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| Keywords: The Quarterly journal of the Geological Society of London (12734356324).jpg 410 N STORY-MASKELYNE AND AV FLIGHT ON THE CHARACTER <br> small an angle as to give a stauroscopic figure almost identical with <br> that of a uniaxial crystal <br> In parallel light however the cleavage-plane exhibits principal <br> sections parallel and perpendicular to the edge c a; and a slight <br> opening of the cross perpendicularly to that edge can be detected so <br> that the optic axes would lie in the plane of symmetry The crystal <br> is negative It hardly exhibits any dichroism for light traversing <br> the principal cleavage-plane perpendicularly <br> When heated on platinum-foil a little piece expanded to about six <br> times its original thickness ; after it has been reduced to powder it <br> does not expand at all By long boiling in strong hydrochloric acid <br> it gradually expands and loses constitutional water at about 110° C <br> Heated for many hours at 100° C it apparently underwent no con- <br> stitutional change <br> The powder dried for an hour and a half at 100° C lost no weight <br> In one portion the loss of weight at higher temperatures was ascer- <br> tained ; in another the total amount of water present was directly <br> determined The results are as follow ” <br> o <br> o <br> per cent <br> iring half an hour at 125- <br> -130 C <br> 1-309 <br> ž half an hour at 125- <br> -130 <br> 0-205 <br> ž one hour at 130 <br> 0-025 <br> ž half an hour at 150 <br> 0-231 <br> ž half an hour at 150 <br> 0-179 <br> 1-949 <br> Water evolved at a low red heat <br> 9-717 <br> All water which passes off at temperatures about 100° C has been <br> regarded as constitutional water <br> The mineral has the following composition ” <br> Oxygen Ratios <br> Silicic acid 40-833 21-777 10 <br> Alumina 9-801 4-562 1 R fi1 ft ž <br> Iron peroxide 6-844 2-054 J O'Olb 6 <br> Chromium oxide trace <br> Magnesia 31-338 12-535 6 <br> Soda 0-670 <br> Water 9-717 8-636 4 <br> Carbonic acid trace <br> 99-203 <br> The above ratios correspond with the formula <br> R 2 3 Si0 2 +2 3MgO 2Si0 2 2H 2 0 <br> On comparing the atomic ratios obtained from the analysis of this <br> mineral with those given in Prof Cooke's recently published memoir <br> on the Yermiculites as those of Jefferisite andHallitef respectively <br> J P Cooke 'Proc Amer Ac Arts and Sciences ' December 1873 'Phil <br> Mag ' April 1874 <br> t The choice of the name of this mineral is unfortunate as it is already in <br> use as a synonym for the aluminite Websterite of Halle 35766319 110599 51125 Page 409 Text v 30 http //www biodiversitylibrary org/page/35766319 1874 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 30 1874 Geology Periodicals Smithsonian Libraries bhl page 35766319 dc identifier http //biodiversitylibrary org/page/35766319 smithsonian libraries Information field Flickr posted date ISOdate 2014-02-24 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/12734356324 2015-08-26 19 59 08 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1874 Photos uploaded from Flickr by Fæ using a script | ||||
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