RECENT CONGLOMERATE.
On the shores of Quail Island, I found fragments of brick, bolts of iron, pebbles, and large fragments of basalt, united by a scanty base of impure calcareous matter into a firm conglomerate. To show how exceedingly firm this recent conglomerate is, I may mention, that I endeavoured with a heavy geological hammer to knock out a thick bolt of iron, which was embedded a little above low-water mark, but was quite unable to succeed.
CHAPTER 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.