Etna : a history of the mountain and of its eruptions . n in Figs. 1 and2. They appear, however, to be elongated generally inthe direction of the planes of composition of the twin 1 The figures in this plate are magnified 35 diameters. Fig. of 396. The upper half of the drawing is occupied bya crystal of plagioclastic felspar showing twin lamellation andfaint zonal markings, and with numerous irregular dark-browninclosures of glass, probably containing magnetite dust andmatter similar to that of the groundmass of the rock whichconsists of felspar microliths, granules of olivine, an
Etna : a history of the mountain and of its eruptions . n in Figs. 1 and2. They appear, however, to be elongated generally inthe direction of the planes of composition of the twin 1 The figures in this plate are magnified 35 diameters. Fig. of 396. The upper half of the drawing is occupied bya crystal of plagioclastic felspar showing twin lamellation andfaint zonal markings, and with numerous irregular dark-browninclosures of glass, probably containing magnetite dust andmatter similar to that of the groundmass of the rock whichconsists of felspar microliths, granules of olivine, and augitecrystals, grains of magnetite, and apparently a little interstitialglass. A crystal of augite is shown near the bottom of thedrawing. Fig. 2. Lava of 1689. On the right hand side part ofa plagioclase crystal with inclosures similar to that in thepreceding figure. In the centre a small crystal of similar to that of Fig. 1, but showing a somewhatdefinite arrangement of the small felspar crystals, indicative 3 9
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Keywords: ., bookauthor, bookcentury1800, bookdecade1870, booksubjectvolcanoes
