anical
action of the waves to the height of two or three yards above the wall
on the leeward side, and then the whole island to sink down a few
fathoms, the appearances described would then be presented by the
submerged reef. A repetition of such operations, by the alternate
elevation and depression of the same mass (an hypothesis strictly
conformable to analogy), might produce still greater inequality in the
two sides, especially as the violent efflux of the tide has probably a
strong tendency to check the accumulation of the more tender corals on
the leeward reef; while the action of the breakers contributes to raise
the windward barrier."[1129]

Previously to my adverting to the signs above enumerated of a downward
movement in the bed of the ocean, Dr. MacCulloch, Captain Beechey, and
many other writers, had shown that masses of recent coral had been laid
dry at various heights above the sea-level, both in the Red Sea, the
islands of the Pacific, and in the East and West Indies. After
describing thirty-two coral islands in the Pacific, Captain Beechey
mentioned that they were all formed of living coral except one, which,
although of coral formation, was raised about seventy or eighty feet
above the level of the sea, and was encompassed by a reef of living
coral. It is called Elizabeth or Henderson's Island, and is five miles
in length by one in breadth. It has a flat surface, and, on all sides,
except the north, is bounded by perpendicular cliffs about fifty feet
high, composed entirely of dead coral, more or less porous, honey-combed
at the surface, and hardening into a compact calcareous mass, which
possesses the fracture of secondary limestone, and has a species of
millepore interspersed through it. These cliffs are considerably
undermined by the action of the waves, and some of them appear on the
eve of precipitating their superincumbent weight into the sea. Those
which are less injured in this way present no alternate ridges or
indication of the different levels which the sea might have occupied at
different periods; but a smooth surface, as if the island, which has
probably been raised by volcanic agency, had been forced up by one great
subterraneous convulsion.[1130] At the distance of a few hundred yards
from this island, no bottom could be gained with 200 fathoms of line.

[Illustration: Fig. 120.

Elizabeth, or Henderson's Island.]

It will be seen, from the annexed sketch, communicated to me by
Lieute