north-east lies Sala-y-Gomez, a small island of
perfectly bare rocks, only inhabited by sea-fowl, and there the
albatross pays a passing visit. Now he rises again and continues his
flight westwards. Soon he comes to a swarm of insignificant islands
called the Low Archipelago. So we name the islands, but the dark-skinned
natives who by some mysterious fortune have been banished to them call
them Paumotu, or "Island Cloud." A poet could not have conceived a
better name. There lie eighty-five groups of islands, each consisting of
innumerable holms. They are really a cloud of islets, like a nebula or
star mist in the sky, and this swarm is only one among many others
studding all the western part of the Pacific Ocean.

Now the albatross soars round the rocks of the "Island Cloud." He can
see them easily from up above, but it is a harder matter for a vessel to
make its way between the treacherous rocks and reefs. Though they are so
many, the aggregate area amounts to less than four square miles. Almost
all are formed of coral, and most of them are atolls. Reef--building
corals are small animals which extract lime from the water. They
multiply by budding, and every group forms a common clan where living
and dead members rest side by side. Coral animalculae demand for their
existence a firm, hard sea bottom, crystal-clear water, sufficient
nutriment brought to them by waves and currents, and lastly a water
temperature not falling below 68 deg. Therefore they occur only in
tropical seas and near the surface, for the water becomes colder with
the depth. At depths greater than 160 feet they are rare. They die and
increase again and again, and therefore the coral reefs grow in height
and breadth, and only the height of water at ebb tide puts a limit to
their upward growth. The continual surf of the sea and stormy waves
often break off whole blocks of coral limestone, which roll down and
break up into sand. With this all cavities are filled in, and thus the
action of the sea helps to consolidate and strengthen the reef. Other
lime-extracting animalculae and also seaweeds establish themselves on the
reef. In the course of time the waves throw up loose blocks on the top
of the reef, so that parts of it are always above the water-level. When
the water rises during flood-tide, white foaming surf indicates the
position of the reef at a long distance. During the ebb the reef itself
is exposed and the sea is quiet. Between ebb and flood th