These last are nothing more than narrow circles of land surrounding a smooth lagoon, connected by a single opening with the sea.

Some of the lagoons, said to have subterranean outlets, have no visible ones; the inclosing island, in such cases, being a complete zone of emerald.

Other lagoons still, are girdled by numbers of small, green islets, very near to each other.
The origin of the entire group is generally ascribed to the coral insect.
According to some naturalists, this wonderful little creature, commencing its erections at the bottom of the sea, after the lapse of centuries, carries them up to the surface, where its labours cease.
Here, the inequalities of the coral collect all floating bodies; forming, after a time, a soil, in which the seeds carried thither by birds germinate, and cover the whole with vegetation.

Here and there, all over this archipelago, numberless naked, detached coral formations are seen, just emerging, as it were from the ocean.

These would appear to be islands in the very process of creation--at any rate, one involuntarily concludes so, on beholding them.
As far as I know, there are but few bread-fruit trees in any part of the Pomotu group.