ing off the west
and south side of Piron Island to a distance of seven or eight miles,
with a well defined border towards Coral Haven.

At the western portion of the Louisiade Archipelago the reefs seen by us
exhibit great irregularity of outline, continuity, and width. Some are
linear reefs, others atolls* more or less distinct in character, and the
remainder are usually round or oval. Viewed as a whole they form an
interrupted chain, with numerous deepwater channels, which terminates in
the West Barrier Reef of the chart but is connected with the coast of New
Guinea by a bank of soundings, with, probably, a well-defined margin.
Many low, wooded islands are scattered along this line. I know of no
distinguishing feature presented by the coral reefs of the Louisiade
compared with those which I have seen elsewhere. One remarkable
occurrence, however, connected with them, may be mentioned. While passing
in the ship the most northern point of Rossel Island, I observed upon the
reef, about a hundred yards inside its outer border, a series of enormous
insulated masses of dead coral rising like rocks from the shallow water.
The largest of these, examined through a good telescope from the distance
of half a mile, was about twenty feet in length and twelve in height,
with a well-defined high-water mark. It formed quite a miniature island,
with tufts of herbage growing in the clefts of its rugged sides, and a
little colony of black-naped terns perched upon the top as if incubating.

(*Footnote. "An atoll differs from an encircling barrier reef only in the
absence of land within its central expanse; and a barrier reef differs
from a fringing reef in being placed at a much greater distance from the
land with reference to the probable inclination of its submarine
foundation, and in the presence of a deep water lagoon-like space or moat
within the reef." The Structure and Distribution of Coral Reefs by
Charles Darwin page 146.)

THEORY OF THEIR FORMATION.

I had only once before seen a similar exhibition of such great and
permanently elevated masses of dead coral upon a living reef--a
phenomenon of much interest in connection with Mr. Darwin's theory of the
mode of formation of coral reefs. This was on a portion of the Great
Barrier Reef of Australia, visited in company with Mr. Jukes, who has
published a detailed account of it.* In both cases the only obvious
explanation is that these huge blocks--too massive to have been hove up