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Abel, M., on calcareous casts at the Cape of Good Hope.

Abingdon island.

Abrolhos islands, incrustation on.

Aeriform explosions at Ascension.

Albatross, driven from St. Helena.

Albemarle island.

Albite, at the Galapagos archipelago.

Amygdaloidal cells, half filled.

Amygdaloids, calcareous origin of.

Ascension, arborescent incrustation on rocks of.
-absence of dikes, freedom from volcanic action, and state of lava-streams.

Ascidia, extinction of.

Atlantic Ocean, new volcanic focus in.

Augite, fused.



Bahia in Brazil, dikes at.

Bailly, M., on the mountains of Mauritius.

Bald Head.

Banks' Cove.

Barn, The, St. Helena.

Basalt, specific gravity of.

Basaltic coast-mountains at Mauritius.
-at St. Helena.
-at St. Jago.

Beaumont, M. Elie de, on circular subsidences in lava.
-on dikes indicating elevation.
-on inclination of lava-streams.
-on laminated dikes.

Bermuda, calcareous rocks of.

Beudant, M., on bombs.
-on jasper.
-on laminated trachyte.
-on obsidian of Hungary.
-on silex in trachyte.


Bombs, volcanic.

Bory St. Vincent, on bombs.

Boulders, absence in Australia and Cape of Good Hope.

Brattle island.

Brewster, Sir D., on a calcareo-animal substance.
-on decomposed glass.

Brown, Mr. R., on extinct plants from Van Diemen's land.
-on sphaerulitic bodies in silicified wood.

Buch, Von, on cavernous lava.
-on central volcanoes.
-on crystals sinking in obsidian.
-on laminated lava.
-on obsidian streams.
-on olivine in basalt.
-on superficial calcareous beds in the Canary islands.

Calcareous deposit at St. Jago affected by heat.
-fibrous matter, entangled in streaks in scoriae.
-freestone at Ascension.
-incrustations at Ascension.
-sandstone at St. Helena.
-superficial beds at King George's sound.

Cape of Good Hope.

Carbonic acid, expulsion of, by heat.

Carmichael, Capt., on glassy coatings to dikes.

Casts, calcareous, of branches.

Chalcedonic nodules.

Chalcedony in basalt and in silicified wood.

Chatham island.


Clarke, Rev. W., on the Cape of Good Hope.

Clay-slate, its decomposition and junction with granite at the Cape of Good

Cleavage of clay-slate in Australia.

Cleavage, cross, in sandstone.

Coast denudation at St. Helena.

Columnar basalt.

"Comptes Rendus," account of volcanic phenomena in the Atlantic.

Concepcion, earthquake of.

Concretions in aqueous and igneous rocks compared.
-in tuff.
-of obsidian.

Conglomerate, recent, at St. Jago.

Coquimbo, curious rock of.

Corals, fossil, from Van Diemen's Land.

Crater, segment of, at the Galapagos.
-great central one at St. Helena.
-internal ledges round, and parapet on.

Craters, basaltic, at Ascension.
-form of, affected by the trade wind.
-of elevation.
-of tuff at Terceira.
-of tuff at the Galapagos archipelago.
-their breached state.
-small basaltic at St. Jago.
--at the Galapagos archipelago.

Crystallisation favoured by space.

Dartigues, M., on sphaerulites.

Daubeny, Dr., on a basin-formed island.
-on fragments in trachyte.

D'Aubuisson on hills of phonolite.
-on the composition of obsidian.
-on the lamination of clay-slate.

De la Beche, Sir H., on magnesia in erupted lime.
-on specific gravity of limestones.

Denudation of coast at St. Helena.

Diana's Peak, St. Helena.

Dieffenbach, Dr., on the Chatham Islands.

Dikes, truncated, on central crateriform ridge of St. Helena.
-at St. Helena; number of; coated by a glossy layer; uniform thickness of.
-great parallel ones at St. Helena.
-not observed at Ascension.
-of tuff.
-of trap in the plutonic series.
-remnants of, extending far into the sea round St. Helena.

Dislocations at Ascension.
-at St. Helena.

Distribution of volcanic islands.

Dolomieu, on decomposed trachyte.
-on laminated lava.
-on obsidian.

Dree, M., on crystals sinking in lava.

Dufrenoy, M., on the composition of the surface of certain lava-streams.
-on the inclination of tuff-strata.

Eggs of birds embedded at St. Helena.
-of turtle at Ascension.

Ejected fragments at Ascension.
-at the Galapagos archipelago.

Elevation of St. Helena.
-the Galapagos archipelago.
-Van Diemen's Land, Cape of Good Hope, New Zealand, Australia, and Chatham
-of volcanic islands.

Ellis, Rev. W., on ledges within the great crater at Hawaii.
-on marine remains at Otaheite.

Eruption, fissures of.

Extinction of land-shells at St. Helena.

Faraday, Mr., on the expulsion of carbonic acid gas.

Feldspar, fusibility of.
-in radiating crystals.
-Labrador, ejected.

Feldspathic lavas.
-at St. Helena.
-rock, alternating with obsidian.
-lamination, and origin of.

Fernando Noronha.

Ferruginous superficial beds.

Fibrous calcareous matter at St. Jago.

Fissures of eruption.

Fitton, Dr., on calcareous breccia.

Flagstaff Hill, St. Helena.

Fleurian de Bellevue on sphaerulites.

Fluidity of lavas.

Forbes, Professor, on the structure of glaciers.

Fragments ejected at Ascension.
-at the Galapagos archipelago.

Freshwater Bay.

Fuerteventura (Feurteventura), calcareous beds of.

Galapagos archipelago.
-parapets round craters.

Gay Lussac, on the expulsion of carbonic acid gas.

Glaciers, their structure.

Glossiness of texture, origin of.

Gneiss, derived from clay-slate.
-with a great embedded fragment.

Gneiss-granite, form of hills of.

Good Hope, Cape of.

Gorges, narrow, at St. Helena.

Granite, junction with clay-slate, at the Cape of Good Hope.

Granitic ejected fragments.

Gravity, specific, of lavas.

Gypsum, at Ascension.
-in volcanic strata at St. Helena.
-on surface of the ground at ditto.

Hall, Sir J., on the expulsion of carbonic acid gas.

Heat, action of, on calcareous matter.

Hennah, Mr., on ashes at Ascension.

Henslow, Prof., on chalcedony.

Hoffmann, on decomposed trachyte.

Holland, Dr., on Iceland.

Horner, Mr., on a calcareo-animal substance.
-on fusibility of feldspar.

Hubbard, Dr., on dikes.

Humboldt on ejected fragments.
-on obsidian formations.
-on parapets round craters.
-on sphaerulites.

Hutton on amygdaloids.

Hyalite in decomposed trachyte.

Iceland, stratification of the circumferential hills.

Islands, volcanic, distribution of.
-their elevation.

Incrustation, on St. Paul's rocks.

Incrustations, calcareous, at Ascension.

Jago, St.

James island.

Jasper, origin of.

Jonnes, M. Moreau de, on craters affected by wind.

Juan Fernandez.

Keilhau, M., on granite.

Kicker Rock.

King George's sound.

Labrador feldspar, ejected.

Lakes at bases of volcanoes.

Lamination of volcanic rocks.

Land-shells, extinct, at St. Helena.

Lanzarote, calcareous beds of.

Lava, adhesion to sides of a gorge.
-with cells semi-amygdaloidal.

Lavas, specific gravity of.

Lava-streams blending together at St. Jago.
-composition of surface of.
-differences in the state of their surfaces.
-extreme thinness of.
-heaved up into hillocks at the Galapagos archipelago.
-their fluidity.
-with irregular hummocks at Ascension.

Lead, separation from silver.

Lesson, M., on craters at Ascension.


Lime, sulphate of, at Ascension.

Lonsdale, Mr., on fossil-corals from Van Diemen's land.

Lot, St. Helena.

Lyell, Mr., on craters of elevation.
-on embedded turtles' eggs.
-on glossy coating to dikes.

Macaulay, Dr., on calcareous casts at Madeira.

MacCulloch, Dr., on an amygdaloid.
-on chlorophaeite.
-on laminated pitchstone.

Mackenzie, Sir G., on cavernous lava-streams.
-on glossy coatings to dikes.
-on obsidian streams.
-on stratification in Iceland.

Madeira, calcareous casts at.

"Magazine, Nautical," account of volcanic phenomena in the Atlantic.


Mauritius, crater of elevation of.

Mica, in rounded nodules.
-origin in metamorphic slate.
-radiating form of.

Miller, Prof., on ejected Labrador feldspar.
-on quartz crystals in obsidian beds.

Mitchell, Sir T., on bombs.
-on the Australian valleys.

Mud streams at the Galapagos archipelago.

Narborough island.

Nelson, Lieut., on the Bermuda islands.

New Caledonia.

New Red sandstone, cross cleavage of.

New South Wales.

New Zealand.

Nulliporae (fossil), resembling concretions.

Obsidian, absent at the Galapagos archipelago.
-bombs of.
-composition and origin of.
-crystals of feldspar sink in.
-its irruption from lofty craters.
-passage of beds into.
-specific gravity of.
-streams of.

Olivine decomposed at St. Jago.
-at Van Diemen's land.
-in the lavas at the Galapagos archipelago.

Oolitic structure of recent calcareous beds at St. Helena.


Oysters, extinction of.

Panza islands, laminated trachyte of.

Pattinson, Mr., on the separation of lead and silver.

Paul's, St., rocks of.



Peron, M., on calcareous rocks of Australia.

Phonolite, hills of.
-with more fusible hornblende.

-dikes of.

Plants, extinct.

Plutonic rocks, separation of constituent parts of, by gravity.

Porto Praya.

Prevost, M. C., on rarity of great dislocations in volcanic islands.

Prosperous hill, St. Helena.

Pumice, absent at the Galapagos archipelago.

Puy de Dome, trachyte of.

Quail island, St. Jago.

Quartz, crystals of, in beds alternating with obsidian.
-crystallised in sandstone.
-fusibility of.
-rock, mottled from metamorphic action with earthy matter.

Red hill.

Resin-like altered scoriae.

Rio de Janeiro, gneiss of.

Robert, M., on strata of Iceland.

Rogers, Professor, on curved lines of elevation.

Salses, compared with tuff craters.

Salt deposited by the sea.
-in volcanic strata.
-lakes of, in craters.

Sandstone of Brazil.
-of the Cape of Good Hope.
-platforms of, in New South Wales.

Schorl, radiating.

Scrope, Mr. P., on laminated trachyte.
-on obsidian.
-on separation of trachyte and basalt.
-on silex in trachyte.
-on sphaerulites.

Seale, Mr., geognosy of St. Helena.
-on dikes.
-on embedded birds' bones.

Seale, on extinct shells of St. Helena.

Sedgwick, Professor, on concretions.

Septaria, in concretions in tuff.

Serpulae on upraised rocks.


Shells, colour of, affected by light.
-from Van Diemen's land.
-land, extinct, at St. Helena.
-particles of, drifted by the wind at St. Helena.

Shelly matter deposited by the waves.

Siau, M., on ripples.

Signal Post Hill.

Silica, deposited by steam.
-large proportion of, in obsidian.
-specific gravity of.

Siliceous sinter.

Smith, Dr. A., on junction of granite and clay-slate.

Spallanzani on decomposed trachyte.

Specific gravity of recent calcareous rocks and of limestone.
-of lavas.

Sphaerulites in glass and in silicified wood.
-in obsidian.

Sowerby, Mr. G.B., on fossil-shells from Van Diemen's land.
-from St. Jago.
-land-shells from St. Helena.

St. Helena.
-crater of elevation of.

St. Jago, crater of elevation of.
-effects of calcareous matter on lava.

St. Paul's rocks.

Stokes, Mr., collections of sphaerulites and of obsidians.

Stony-top, Little.

Stratification of sandstone in New South Wales.

Streams of obsidian.

Stutchbury, Mr., on marine remains at Otaheite.

Subsided space at Ascension.


Talus, stratified, within tuff craters.


Tertiary deposit of St. Jago.

Trachyte, absent at the Galapagos archipelago.
-at Ascension.
-at Terceira.
-decomposition of, by steam.
-its lamination.
-its separation from basalt.
-softened at Ascension.
-specific gravity of.
-with singular veins.

Trap-dikes in the plutonic series.
-at King George's sound.

Travertin at Van Diemen's land.

Tropic-bird, now rare, at St. Helena.

Tuff, craters of.
-their breached state.
-peculiar kind of.

Turner, Mr., on the separation of molten metals.

Tyerman and Bennett on marine remains at Huaheine.

Valleys, gorge-like, at St. Helena.
-in New South Wales.
-in St. Jago.

Van Diemen's land.

Veins in trachyte.
-of jasper.

Vincent, Bory St., on bombs.

Volcanic bombs.
-island in process of formation in the Atlantic.
-islands, their distribution.

Wacke, its passage into lava.

Wackes, argillaceous.

Webster, Dr., on a basin-formed island.
-on gypsum at Ascension.

White, Martin, on soundings.

Wind, effects of, on the form of craters.

Charles Darwin

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