ghly improbable, the survey of the Rattlesnake
having completed all that was requisite for the immediate purposes of
navigation in those parts.

GEOLOGICAL REMARKS.

The fact of the existence of several active volcanoes on islands
immediately adjacent to the north coast of New Guinea (first made known
by Dampier) and the circumstance of volcanic bands traversing the length
of many of the great islands of the Malayan Archipelago, and others as
far to the southward as New Caledonia and New Zealand, rendered it
extremely probable that we should have found indisputable signs of
comparatively recent volcanic action in the south-east part of New
Guinea. We saw no volcanoes, however, and the great central mountain
chain appeared to me to be probably granitic. The large Brumer Island is
composed of igneous rocks as formerly mentioned; and at Dufaure Island I
obtained from some canoes which came off to us a few smooth water-worn
pieces of hornblendic porphyry. Some specimens of obsidian, or volcanic
glass, were also procured from the natives at the latter place, where
sharp-edged fragments are used for shaving with; one variety is black,
another of a light reddish-brown, with dark streaks. Mount Astrolabe is
apparently of trap formation, as I have already stated. Some conical
hills scattered along the coast may possibly be of volcanic origin,
especially one of that form rising to the height of 645 feet from the
lowland behind Redscar Head. It is in this neighbourhood also that we
find the upraised calcareous rocks of modern date exhibited by the
Pariwara Islands and the neighbouring headland, with which they were
probably once continuous; near this, too, the barrier reef of the coast
ceases at Low Island, which it encloses, although its line is continued
under water, as a ridge of coral, as far as the South-west Cape, where
the coral ends, unless the shoals apparently blocking up the channel
south of Yule Island are of the same formation.

LOUISIADE ARCHIPELAGO.

Reference to the outline chart will enable the reader to follow me in
some general remarks which did not properly enter into the narrative. The
Louisiade Archipelago, reduced to what I conceive to be its natural
limits, includes that extensive group of islands comprised between the
parallels of 10 degrees 40 minutes and 11 degrees 40 minutes South
latitude, and the meridians of 151 degrees and 154 degrees 30 minutes
East longitude. About eighty are already known, an