Index - Page 2

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.