INDEX TO VOLCANIC ISLANDS.
Abel, M., on calcareous casts at the Cape of Good Hope 261
Abingdon island 234
Abrolhos islands, incrustation on 188
Aeriform explosions at Ascension 191
Albatross, driven from St. Helena
225
Albemarle island 234
Albite, at the Galapagos archipelago
234
Amygdaloidal cells, half filled 184
Amygdaloids, calcareous origin of 176
Ascension, arborescent incrustation on rocks of 188
—— absence of dikes, freedom from volcanic action, and
state of lava-streams 226
Ascidia, extinction of 258
Atlantic Ocean, new volcanic focus in
226
Augite, fused 239
Australia 251
Azores 182,
248
Bahia in Brazil, dikes at 247
Bailly, M., on the mountains of Mauritius
185
Bald Head 260
Banks’ Cove 234,
236
Barn, The, St. Helena 216
Basalt, specific gravity of 245
Basaltic coast-mountains at Mauritiu
185
—— at St. Helena 218
—— at St. Jago 178
Beaumont, M. Elie de, on circular subsidences in lava 233
—— on dikes indicating elevation
228
—— on inclination of lava-streams
227
—— on laminated dikes 212
Bermuda, calcareous rocks of 260, 262
Beudant, M., on bombs 191
—— on jasper 197
—— on laminated trachyte
211
—— on obsidian of Hungary
207
—— on silex in trachyte 270, 197
Bole 257
Bombs, volcanic 189
Bory St. Vincent, on bombs 190
Boulders, absence in Australia and Cape of Good Hope 265
Brattle island 238
Brewster, Sir D., on a calcareo-animal substance 201
—— on decomposed glass 252
Brown, Mr. R., on extinct plants from Van Diemen’s land 257
—— on sphærulitic bodies in silicified wood 207
Buch, Von, on cavernous lava 233
—— on central volcanoes 249
—— on crystals sinking in obsidian
243
—— on laminated lava 209
—— on obsidian streams 208
—— on olivine in basalt 234
—— on superficial calcareous beds in the Canary islands
224
Calcareous deposit at St. Jago affected by heat 169, 171
—— fibrous matter, entangled in streaks in scoriæ
174
—— freestone at Ascension
198
—— incrustations at Ascension
199
—— sandstone at St. Helena
222
—— superficial beds at King George’s sound 260
Cape of Good Hope 263
Carbonic acid, expulsion of, by heat 171,
176
Carmichael, Capt., on glassy coatings to dikes 216
Casts, calcareous, of branches 261
Chalcedonic nodules 257
Chalcedony in basalt and in silicified wood
196
Chatham island 231,
235, 241, 248,
259
Chlorophæite 257
Clarke, Rev. W., on the Cape of Good Hope
258, 263
Clay-slate, its decomposition and junction with granite at the
Cape of Good Hope 264
Cleavage of clay-slate in Australia
252
Cleavage, cross, in sandstone 253
Coast denudation at St. Helena 226
Columnar basalt 173
“Comptes Rendus,” account of volcanic phenomena in the Atlantic 226
Concepcion, earthquake of 228, 249
Concretions in aqueous and igneous rocks compared 206
—— in tuff 197
—— of obsidian 206, 208
Conglomerate, recent, at St. Jago 181
Coquimbo, curious rock of 261
Corals, fossil, from Van Diemen’s Land
256
Crater, segment of, at the Galapagos
238
—— great central one at St. Helena
219
—— internal ledges round, and parapet on 220
Craters, basaltic, at Ascension 189
—— form of, affected by the trade wind 189
—— of elevation 227
—— of tuff at Terceira 182
—— of tuff at the Galapagos archipelago 230, 231, 235, 237
—— their breached state 240
—— small basaltic at St. Jago
177
—— —— at the Galapagos archipelago 232
Crystallisation favoured by space 211
Dartigues, M., on sphærulites
207
Daubeny, Dr., on a basin-formed island
237
—— on fragments in trachyte
193
D’Aubuisson on hills of phonolite 222
—— on the composition of obsidian
206
—— on the lamination of clay-slate
210
De la Beche, Sir H., on magnesia in erupted lime 174
—— on specific gravity of limestones 198
Denudation of coast at St. Helena 226
Diana’s Peak, St. Helena 220
Dieffenbach, Dr., on the Chatham Islands
259
Dikes, truncated, on central crateriform ridge of St. Helena 219
—— at St. Helena; number of; coated by a glossy layer;
uniform thickness of 216
—— great parallel ones at St. Helena 222
—— not observed at Ascension
226
—— of tuff 231
—— of trap in the plutonic series
247
—— remnants of, extending far into the sea round St.
Helena 226
Dislocations at Ascension 192
—— at St. Helena 217, 221
Distribution of volcanic islands 248
Dolomieu, on decomposed trachyte 182
—— on laminated lava 210, 211
—— on obsidian 208
Drée, M., on crystals sinking in lava
243
Dufrenoy, M., on the composition of the surface of certain
lava-streams 209,
243
—— on the inclination of tuff-strata 236
Eggs of birds embedded at St. Helena
224
—— of turtle at Ascension
198
Ejected fragments at Ascension 192
—— at the Galapagos archipelago
239
Elevation of St. Helena 225
—— the Galapagos archipelago
241
—— Van Diemen’s Land, Cape of Good Hope, New Zealand,
Australia, and Chatham island 258
—— of volcanic islands 250
Ellis, Rev. W., on ledges within the great crater at Hawaii 220
—— on marine remains at Otaheite
184
Eruption, fissures of 224, 249, 250
Extinction of land-shells at St. Helena
224
Faraday, Mr., on the expulsion of carbonic acid gas 171
Feldspar, fusibility of 246
—— in radiating crystals
263
—— Labrador, ejected 193
Feldspathic lavas 179
—— at St. Helena 219
—— rock, alternating with obsidian
202
—— lamination, and origin of
209
Fernando Noronha 181,
210
Ferruginous superficial beds 259
Fibrous calcareous matter at St. Jago
174
Fissures of eruption 242, 249, 250
Fitton, Dr., on calcareous breccia 262
Flagstaff Hill, St. Helena 216
Fleurian de Bellevue on sphærulites
207
Fluidity of lavas 234, 235
Forbes, Professor, on the structure of glaciers 212
Fragments ejected at Ascension 192
—— at the Galapagos archipelago
239
Freshwater Bay 238,
243
Fuerteventura (Feurteventura), calcareous beds of 224
Galapagos archipelago 229
—— parapets round craters
220
Gay Lussac, on the expulsion of carbonic acid gas 171
Glaciers, their structure 212
Glossiness of texture, origin of 206
Gneiss, derived from clay-slate 264
—— with a great embedded fragment
252
Gneiss-granite, form of hills of 259
Good Hope, Cape of 263
Gorges, narrow, at St. Helena 225
Granite, junction with clay-slate, at the Cape of Good Hope 263
Granitic ejected fragments 192, 239
Gravity, specific, of lavas 243-8
Gypsum, at Ascension 201
—— in volcanic strata at St. Helena 215
—— on surface of the ground at ditto 223
Hall, Sir J., on the expulsion of carbonic acid gas 171
Heat, action of, on calcareous matter
170
Hennah, Mr., on ashes at Ascension 189
Henslow, Prof., on chalcedony 197
Hoffmann, on decomposed trachyte 182
Holland, Dr., on Iceland 228
Horner, Mr., on a calcareo-animal substance
201
—— on fusibility of feldspar
246
Hubbard, Dr., on dikes 247
Humboldt on ejected fragments 193
—— on obsidian formations 207,
209
—— on parapets round craters
220
—— on sphærulites 210
Hutton on amygdaloids 176
Hyalite in decomposed trachyte 182
Iceland, stratification of the circumferential hills 228
Islands, volcanic, distribution of 248
—— their elevation 250
Incrustation, on St. Paul’s rocks 187
Incrustations, calcareous, at Ascension
199
Jago, St. 167
James island 234,
237, 242
Jasper, origin of 196
Jonnès, M. Moreau de, on craters affected by wind 189
Juan Fernandez 250
Keilhau, M., on granite 264
Kicker Rock 232
King George’s sound 259
Labrador feldspar, ejected 193
Lakes at bases of volcanoes 229
Lamination of volcanic rocks 209
Land-shells, extinct, at St. Helena
224
Lanzarote, calcareous beds of 223
Lava, adhesion to sides of a gorge 177
—— feldspathic 179
—— with cells semi-amygdaloidal
184
Lavas, specific gravity of 243, 247
Lava-streams blending together at St. Jago
177
—— composition of surface of
208
—— differences in the state of their surfaces 244
—— extreme thinness of 238
—— heaved up into hillocks at the Galapagos archipelago
233
—— their fluidity 234, 235
—— with irregular hummocks at Ascension 189
Lead, separation from silver 244
Lesson, M., on craters at Ascension
189
Leucite 234
Lime, sulphate of, at Ascension 200
Lonsdale, Mr., on fossil-corals from Van Diemen’s land 256
Lot, St. Helena 221
Lyell, Mr., on craters of elevation
227
—— on embedded turtles’ eggs
198
—— on glossy coating to dikes
216
Macaulay, Dr., on calcareous casts at Madeira
262
MacCulloch, Dr., on an amygdaloid 184
—— on chlorophæite
287
—— on laminated pitchstone
209
Mackenzie, Sir G., on cavernous lava-streams
233
—— on glossy coatings to dikes
216
—— on obsidian streams 208
—— on stratification in Iceland
228
Madeira, calcareous casts at 262
Magazine, Nautical,—account of volcanic phenomena in
the Atlantic 226
Marekanite 206
Mauritius, crater of elevation of 184, 227
Mica, in rounded nodules 168
—— origin in metamorphic slate
264
—— radiating form of 263
Miller, Prof., on ejected Labrador feldspar
193
—— on quartz crystals in obsidian beds 202
Mitchell, Sir T., on bombs 191
—— on the Australian valleys
254
Mud streams at the Galapagos archipelago
236
Narborough island 234
Nelson, Lieut., on the Bermuda islands
260, 262
New Caledonia 248
New Red sandstone, cross cleavage of
253
New South Wales 251
New Zealand 259
Nulliporæ (fossil), resembling concretions 169
Obsidian, absent at the Galapagos archipelago
241
—— bombs of 191
—— composition and origin of
207, 208
—— crystals of feldspar sink in
243
—— its irruption from lofty craters 246
—— passage of beds into 202
—— specific gravity of 243, 246
—— streams of 208
Olivine decomposed at St. Jago 178
—— at Van Diemen’s land 257
—— in the lavas at the Galapagos archipelago 234
Oolitic structure of recent calcareous beds at St. Helena 223
Otaheite 183
Oysters, extinction of 258
Panza islands, laminated trachyte of
209
Pattinson, Mr., on the separation of lead and silver 244
Paul’s, St., rocks of 187
Pearlstone 206
Peperino 232
Péron, M., on calcareous rocks of Australia 262, 263
Phonolite, hills of 179, 181, 221
—— laminated 210
—— with more fusible hornblende
246
Pitchstone 204
—— dikes of 209
Plants, extinct 257
Plutonic rocks, separation of constituent parts of, by gravity 246
Porto Praya 167
Prevost, M. C., on rarity of great dislocations in volcanic
islands 217
Prosperous hill, St. Helena 218
Pumice, absent at the Galapagos archipelago
241
—— laminated 209, 210, 211
Puy de Dome, trachyte of 193
Quail island, St. Jago 168, 170, 173
Quartz, crystals of, in beds alternating with obsidian 202
—— crystallised in sandstone
252
—— fusibility of 246
—— rock, mottled from metamorphic action with earthy
matter 170
Red hill 173
Resin-like altered scoriæ 171
Rio de Janeiro, gneiss of 252
Robert, M., on strata of Iceland 228
Rogers, Professor, on curved lines of elevation 249
Salses, compared with tuff craters 240
Salt deposited by the sea 200
—— in volcanic strata 201, 215
—— lakes of, in craters 240
Sandstone of Brazil 265
—— of the Cape of Good Hope
265
—— platforms of, in New South Wales 252, 265
Schorl, radiating 263
Scrope, Mr. P., on laminated trachyte 209,
210, 212
—— on obsidian 208
—— on separation of trachyte and basalt 244
—— on silex in trachyte 176
—— on sphærulites 210
Seale, Mr., geognosy of St. Helena 215
—— on dikes 226
—— on embedded birds’ bones
225
Seale, on extinct shells of St. Helena
224
Sedgwick, Professor, on concretions
206
Septaria, in concretions in tuff 198
Serpulæ on upraised rocks 185
Seychelles 248
Shells, colour of, affected by light
201
—— from Van Diemen’s land
256
—— land, extinct, at St. Helena
224
—— particles of, drifted by the wind at St. Helena 223
Shelly matter deposited by the waves
200
Siau, M., on ripples 254
Signal Post Hill 168,
175, 176
Silica, deposited by steam 182
—— large proportion of, in obsidian 206, 208
—— specific gravity of 246
Siliceous sinter 196
Smith, Dr. A., on junction of granite and clay-slate 264
Spallanzani on decomposed trachyte 182
Specific gravity of recent calcareous rocks and of limestone 198
—— of lavas 245
Sphærulites in glass and in silicified wood 207
—— in obsidian 204, 210
Sowerby, Mr. G. B., on fossil-shells from Van Diemen’s land 256
—— from St. Jago 169
—— land-shells from St. Helena
224
St. Helena 214
—— crater of elevation of
227
St. Jago, crater of elevation of 227
—— effects of calcareous matter on lava 231
St. Paul’s rocks 187,
248
Stokes, Mr., collections of sphærulites and of obsidians 207, 212
Stony-top, Little 218, 222
—— Great 218
Stratification of sandstone in New South Wales 253, 255
Streams of obsidian 208
Stutchbury, Mr., on marine remains at Otaheite 184
Subsided space at Ascension 192
Tahiti 183
Talus, stratified, within tuff craters
236
Terceira 182
Tertiary deposit of St. Jago 169
Trachyte, absent at the Galapagos archipelago
241
—— at Ascension 193
—— at Terceira 182
—— decomposition of, by steam
182
—— its lamination 200, 210
—— its separation from basalt
244
—— softened at Ascension
194
—— specific gravity of 245
—— with singular veins 195
Trap-dikes in the plutonic series 247
—— at King George’s sound
259
Travertin at Van Diemen’s land 257
Tropic-bird, now rare, at St. Helena
225
Tuff, craters of 231,
235, 236
—— their breached state 240
—— peculiar kind of 231
Turner, Mr., on the separation of molten metals 244
Tyerman and Bennett on marine remains at Huaheine 184
Valleys, gorge-like, at St. Helena 225
—— in New South Wales 254
—— in St. Jago 180
Van Diemen’s land 256
Veins in trachyte 195
—— of jasper 195
Vincent, Bory St., on bombs 190
Volcanic bombs 189
—— island in process of formation in the Atlantic 226
—— islands, their distribution
248
Wacke, its passage into lava 183, 257
Wackes, argillaceous 168, 178
Webster, Dr., on a basin-formed island
237
—— on gypsum at Ascension
201
White, Martin, on soundings 254
Wind, effects of, on the form of craters