miniature Giant's Causeway These columns are sepa- <br> rated from each other by veins of calc-spar haematite and green <br> earthy carbonate of copper and the whole rock is in some places im- <br> pregnated with the latter mineral The haematite is either compact <br> and siliceous with portions of red hornstone or it is more granular <br> with veins and nodules of calc-spar and grains of green earth or con- <br> tains druses of calc-spar lined with crystals of quartz The haematite <br> veins are sometimes 3 or 4 inches wide but generally much less <br> Occasionally the included column has been entirely removed when <br> the intercolumnar veins remain like empty honey-combs <br> The structure of this singular columnar mass might give rise to <br> many speculations The usual theory of the formation of basaltic <br> columns is that they have been formed by the contraction of the mass <br> in cooling and their position always at right angles to the walls or <br> cooling surface so far confirms this theory In general the prisms <br> fit each other very closely with no wider spaces than the contraction <br> of the mass might be supposed capable of producing Here however <br> we find columns of about a foot in diameter separated by intervals of 35461492 109911 51125 Page 416 Text v 8 http //www biodiversitylibrary org/page/35461492 1852 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 8 1852 Geology Periodicals Smithsonian Libraries bhl page 35461492 dc identifier http //biodiversitylibrary org/page/35461492 smithsonian libraries Information field Flickr posted date ISOdate 2014-02-21 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/12684395925 2015-08-26 20 51 42 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1852 Photos uploaded from Flickr by Fæ using a script | ||||
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