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 247Bailly, M., on the mountains of Mauritius 185Bald Head 260Banks’ Cove 234, 236Barn, The, St. Helena 216Basalt, specific gravity of 245Basaltic coast-mountains at Mauritiu 185—— at St. Helena 218—— at St. Jago 178Beaumont, M. Elie de, on circular subsidences in lava 233—— on dikes indicating elevation 228—— on inclination of lava-streams 227—— on laminated dikes 212Bermuda, calcareous rocks of 260, 262Beudant, M., on bombs 191—— on jasper 197—— on laminated trachyte 211—— on obsidian of Hungary 207—— on silex in trachyte 270, 197Bole 257Bombs, volcanic 189Bory St. Vincent, on bombs 190Boulders, absence in Australia and Cape of Good Hope 265Brattle island 238Brewster, Sir D., on a calcareo-animal substance 201—— on decomposed glass 252Brown, Mr. R., on extinct plants from Van Diemen’s land 257—— on sphærulitic bodies in silicified wood 207Buch, 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 171Feldspar, fusibility of 246—— in radiating crystals 263—— Labrador, ejected 193Feldspathic lavas 179—— at St. Helena 219—— rock, alternating with obsidian 202—— lamination, and origin of 209Fernando Noronha 181, 210Ferruginous superficial beds 259Fibrous calcareous matter at St. Jago 174Fissures of eruption 242, 249, 250Fitton, Dr., on calcareous breccia 262Flagstaff Hill, St. Helena 216Fleurian de Bellevue on sphærulites 207Fluidity of lavas 234, 235Forbes, Professor, on the structure of glaciers 212Fragments ejected at Ascension 192—— at the Galapagos archipelago 239Freshwater Bay 238, 243Fuerteventura (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 171Heat, action of, on calcareous matter 170Hennah, Mr., on ashes at Ascension 189Henslow, Prof., on chalcedony 197Hoffmann, on decomposed trachyte 182Holland, Dr., on Iceland 228Horner, Mr., on a calcareo-animal substance 201—— on fusibility of feldspar 246Hubbard, Dr., on dikes 247Humboldt on ejected fragments 193—— on obsidian formations 207, 209—— on parapets round craters 220—— on sphærulites 210Hutton on amygdaloids 176Hyalite in decomposed trachyte 182
Iceland, stratification of the circumferential hills 228Islands, volcanic, distribution of 248—— their elevation 250Incrustation, on St. Paul’s rocks 187Incrustations, calcareous, at Ascension 199
Jago, St. 167James island 234, 237, 242Jasper, origin of 196Jonnès, M. Moreau de, on craters affected by wind 189Juan Fernandez 250
Keilhau, M., on granite 264Kicker Rock 232King George’s sound 259
Labrador feldspar, ejected 193Lakes at bases of volcanoes 229Lamination of volcanic rocks 209Land-shells, extinct, at St. Helena 224Lanzarote, calcareous beds of 223Lava, adhesion to sides of a gorge 177—— feldspathic 179—— with cells semi-amygdaloidal 184Lavas, specific gravity of 243, 247Lava-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 189Lead, separation from silver 244Lesson, M., on craters at Ascension 189Leucite 234Lime, sulphate of, at Ascension 200Lonsdale, Mr., on fossil-corals from Van Diemen’s land 256Lot, St. Helena 221Lyell, 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 234Nelson, Lieut., on the Bermuda islands 260, 262New Caledonia 248New Red sandstone, cross cleavage of 253New South Wales 251New Zealand 259Nulliporæ (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 208Olivine decomposed at St. Jago 178—— at Van Diemen’s land 257—— in the lavas at the Galapagos archipelago 234Oolitic structure of recent calcareous beds at St. Helena 223Otaheite 183Oysters, 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 173Resin-like altered scoriæ 171Rio de Janeiro, gneiss of 252Robert, M., on strata of Iceland 228Rogers, 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 183Talus, stratified, within tuff craters 236Terceira 182Tertiary deposit of St. Jago 169Trachyte, 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 195Trap-dikes in the plutonic series 247—— at King George’s sound 259Travertin at Van Diemen’s land 257Tropic-bird, now rare, at St. Helena 225Tuff, craters of 231, 235, 236—— their breached state 240—— peculiar kind of 231Turner, Mr., on the separation of molten metals 244Tyerman and Bennett on marine remains at Huaheine 184
Valleys, gorge-like, at St. Helena 225—— in New South Wales 254—— in St. Jago 180Van Diemen’s land 256Veins in trachyte 195—— of jasper 195Vincent, Bory St., on bombs 190Volcanic bombs 189—— island in process of formation in the Atlantic 226—— islands, their distribution 248
Wacke, its passage into lava 183, 257Wackes, argillaceous 168, 178Webster, Dr., on a basin-formed island 237—— on gypsum at Ascension 201White, Martin, on soundings 254Wind, effects of, on the form of craters

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