works of others, the principal kinds of coral-reefs, more especially those
occurring in the open ocean, and to explain the origin of their peculiar
forms. I do not here treat of the polypifers, which construct these vast
works, except so far as relates to their distribution, and to the
conditions favourable to their vigorous growth. Without any distinct
intention to classify coral-reefs, most voyagers have spoken of them under
the following heads: "lagoon-islands," or "atolls," "barrier" or
"encircling reefs," and "fringing" or "shore-reefs." The lagoon-islands
have received much the most attention; and it is not surprising, for every
one must be struck with astonishment, when he first beholds one of these
vast rings of coral-rock, often many leagues in diameter, here and there
surmounted by a low verdant island with dazzling white shores, bathed on
the outside by the foaming breakers of the ocean, and on the inside
surrounding a calm expanse of water, which from reflection, is of a bright
but pale green colour. The naturalist will feel this astonishment more
deeply after having examined the soft and almost gelatinous bodies of these
apparently insignificant creatures, and when he knows that the solid reef
increases only on the outer edge, which day and night is lashed by the
breakers of an ocean never at rest. Well did Francois Pyrard de Laval, in
the year 1605, exclaim, "C'est une merueille de voir chacun de ces
atollons, enuironne d'un grand banc de pierre tout autour, n'y ayant point
d'artifice humain." The accompanying sketch of Whitsunday island, in the
South Pacific, taken from Captain Beechey's admirable "Voyage," although
excellent of its kind, gives but a faint idea of the singular aspect of one
of these lagoon-islands.

(PLATE: UNTITLED WOODCUT, WHITSUNDAY ATOLL.)

Whitsunday Island is of small size, and the whole circle has been converted
into land, which is a comparatively rare circumstance. As the reef of a