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.
