ABICH, cited, 122
— researches of, 4
Absorption of gases by liquids and solids, 354, 355
Acid lavas, 48
Æolian Islands. See Lipari Islands
Æolus, origin of myth, 35
Africa, volcanoes of, 227
— South, diamonds of, 147
Agates, formation of, 150
Allport, Mr., cited, 259
Alps, formation of, 292
Altered lavas, names given to, 261
America, volcanoes of, 227
Amygdaloids, formation of, 140, 141
Andesites, 50, 59
Andesite-volcanoes, 126
Andrews, Professor, cited, 321
Anne Boleyn and Etna, 3
Armstrong, Sir W., hydro-electric machine, 29
Arthur's Seat, 275
Artificial stone, 55
Asia, volcanoes of, 227
Asiderites, 316
Asmanite, 314
Astroni, crater-ring of, 170
Atlantic, volcanoes in, 223
Auvergne, breached cones of, 123, fig. 40
— denuded cones in, 124, fig. 42
— incrusting springs of, 184
— puys of, 152, 212
— volcanic cones in, 79

BALL-AND-SOCKET structure in basaltic columns, 107
Barrancos, formation of, 209
Basalt, controversy concerning origin of, 249
Basalts, 49, 50, 59
Basaltic columns of Bohemia, 107
— — of Central Germany, 107
— — of Monte Albano, 107
— — from the Giant's Causeway, 107, fig. 29
Basic lavas, 48
Bath, hot spring of, 219
Ben Nevis, 274
Bohemia, volcanoes of, 126
— lavas of, 103
Boiling. See Ebullition
Bonney, Professor, cited, 69, 109, 259
Boracic acid at volcanic vents, 216
Bourbon, volcano of, 176, figs. 74, 75
Bracciano, crater-lake of, 178, fig. 77
Breached cones, 123, fig. 40
Babbles of steam, escape from lava, 21
Bubbles, spontaneous movement of, in liquid cavities, 62, fig. 8
— — cause of, 65
Buch, Von, researches of, 4
Buda-Pesth, deep well of, 335, 341
Büdos Hegy, Transylvania, 215
Bunsen, cited, 201
Burning, does not take place at volcanoes, 2

CADER IDRIS, 274
'Calderas,' formation of, 180
Caldera of Palma, 209
Cambro-Silurian volcanoes of British Islands, 274
Campi-Phlegræi, map of, fig. 11
— — volcanoes of, 79
— — tuff-cones of, 118
— — fissures in, 197
Carbonic acid in cavities of crystals, 63
Carboniferous volcanoes of British Islands, 275
Carlsbad, Strudel of, 218
— Strudelstein of, 184
Caspian Sea, mud-volcanoes of, 182
Catacecaumene, volcano cones in, 79
Cause of proximity of volcanoes to sea, 239
Central Asia, volcanoes of, 236
— America, mud-volcanoes, 182
— Pacific, volcanoes of, 236
'Challenger,' H.M.S., voyage of, 73
— — soundings of, 359
Chance, Messrs., of Birmingham, 55
Charnwood Forest, ancient volcanic rocks of, 259
Chemical deposits at Vulcano, 44
— — on surfaces of lavas, 110
— elements present in lavas, 46
— theory of volcanoes, 344, 346
Chiaja di Luna, 108
Chimborazo, size of, 44
— 151
Chodi-Berg, Hungary, 161
Citlaltepetl, view of, 169, fig. 69
Coast-lines, proximity of volcanoes to, 228
Cole, Mr. Grenville, 110
Colours of lavas, 49
Columns in lava, 105
— — dimensions of, 105
— radiating in intrusive masses, 136
Columnar structure in lavas, 104
— — origin of, 105
Columnar lava-stream on the Ardèche, 107, fig. 28
Combustion, does not take place at volcanoes, 2
Composite cones, 128, 161
Comstock mines, temperature of, 342
Concentric jointing in lava, 108, fig. 30
Cones composed of viscid lava, 129, fig. 43
— miniature on lava-streams, 100, 101, figs. 25, 26
— natural sections of, 129
— shifting of axis in, 167
Coolin Hills, Skye, 144
Cotopaxi, volcanic dust of, 69
— view of, 168, fig. 68
Craters, formation of, 82
— origin of, 167
— position of, 167
— fissuring of sides, 180
Crater of Stromboli, aperture at bottom of, 15
Crater-lakes, formation of, 171
— of Agnano, 171
— of Albano, 171
— of Avernus, 171
— of Bagno, 171, fig. 71
— of Bolsena, 171
— of Bracciano, 171
— of Frascati, 173, 175
— of Gustavila, 171, fig. 72
— of Laach, 171
— of Nemi, 171
Crater-rings, formation of, 170
Crater-ring of Somma, 177, fig. 76
Crater-ring of Pianura, 174
— — of Piano di Quarto, 174
— — of Vallariccia, 174
Creuzot, shafts at, 340
'Critical point' of liquids, 63
Crust of globe, definition of, 308
Crystals in lavas, 51
— — formed of crystallites, 54-57
— — formed in subterranean reservoirs, 60
— — interruption in growth of, 60
— pressure under which formed, 65
— deposited on surface of lava, 110
— porphyritic, origin of, 256
Crystalline minerals formed beneath volcanoes, 146, 147
— — ejected from volcanoes, 147
Crystallised minerals of volcanoes, 46
Crystallites, aggregates of, 54, Frontispiece
Crystallites in lavas, 53, Frontispiece
Crypto-crystalline base, 57
'Cupolas,' 135
Corral of Madeira, 209

DACITES, 198
Dana, Professor, J. D., cited, 100, 159, 291, 301, 327, 338, 339
Darwin, Mr., cited, 245, 246, 271, 289
Daubeny, cited, 182
Daubrée, M., cited, 147, 315, 320, 358
Daubréelite, 314
Davy, Sir Humphry, chemical theory of volcanoes, 344, 345
Deccan of India, 103
Density of the earth, 306
Denuded cones and craters, 158, fig. 59
Denudation, effects of, on volcanoes, 114
Deposits about volcanic fissures, 42
Detonations at Vesuvius, 26
Devonian volcanoes of British Islands, 274
Diorite, 59
Dolomieu, cited, 4, 39
Durocher, cited, 201
Dykes, formation of, 116, 117, 209, 210
— structure of rock in, 211
— pseudo-, 119
Dynamical theory of volcanoes, 347, 348

EARTH'S interior, nature of, 309
— — physical condition of, 325
— — hypothesis concerning, 328-330
— relation to other planets, 310, 311
Earthquakes, depth of origin of, 343, 344
— connection with volcanoes, 343
— accompanying Vesuvian eruption of 1872, 27
Ebullition, compared to volcanic eruptions, 19, 20
Eifel, volcanic cones of, 45
Ejected blocks, 45
— materials, height to which thrown, 72
— — stratification of, 117-119
Elements, pyroxenic and trachytic, theory of, 201
Elevation-craters, theory of, 135, 200
Erroneous opinions, sources of, in regard to volcanoes, 2
Eruptions, feeble and violent compared, 31
— prediction of, not possible, 32
— intervals between, 33
— of varying intensity, 33
— and barometric pressure, 36
— effects of repetition of from same fissure, 80
Eruptive action in sun and moon, 360-369
Etna, ideas of ancients concerning, 3
— and Anne Boleyn, 3
— observatory on, 37
— size of, 44
—, 151
— eruptions at summit and on flanks, 207
Etna, dyke and lava-stream in, 133, fig. 54
Etna, views of, 162, 163, figs. 62, 63
Euganean Hills, 139
— — volcanoes of, 201
Europe, volcanoes of, 227
Extra-terrestrial rocks, 316
Extra-terrestrial rocks, relation to ultra-basic rocks, 322, fig. 88

FELSTONES, 263
Ferric-chloride, mistaken for sulphur, 41
Fissure on flanks of Etna, 194, fig. 84
Fissure-eruptions, 188
Fissures, volcanic cones on, 194
— systems of, 198
Fingal's Cave, 106
Flames, phenomena mistaken for, 2
— at volcanoes, feebly luminous, 17
— false appearance of, in volcanoes, 17
Flames at volcanic vents, 41
Flashing lighthouse, compared to Stromboli, 10
Floods, accompanying volcanic outbursts, 30
Forbes, Mr. David, cited, 337, 339
Fossils, from beneath Vesuvius, 45
— supposed in basalt, 250
Fouqué, M., cited, 110, 213
Fumaroles, gases emitted from, 213
Fusiyama, form of, 90, 166
Fusiyama, 178, fig. 77

GABBRO, 59
Gardiner's river, travertine terraces of, 185
Gases emitted from volcanoes, 40
— — volcanic vents, 212-216
Geanticlinals, formation of, 297
Gems, formation of, 147
— mode of occurrence, 148
Geological continuity, doctrine of, 247
Geosynclinals, formation of, 294
Geysers, formation of, 217
— intermittent action of, 218
— of Colorado, 184, 217
— of Iceland, 184, 217
Giant's Causeway, 108
Gilbert, Mr. G. K., cited, 208
Girgenti, mud-volcanoes of, 182
Glass, formed by fusion of lavas, 52
Glasses, composed of certain silicates, 58
Glassy base, 57
Goethe, cited, 112
Graham Isle, 178, 179, fig. 78
Graham, cited, 345
Grand Sarcoui, Auvergne, 161
Granite, 59
Granite of Secondary and Tertiary ages, 254
Granitic rocks, position beneath volcanoes, 145
Great earth movements, nature of, 286
Great volcanic bands of the globe, 232-234
Grenelle, boring of, 341
Greystones, 49
Groundmass of lavas, 52
Grotto del Cane, 215
Guevo Upas, Java, 215
Guiscardi, Professor, referred to, 45
Gustavila, crater-lake of, 172, fig. 72

HAMILTON, Sir W., researches of, 4, 75, 84
— — observations on Vesuvius, 80
Hannay, Mr., referred to, 147
Hartley, Mr. Noel, referred to, 65
Hawaii, volcanoes of, 100, 125
— — lava-masses of, 159
— — volcanic eruptions at different levels, 327
Hebrides, volcanoes of, 271
Henry, Dr., cited, 355
Henry Mountains, Southern Utah, 208
Hephæstus, forge of, 3
Hochstetter, cited, 135, 356
Holosiderites, 315
Hopkins, Mr., cited, 349
Hot springs, numbers of, 219
Humboldt, researches of, 4
Hungary, lavas of, 96, 103
— volcanoes of, 126, 201
— deep wells of, 341
Hverfjall, Iceland, 178, fig. 77
Hydro-electric machine of Sir W. Armstrong, 29
Hypothesis, value of, 331-333

ICE under lava of Vesuvius in 1872, and of Etna, 110
Iceland, volcanic dust of, carried to Norway, 72
Indian Ocean, volcanoes in, 229
Insel Ferdinandez, 178, 179, fig. 78
Intermediate lavas, 48
Intervals between Eruptions, 33
Ireland, north-east of, 103
Iron in Ovifak-basalts, 319, fig. 87
Iron, seething of, 356
— of Ovifak, terrestrial origin of, 320
Ischia, eruption in 1301, 164
— crater-lake of Bagno in, 172, fig. 71
— plan of, 163, fig. 64
— parasitic cones in, 164, fig. 65
Island of Bourbon, 93
Isle Julie, 178, 179, fig. 78
Isogeotherms, 359

JANSSEN, referred to, 42
Joint-structures in lava, 104-110

KAMMERBÜHL, 112-114, fig. 33
— section of, 114, fig. 34
— section in side of, 118, fig. 36
Kant, nebular hypothesis of, 352
Kilauea, volcano of, 71, 138
— crater of, 181
King, Mr. Clarence, cited, 301

LAACHER SEE, minerals ejected at, 149
Lac Paven, Auvergne, 171, fig. 70
'Laccolites,' formation of, 208
Lago di Bolsena, 173, 175
Lago di Bracciano, dimensions of, 172, 173
Lake Avernus, 215
Lapilli, 70
Laplace, nebular hypothesis of, 325, 352
Lavas, action of acid gases on, 41
— resemblance to slags, 46
— chemical elements in, 46
— oxygen in, 47
— silicon in, 47
— proportion of silica and other oxides in, 47
— silicates in, 47
— acid, intermediate, basic, 48
— specific gravities of, 49
— colours of, 49
— microscopic study of, 50
— fusibility of, 51
— minerals in, 51
— artificially fused, 51
— crystals in, 51, 93
— ground mass of, 52
— crystalline forms of, 59
— of Bohemia, 103
— of Hungary, 96, 103
— of Kilauea, 95
— of Lipari, 96
— of Niedermendig, 103
— of Vesuvius, 104
— of Volvic, 95
— of Volcano, 95
— presence of water In, 102
— chemical deposits on, 110
— different fluidity of, 204
— augite and hornblende in, 267
Lava, cascade of, 93, fig. 18
Lava-cones, composed of liquid lava, 125
— — of viscid lava, 126, 127
— characters of, of liquid lava, 159
— — of viscid lava, 160
Lava-cones, outlines of, 160, fig. 60
Lava, in deep-seated reservoirs, 138
— consolidation of, at great depths, 139
Lava-fountains, 94
Lava-sheets, intrusive, 136, 137, fig. 56
'Lava' ornaments of Naples, 45
'Lava,' slow-cooling of, 110
— a bad conductor of heat, 110
— ice under, 110
Lava-streams, nature of movements, 92
— difference in liquidity of, 92
— miniature cones on, 100, 101
— vast dimensions of, 102
— structure of, 103
— position of columns in, 106
— sinking of surface of,