On the west there are very few, Wamma and Palo Pabi being the chief, with Ougia, and Wassia at the north-west extremity.

On the east side the sea is everywhere shallow, and full of coral; and it is here that the pearl-shells are found which form one of the chief staples of Aru trade.
All the islands are covered with a dense and very lofty forest.
The physical features here described are of peculiar interest, and, as far as I am aware, are to some extent unique; for I have been unable to find any other record of an island of the size of Aru crossed by channels which exactly resemble true rivers.

How these channels originated were a complete puzzle to me, till, after a long consideration of the whole of the natural phenomena presented by these islands, I arrived at a conclusion which I will now endeavour to explain.

There are three ways in which we may conceive islands which are not volcanic to have been formed, or to have been reduced to their present condition, by elevation, by subsidence, or by separation from a continent or larger island.

The existence of coral rock, or of raised beaches far inland, indicates recent elevation; lagoon coral-islands, and such as have barrier or encircling reefs, have suffered subsidence; while our own islands, whose productions are entirely those of the adjacent continent, have been separated from it.