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11. GRANOPHYRE.—This term, according to Geikie, embraces the greater portion of the acid volcanic rocks of the Inner Hebrides. They are closely allied to the quartz-porphyries, and vary in texture from a fine felsitic or crystalline-granular quartz-porphyry, in the ground-mass of which porphyritic turbid felspar and quartz may generally be detected, to a granitoid rock of medium grain, in which the component dull felspar and clear quartz can be readily distinguished by the naked eye. Throughout all the varieties of texture there is a strong tendency to the development of minute irregularly-shaped cavities, inside of which quartz or felspar has crystallised out—a feature characteristic of the granites of Arran and of the Mourne Mountains.
12. GRANITE.—A true granite consists of a crystalline-granular rock consisting of quartz, felspar (orthoclase), and mica; the quartz is the paste or ground-mass in which the felspar and mica crystals are enclosed. This is the essential distinction between a granite and a quartz-porphyry or a granophyre. Owing to the presence of highly-heated steam under pressure in the body of the mass when in a molten condition, the quartz has been the last of the minerals to crystallise out, and hence does not itself occur with the crystalline form.
True granite is not a volcanic rock, and its representatives amongst volcanic ejecta are to be found in the granophyres, quartz-porphyries, felsites, trachytes, and rhyolites so abundant in most volcanic countries, and to one or other of these the so-called granites of the Mourne Mountains, of Arran Island, and of Skye are to be referred. Granite is a rock which has been intruded in a molten condition amongst the deep-seated parts of the crust, and has consolidated under great pressure in presence of aqueous vapour and with extreme slowness, resulting in the formation of a rock which is largely crystalline-granular. Its presence at the surface is due to denudation of the masses by which it was originally overspread.
EXPLANATION OF PLATE I.
MAGNIFIED SECTIONS OF VESUVIAN MINERALS.
Fig. 1. Section of leucite crystal from the lava of 1868, with fluid cavities. Mag., 350 diams.
" 2, 3, 4, and 5. Sections of nepheline crystals from the lava of 1767, 1834, and 1854.
" 6. Section of sodalite crystal from the lava of 1794, with belonites and crystals of magnetite enclosed.
" 7, 8, 9. Crystals of leucite with microliths and cavities darkened by magnetite dust; also, containing crystals of magnetite.
" 10. Group of leucite crystals of irregular form from the lava of 1855, congregated around a nucleus of crystals of plagioclase and magnetite.
EXPLANATION OF PLATE II.
MAGNIFIED SECTIONS OF VESUVIAN MINERALS.
Fig. 1. Section of augite crystal from the lava of 1794, with numerous gas cells and delicately banded walls. The interior contains two long prisms, probably of apatite.
" 2. Crystal of augite with banded walls, and indented by leucite crystals, from the lava of 1794. Mag., 40 diams.
" 3, 4, 5. Sections of augite crystals from the lavas of 1794 and 1820.
" 6. Group of augite crystals from the lava of 1835.
" 7. Ditto from the lava of 1822, with encluded mica-flake (a) and portion of the glass paste, or ground-mass, of the rock (b), containing microliths and grains of magnetite.
Fig. 8. Two crystals of olivine from the lava of 1855; they are intersected on one side by the plane of the thin section, and are remarkable for showing lines of gas cells, and bands of growth sometimes cellular. Mag., 40 diams.
" 9. Section of rock-crystal (quartz), with double terminal pyramids, from the lava of 1850.
" 10. Twin crystal of sanidine from the lava of 1858. Mag., 40 diams.
" 11, 12, 13. Sections of plagioclase crystals (probably labradorite) from the lava of 1855. Mag., 100 diams.
" 14. Section of olivine crystal from the lava of 1631—imperfectly formed. Mag., 30 diams.
" 15. Section of mica-flake from the lava of 1822. Mag., 30 diams.
EXPLANATION OF PLATE III.
MAGNIFIED SECTIONS OF VOLCANIC ROCKS.
1. Diorite dyke, traversing Assynt limestone, North Highlands.
2. Basalt from upper beds, near Giant's Causeway, County Antrim.
3. Hornblende-hypersthene-augite Andesite, from Pichupichu, Andes.
4. Augite-Andesite from Pichupichu, Andes.
5. Olivine dolerite, with hornblende and biotite, Madagascar.
6. Leucite basalt, with mellilite, Capo di Bove, Italy.
EXPLANATION OF PLATE IV.
MAGNIFIED SECTIONS OF VOLCANIC ROCKS.
1. Vesuvian lava, glass paste with numerous crystals of leucite; others of augite and nepheline porphyritically developed; also small grains of magnetite.
2. Vesuvian lava, glass paste with numerous crystals of leucite; others of olivine, hornblende, and sanidine, porphyritically developed; small grains of magnetite.
3. Trachyte from Hungary; felsitic paste with crystals of hornblende and sanidine, and a little magnetite.
4. Gabbro, from Carlingford Hill, Ireland, consisting of anorthite, augite, a little olivine, and magnetite.
5. Dolerite, from old volcanic neck, Scalot Hill, near Lame, consisting of labradorite, augite, olivine, and magnetite.
6. Dolerite, Ballintoy, County Antrim, showing ophetic structure, consisting of augite, labradorite, and magnetite.
[1] Mr. S. Allport has discovered this in the rock called the "Wolf Rock" off the coast of Cornwall. The most important work on basalt is that by F. Zirkel, Unters. ueber mikros. Zusammensetzung und Structur der Basaltgesteine. Bonn (1870).
[2] Zirkel, Die mikroskopische Beschaffenheit der Mineralien und Gesteine, p. 153. Leipsig (1873).
[3] Zirkel, Petrog., i. 578; B. von Cotta, p. 178 (Eng. Trans.).
INDEX.
INDEX.
Abyssinian table-lands, 190 et seq.
Albano, Lake, 89
America, volcanic regions of North, 136 et seq.; of Western, 144
Andes, 18, 27, 227, 254
Andesite, 263
Antrim, 154 et seq.
Arabia, dormant volcanoes of, 126-135
Arabian desert, 134
Archibald, C. D., 213
Arizona, volcanoes of, 137
Argyll, Duke of, 173
Ascension, 36
Ashangi, volcanic series of, 192
Atmospheric effects of Krakatoa eruption, 213-214
Auckland district, volcanoes of, 147
Auvergne, volcanic regions of, 14, 16, 92 et seq.
Azores, 32
Ball, Sir R. S., 242, 244
Basalt, 260
Blanford, W. T., 188, 189
Bonneville, Lake, 141-142
British Isles, Tertiary volcanic districts of, 154 et seq., 227; pre-Tertiary volcanic districts of, 196 et seq.
Buch, L. von, 6, 11, 24
California, volcanoes of, 140
Callirrhoe, springs of, 133
Canyon, the Grand, 138
Cantal, volcanoes of the, 99-101
Cape Colony, Basalts of, 194
Charleston earthquake, 218, 222, 224
Chambers, G. F., 246
Charnwood Forest, 198
Chimborazo, 18
Clermont, vale of, 96-97
Clinkstone, 263
Cordilleras of Quito, 25
Cotopaxi, 16-18, 24, 26
Crater-cones, Lava, 19
Crateriform cones, 13
Craterless domes, 15
Dana, Prof. J. D., 19, 39, 249
Darwin, 28, 30
Darwin, Prof. G. H., 9, 231
Daubeny, 7, 61, 69
Davison, C., 9, 231
Davy, Sir H., 11
Deccan trap-series, 187 et seq.
Demavend, Mount, 24
Diabase, 262
Diorite, 261
Dolerite, 261
Domite, 263
Dore, volcanoes of Mont, 100-101
Doughty, C. M., 127
Durocher, 232
Dutton, Capt. C. E., 9, 220, 222
Dykes in Ireland, 169-170
Earthquakes, 217 et seq.
Errigal, 10
Etna, 14, 61 et seq., 229
Fingal's Cave, 185
Forbes, D., 27
France, extinct volcanoes of, 92 et seq.
Gabbro, 261
Gardner, J. S., 156
Geikie, Sir A., 8, 29, 143, 156, 160, 169, 172, 176, 177, 196
Giant's Causeway, 165-166
Granite, 264
Granophyre, 264; of Mull, 174
Green, Prof. A. H., 194
Hatch, Dr., 260
Haughton, Prof., 68
Hauran, volcanoes of the, 22, 129
Haute Loire, volcanic districts of, 101-105
Hawaii, volcanoes of, 39, 249, 251
Hecla, 32
Herschel, Sir J., 244
Hibbert, Dr. S., 6, 114, 124
Hochstetter, F. von, 147
Hopkins, 171, 217
Hull, Dr. E. G., 110
Humboldt, A. von, 20, 25
Hutton, James, 5
Iceland, volcanoes of, 30-32
Ireland, volcanic Tertiary rocks of, 154 et seq.
Jaulan, 129
Johnston-Lavis, 52
Jordan valley, 126 et seq., 226
Jorullo, 24
Judd, Prof., 8, 68, 69, 71, 172, 178, 208
Krakatoa, eruption of, 206 et seq.
Kurile Islands, volcanoes of, 28
Laacher See, 121-123
Lampophyre, 262
Lancerote, 34
Lasaulx, Prof. von, 68
Lavas, relative density of, 232-234
Lima in 1746, earthquake of, 222
Lipari Islands, volcanoes of, 69 et seq.
Lisbon, earthquake of, 221
Lister, J. J., 38
Lunar volcanoes, 236 et seq.
Lyell, Sir C., 30, 62, 78, 217
Mackowen, Col., 74
Magdala, volcanic series of, 192-193
Mallet, R., 9, 217
Mauna Loa, 19, 39, 249
Mica-trap, 262
Milne, Prof., 28, 218, 253
Moab, volcanic regions of, 132
Moon, volcanoes of, 236 et seq.
Monte Nuovo, 85
Mull, 172 et seq.
Neapolitan group of volcanoes, 28
New Zealand, volcanoes of, 146
Obsidian, 264
Ocean waves of seismic origin, 208, 220
O'Reilly, Prof., 9, 219
Orizaba, 21
Ovid, 3
Pacific, volcanic islands of, 37
Palestine, dormant volcanoes of, 126-135
Palmieri, Prof., 55
Pantelleria, 74
Phlegraean fields, 85
Phonolite, 263
Pitchstone, 264
Pliny, 2, 4
Porphyrite, 262
Powell, Major, 138
Pre-Tertiary volcanic rocks, 187 et seq.; of British Isles, 196 et seq.
Puy de Dome, 105-110
Pythagoreans on volcanoes, 2-3
Quito, Cordilleras of, 25
Rangitoto, 19, 149
Reyer, Dr. E., 17
Rhine valley, volcanoes of, 113 et seq.
Rhyolite, 263
Riviera in 1887, earthquake of, 219
Rocca Monfina, 80
Roderberg, 119, 120
Rome, 88-89
Rosenbusch, H., 260
Roto Mahana, 151
Ruapahu, 151
Russell, Hon. Rollo, 213
Rutley, F., 260
St. Helena, 37
San Francisco, Mount, 138
Santorin, 76-83
Schehallion, 10
Schumacher, 127
Scotland, volcanic districts of, 172 et seq.
Scrope, Poulett, 5, 73, 93, 98
Scuir of Eigg, 180-184
Seismic phenomena, special, 201 et seq., 217 et seq.
Shasta, Mount, 140
Siebengebirge, 116-120
Skye, 177-179
Sleamish, 168
Smyth, Piazzi, 33
Snake River, volcanoes of, 142
Staffa, 185-186
Strabo on volcanoes, 3
Stromboli, 71-73
Sumatra, volcanic action in, 226
Syenite, 262
Symes, R. G., 167
Syria, earthquakes in, 219
Taupo Lake, 150
Taylor, Mount, 138
Tell el Ahmar, 131
Tell el Akkasheh, 131
Tell el Farras, 131
Tell Abu en Neda, 130
Tell Abu Nedir, 129
Templepatrick, quarry at, 160
Teneriffe, 33
Tertiary period, volcanic activity of, 255
Thucydides, 2
Tonga Islands, volcanoes of, 38
Tongariro, 151
Trachyte, 263
Trass of Bruehl Valley, 123-125
Tristan da Cunha, 37
Tristram, Canon, 127, 131
Utah, volcanoes of, 137
Verbeek, R. D. M., 202
Vesuvius, 4, 14, 41-60, 67, 229
Volcanoes, historic notices of, 1-5; form, structure, and composition of, 10-19; lines and groups of active, 20-29; of mid-ocean, 30-40; extinct or dormant, 84 et seq.; special volcanic and seismic phenomena, 201 et seq.; the ultimate cause of volcanic action, 225 et seq.; whether we are living in an epoch of special volcanic activity, 253-256; brief account of volcanic rocks, 259-265
Vulcanists, 5
Vulcano, 69, 71
Wallace, A. R., 81
Waltershausen, W. S. von, 7, 61
Wellington, Mount, 149
Wharton, Capt., 212
Whymper, E., 18
Yarmuk, valley of the, 129, 131
Yellowstone Park, 145
Zirkel, F., 260
Zoellner, 240
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Transcriber's note:
Changed 'Kilarrea' to 'Kilauea' on page 19: Mauna Loa and Kilarrea.
Changed 'Kilanea' to 'Kilauea' on page 39: Kilanea, 4158 feet.
Made punctuation (semi-colons) consistent in caption to figure 16.
Changed 'Brionde' to 'Brioude' on page 94: till at Brionde it becomes.
Changed 'occuping' to 'occupying' on page 96: occuping a hollow.
Changed 'Rodesberg' to 'Roderberg' on page 118: old extinct volcano of Rodesberg.
Changed 'Wolkenberg' to 'Wolkenburg' on page 118: and that of the Wolkenberg.
Left the reference to Jeremiah, l. 25. in footnote to Part III Chapter I, although Jeremiah, li. 25. seems more appropriate.
Changed 'fumarols' to 'fumaroles' on page 137: fumarols give evidence.
Removed extra comma on page 153: of the present, epoch.
Changed 'columnal' to 'columnar' on page 176: the columnal structure.
Changed 'groves' to 'grooves' on page 183: the groves and scorings.
Changed 'Angust' to 'August' on page 212: the 27th of Angust.
Changed 'mikroskopischen' to 'mikroskopische' on page 260: ueber mikroskopischen Structur.
Changed 'become' to 'becomes' on page 260: the rock become a leucite-basalt.
Left inconsistent spellings of 'Baalbec' and 'Baalbeck'; 'Harrat' and 'Harrat'; 'metres' and 'metres'; 'pitchstone' and 'pitch-stone'; 'prehistoric' and 'pre-historic'; 'Rhone' and 'Rhone'; 'sub-aerial', 'subaerial' and 'subaerial'; 'tableland' and 'table-land'.
Greek words were replaced with their transliterations: 'meson pyr' and 'Peri kosmou'.
The oe-ligature was expanded to the two separate characters: 'Euboea' and 'Boeotia'.
Left the list numbering as is at the beginning of Chapter II of Part IV, even though the list begins at item c, as if it continues the list which began in the previous chapter.
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