IV.—ST. HELENA.

Lavas of the feldspathic, basaltic, and submarine series.—Section of Flagstaff Hill and of the Barn.—Dikes.—Turk’s Cap and Prosperous Bays.— Basaltic ring.—Central crateriform ridge, with an internal ledge and a parapet.—Cones of phonolite.—Superficial beds of calcareous sandstone.— Extinct land-shells.—Beds of detritus.—Elevation of the land.— Denudation.—Craters of elevation.