We found to our surprise that the group into which we had penetrated was entirely distinct from that under which we had first anchored to the southward, so that we had already discovered the Abrolhos to form three separate groups.

RAT ISLAND.

The centre island we named Rat Island, from the quantity of that vermin with which it was infested.  We also saw here a few seals, and numbers of a very pretty lizard (figured in the appendix) with its tail covered with spines.  Several of these were brought away alive.  I had two myself for nine months on board, and afterwards presented them to Lady Gipps.  Of those taken by Lieutenant Emery, he was so fortunate as to bring one alive to England, in 1841.  It is still in his possession, and thrives remarkably well.  In one of his last letters he writes to me as follows on the subject:  “The Abrolhos lizard is very docile, and knows Mrs. Emery quite well, and will eat and drink out of her hand; but is timid with strangers.  Its habits are rather torpid, but it becomes active when in the sun or before the fire.  It eats so very little that a piece of sponge cake about the size of a small bean will satisfy it for three or four weeks.  It changes its skin twice a year.”

The formation of Rat Island resembles that already noticed in Pelsart Group; there were the same low overhanging cream-coloured limestone cliffs, to the height of half the island; the greatest elevation of which was 13 feet, with a similar soil, mixed with guano, and filled with burrows of the sooty petrel, or mutton bird.  Surrounding it is a low coral reef, trending northward to the outer edge of the group.

CORAL FORMATION.

This reef afforded me an opportunity of examining the coral formation of the Abrolhos, which, with the exception of Bermuda, is the place farthest removed from the equator where coral formation is found.  The reef on which Rat Island rests extends off four hundred yards on the inner side, and has 12 fathoms just off it, on a grey sandy mud.  The greater portion is composed of a variety of corals intermixed, and forming a consolidated mass, with brain-stones scattered over.  It is nearly dry at low-water; but a portion does not rise so high, projecting out so as to form a narrow shelf, from the edge of which a wall descends almost sheer to the depth of 54 feet.  The upper 20 feet are formed of a peculiar kind of coral, growing in the shape of huge fans, spreading out from stout stems overlapping each other in clusters, and having angular cavities between.  The coral forming the lower 34 feet of the wall is of the common large branch kind.

Whilst in Good Friday Harbour the quarter-master reported smoke on one of the islands to the north-east.  All eyes were instantly turned in that direction, in curiosity to find what could have caused it.  And sure enough a long streak of smoke was curling upwards through the air.  It soon however appeared that it rose from some fire on the main, distant about thirty-five miles, and that its being visible by us was owing to the extreme clearness of the atmosphere.