Mr.Schomburgk has described ("Geographical Journal" volume 10 page 246.) a great sandstone formation in Northern Brazil, resting on granite, and resembling to a remarkable degree, in composition and in the external form of the land, this formation of the Cape of Good Hope.The sandstones of the great platforms of Eastern Australia, which also rest on granite, differ in containing more earthy and less siliceous matter.No fossil remains have been discovered in these three vast deposits.Finally, I may add that I did not see any boulders of far-transported rocks at the Cape of Good Hope, or on the eastern and western shores of Australia, or at Van Diemen's Land.In the northern island of New Zealand, I noticed some large blocks of greenstone, but whether their parent rock was far distant, I had no opportunity of determining.
INDEX TO VOLCANIC ISLANDS.
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.
Australia.
Azores.
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.
Bole.
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.
Chlorophaeite.
Clarke, Rev.W., on the Cape of Good Hope.
Clay-slate, its decomposition and junction with granite at the Cape of Good Hope.
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 island.
-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.
