-each insect working its utmost from the hour of its birth until
that of its death.

There are various kinds of coral insects, which form varied species of
coral rock. Some kinds of coral assume the form of rounded masses; some
are like a branching shrub; others are in layers, or thin plates; and
some are shaped like the human brain, from which they derive their
name--brainstones. These different kinds differ also in colour, and
thus present a beautiful appearance when seen at the bottom of clear and
shallow water.

In regard to the rate at which the corallines build their cells there is
some diversity of opinion--some asserting that the process is
imperceptible, while others state as positively that it is rapid. There
can be no doubt that some localities and positions are more favourable
to the growth of coral than others. Dr Allan, while at Madagascar,
made several experiments to test this. He selected several masses of
coral, each weighing about ten pounds, and of different species. These
he placed three feet below the surface of the sea, and staked them in to
prevent removal. In a little more than six months they were found to
have risen nearly to the surface, and to have attached themselves to the
solid rock.

There is also a case mentioned of a ship in the Persian Gulf which, in
the course of twenty months, had her copper encased with living coral to
the thickness of two feet.

On the other hand, it is asserted, and we doubt not with equal truth,
that many reefs do not seem to increase in size in the course of many
years.

When a coral reef has reached the surface, the formation of an island
instantly begins; but it necessarily takes a long time ere this island
becomes habitable by man. Among the first plants that raise their heads
to the sea-breeze is the graceful cocoa-nut palm. This tree is
exceedingly hardy, and is found growing on reefs which are so low that
at a distance the trees seem to be standing on the surface of the water.
Indeed many of them spring out of the pure white sand, and their roots
are washed perpetually by the salt spray. Nevertheless, the fruit of
such trees is sweet and good.

Coral islands of the kind we have just described seldom rise more than a
few feet above the level of the sea; but most of them are clothed with
luxuriant vegetation.

We might easily fill a volume on the subject of the ocean's inhabitants,
small and great; but we think the few to which we have mad