111
'Lave di fango,' 30
'Lave di fuoco,' 30
Lawrencite, 314
Laws of volcanic action, 38
Le Conte, cited, 347
Leucite, absence from ancient lavas, 268
Lightning, accompanying volcanic outbursts, 28
Linear arrangement of volcanic vents, 191
— — of volcanoes, 231
Lipari Islands, 3, 39
— — fissures in, 197
— — pumice-cones in, 154
— — order of appearance of lavas in, 200
— — breached pumice-cones in, 124, fig. 41
— — map of, 192, fig. 81
— — lavas of, 96, figs. 20, 21
Liquids in cavities of crystals, 63
Liquid cavities in lavas, 60, fig. 7
— — spontaneous movement of bubbles in, 62, fig. 8
— — spontaneous movement of bubbles in, cause of, 65
Lockyer, Mr. Norman, cited, 322, 363, 364
Lunar craters, 368, fig. 95
Lyell, Sir Charles, cited, 135, 167, 197

MACCULLOCH, cited, 207, 208
Madeira, cliff-section in, 128, fig. 47
Magmas, theory of, 201
— objections to, 202, 203
Mallet, Mr., cited, 269, 343, 346
Mamelons of Bourbon, 126, 127, figs. 45, 46
Maskelyne, Professor, cited, 314
Massa di Somma, destruction of, 26
Mauna Loa, 138
Metamorphism around volcanic vents, 145
Meteorites, nature of, 312
— composition of, 313
— minerals of, 314
— classification of, 315
Melaphyres, 262
Miascite, 59
Michel Lévy, M., 110
Micro-crystalline base, 58
Microliths. See Crystallites
Microscopic study of lavas, 50
Minerals in lavas, 51
— of Vesuvius, 46
Mineral-veins, formation of, 149
— connection with volcanoes, 220
— nature of materials in, 321
Misenum, Cape of, section of tuff-cone of, 121, fig. 38
Modena, mud-volcanoes of, 182
Mont Dore, section at, 130, fig. 48
Monte Cerboli, Tuscany, 216
Monte Massi, Tuscany, well at, 341
Monte Nuovo, history of formation of, 76
— — description of, 77, 78, fig. 10
— — 152
— — crater of, 168
— — production of fissure at, 190
Monte Rotondo, Tuscany, 216
Moon, effect of internal forces on, 305
Mountains, all volcanoes not, 2
Mountain-chains, formation of, 291
— — all of recent date, 292
Mud-streams at volcanoes, 30
Mud-volcanoes, formation of, 181, 182
Mull, dissected volcano of, 142-4, figs. 57, 58
Muscovite, absence of, from modern lavas, 268

NEBULAR hypothesis of Laplace, 325, 352
— — of Kant, 352
New Zealand, geysers of, 217
— — volcanoes of, 135
— — volcanic cones in, 79
Niedermendig, lava of, 103
Nordenskiöld, Professor, cited, 318

OBSERVATORY on Vesuvius, 24, 37
— on Etna, 37
Obsidian, 59
Oceans, depth of, in volcanic areas, 242
Oceanic islands, volcanoes in, 228
Oliver, Capt. S. P., 92
Oldhamite, 314
Outlines of Vesuvius, 87, fig. 17
Ovifak, iron-masses of, 319
Oxidation of materials of globe, 324
Oxygen, proportion in lavas, 47

PACIFIC, volcanoes in, 229
Palmieri, Professor, cited, 25, 37
Papandayang, eruption of, 169
Papin's digester, nature of action in, 22
Parasitic cones, formation of, 161, 162, fig. 61
Pele's Hair, 71
Perlitic structure, 109
Phillips, Mr. J. A., cited, 220
Phonolites, 50, 59
Phonolite-volcanoes, 126
Photograph of Vesuvius eruption, 24, fig. 5
'Pine-tree, appendage of Vesuvius, 29
Pitchstones, porphyritic, 60
Plateaux formed of lava-sheets, 270
Pliny, Elder, death of, 7
Plombières, hot springs of, 147
Plutonic rocks, 61
Pompeii, nature of materials covering, 117
Ponza Islands, 39
Ponza, sections in, 131, 132, figs. 51, 52
Porphyrites, 263
Porphyritic pitchstones, 60
Potentially liquid rock, 250
Pre-Cambrian volcanoes of British Islands, 274
Presence of water in lavas, 353
Pressure under which crystals were formed, 65
Predazzo, ancient volcano of, 165, fig. 67
Propylites, 199
Pseudo-dykes, 119
Pumice, how formed, 68
— cause of white colour of, 71
— floating on ocean, 73
— on ocean-beds, 73
Pumice-cones, 154
Puy de Pariou, Auvergne, 193, 194, figs. 82, 83
Puzzolana, 89

RAIN, accompanying volcanic outbursts, 30
Rate of movement of lava-streams, 97
Rath, Professor Vom, 72
Red clay of ocean-beds, 74
Red Mountains, Skye, 144
Reservoirs beneath volcanoes, 145
Reyer, Dr. Ed., experiments of, 125, 160
Reykjanes, eruption of, in 1783, 102
Rhyolites, 50, 59
Richthofen, Von, cited, 196, 199, 200, 205
Rocca-Monfina, 178, fig. 77
— —, 204
Rock-masses, movements of, 288
Rocky Mountains, 103
— — volcanoes of, 201
Rotomahana, sinter-terraces of, 185
Ropy-lavas, 98, fig. 24

SALINA, section in, 132, fig. 53
Sandwich Islands, lavas of, 125
San Sebastiano, destruction of, 26
San Stephano, section in, 131, fig. 50
Santorin, 42
Sarcoui, Grand Puy of, 126, fig. 44
Sciarra del fuoco, 13
Scoria, how formed, 68, 70
Scoria-cones, altered by acid gas, 155
— breached, 156
— characters of, 153
— preservation of, 155
— red colour of, 154
Scoria-cone in Vesuvius, 122, fig. 39
Scoria-cone near Auckland, N. Z., 165, fig. 66
Schmidt, referred to, 153
Schreibersite, 314
Scrope, Mr. Poulett, cited, 5, 69, 106, 135, 198, 205, 212, 238, 289
Sea of Azof, mud-volcanoes of, 182
Secchi, Father, cited, 362
Shiant Isles, 105
Silica, presence in lavas, 47
Silicates in lavas, 47
Silicon, proportion in lavas, 47
Siliceous sinter, deposits of, 220
Silver, spitting of, 355
Silvestri, Professor, cited, 230
Similarity of lavas of different ages, 260
Sinter-cones, forms of, 183, fig. 79
Skye, dissected volcano of, 144
Slags, compared with lavas, 46
Smith, Lawrence, cited, 320
Smoke, appearance of, due to steam, 2
Snowdon, 274
Solar prominences, 364-366, figs. 92, 93, 94
Solfatara of Naples, 214
Solfatara-stage of volcanoes, 215
Somma, 133
— crater-ring of, 83
Sorby, Mr. H. C., referred to, 59, 252
Spallanzani, early researches of, 4
— observations on Stromboli, 8
— cited, 39, 367
Specific gravities of lavas, 49
— — of glassy and crystalline rocks, 59
Spectroscope in vulcanology, 41
Spectrum-analysis, results of, 311
Specular-iron, deposited on lava-streams, 110
Sperenberg, boring of, 341
Sphærulites, 54, Frontispiece
Sporadosiderites, 316
Stability of crust of globe, 326
Staffa, Isle of, 106
Steenstrup, cited, 319
Steam-engine compared to volcano, 8
Steam, emitted by lava of Vesuvius, 27
Sternberg, referred to, 113
St. Kilda, 181
Stokes, Professor, 65
St. Paul, Island of, 180
Stromboli, 42, 158
— apertures at bottom of crater, 15
— appearances in crater of, 16
— — at night, 10
— compared with Vesuvius, 23
— crater of, 13
— dependence of eruptions on atmospheric conditions, 34
— eruption of, 14, fig. 4
— general features of, 11
— map of, 11, fig. 2
— observations by Spallanzani, 8
— resemblance to flashing light, 10
— section of, 13, fig. 8
— soundings around, 12
— vapour-cloud above, 9
— violent eruptions of, 23
Strombolian stage, 23
Stufas, nature of, 217
Submarine volcanoes, 179
Subterranean forces, beneficial effects of, 303
Subsidence in centre of volcanoes, 165
Sulphur, absorption of water by molten, 356
— deposited on lava-streams, 110
— how formed at volcanoes, 18
— not the cause of volcanic outbursts, 18
Surfaces of lava-streams, 97-99, figs. 22, 23
Sun-spots, 361-363, figs. 89, 90, 91
Syenite, 59
Syssiderites, 316
Szabo, Professor, cited, 199

TACHYLYTE, 59
Tertiary volcanoes of British Islands, 276
Terraces, sinter- and travertine-formation of, 185, fig. 80
Temperature, increase in deeper parts of earth's crust, 335
— rate of increase in different areas, 340
Teneriffe, 44, 151
Teneriffe, 178, fig. 77
— peak of, 175, fig. 73
Tenon-and-mortise structure in basaltic columns, 107
Theodosius and Vulcano, 3
Thunder, accompanying volcanic outbursts, 28
Trachytes, 49, 50, 69
Trap-rocks, origin of, 241
Trass, 90
Travertine or Tibur-stone, 184
— deposits of, 220
Triassic volcanoes of British Islands, 275
Tridymite deposited on lava-streams, 110
Troilite, 314
Troost, cited, 355
Tufa, or tuff, 90
Tuff-cones, character of, 157
— denudation of, 157, 158
Typhon, fable of, 3

ULTRA-BASIC lavas, 50, 66
— rocks, 317

VAL DEL BOVE, Etna, 133, 180, 209
— — dykes in, 134, fig. 55
Vapour-cloud over Vesuvius, 26, 29
— — Stromboli, 9
Ventotienne, Island of, section at, 130, fig. 49
Vesuvius, 37
— changes in form of, 81
— compared with Stromboli, 23
— crater of in 1756, 84, fig. 14
— — of in 1767, 85, fig. 16
— — of in 1822, 82, fig. 13
— — of in 1843, 86, fig. 16
— detonations at, 26
— early history of, 83
— eruption of year 79, 84
— — of 1822, 69
— — of April 1872, 24
— — of October 1822, 24
— ejected blocks of, 45
— first eruption of, 7
— form of, 166
— fossils of, 45
— growth of cone of, 80
— history of, 204
— last eruption of, 7
— lava-stream of 1855, 101
— lava-streams of 1858, 1872, 97
— lavas of, 104
— minerals of, 46
— — ejected at, 149
— observatory on, 24, 37
— outlines of, 87
— pine-tree appendage of, 29
— scoria-cones in lava, 122
— — on lava of 1855, 153
— steam emitted by lava of, 27
— vapour-cloud over, 26, 29
Vesuvian stage, 23
— eruption, photograph of, 24, fig. 5
Viscid lavas of Lipari Islands, 94-96
Vitreous lavas, devitrification of, 259
Volcanic action, laws of, 32
— bombs, 70, 71
— cycles, nature of, 221, 222
— — duration of, 223
— cones, internal structure of, 115-122
— — experimental illustration of formation of, 120, fig. 37
— — limits to height of, 166
— — form of, 152
— — dimensions of, 152
— — irregular development of, 90
— — slopes of sides of, 91
— — composed of ejected rock-fragments, 156
— — curved slopes of, 156
— débris on sea-bottom, 240
— dust, fineness of, 69
— districts, areas of upheaval, 245
— ejections, alteration of, 258
— eruptions, compared to ebullition, 19, 20
— forces, compensate for denudation, 283
— — intensity at former periods, 278
— — necessity for action of, 285
— — shifting of from one area to another, 277
— mountains, origin of conical forms, 89
— — mode of growth, 89
— phenomena of the past similar to those at present, 273
— products, order of appearance of, 198, 199
Volcanic rocks, 61
— — similarity of ancient and modern, 253
Volcano, origin of name, 3
— craters of, 167
— Island of. See Vulcano.
— compared to steam-engine, 8
Volcanoes, blocks, ejected from, 45
— built up of ejected fragments, 74
— destruction caused by, 281
— dissected by denudation, 115, 139
— erroneous ideas concerning, 1
— ejection of different materials from, 205
— known to ancients, 3
— life-history of, 186
— number of, 224, 225
— of Africa, 227
— of America, 236
— of Asia, 236
— of Bohemia, 126
— of Central Asia, 236
— of Central Pacific, 236
— of Europe, 227
— of Hungary, 126
— position in relation to mountain chains, 243
— popular ideas concerning, 1
— reservoirs beneath, 145
Volvic lava of, 103
Vose, cited, 346
Vulcan, forge of, 3
Vulcano, island of, 3, 158
Vulcano and Theodosius, 3
Vulcano, 178, fig. 77
— and Vulcanello, view of, 43, fig. 6
— chemical deposits at, 44
— eruption in 1786, 43
— — in 1873, 43
— — lava-stream in, 95, fig. 19
— —, 103, fig. 27
— plan of, 195,