II.—FERNANDO NORONHA; TERCEIRA; TAHITI, ETC.

FERNANDO NORONHA.—Precipitous hill of phonolite.

TERCEIRA.—Trachytic rocks: their singular decomposition by steam of high temperature.

TAHITI.—Passage from wacke into trap; singular volcanic rock with the vesicles half-filled with mesotype.

MAURITIUS.—Proofs of its recent elevation.—Structure of its more ancient mountains; similarity with St. Jago.

ST. PAUL’S ROCKS.—Not of volcanic origin.—Their singular mineralogical composition.