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
from deep water into their present position by any storm--reached their
present level by the elevation of the sea bottom on which they were
formed.

(*Footnote. Voyage of H.M.S. Fly by J.B. Jukes volume 1 page 340.)

Before quitting the subject of the coral reefs of the Louisiade I may be
permitted to express my conviction of the perfect manner in which many,
perhaps all of the appearances which they present may be satisfactorily
accounted for by the application of Mr. Darwin's theory. We have only to
presume the whole of the Archipelago to have once formed part of New