The observation spot on Rat Island was on the north-east end, which we placed in latitude 32 degrees 42 minutes 50 seconds South and longitude 1 degree 57 minutes 50 seconds West of Swan River.  Having completed our work in the harbour, we left, for the purpose of securing the requisite material for the north-east part of this group, which we found to be a detached cluster with deep-water between, and to be also similarly separated from the extreme of the group—­a small isle about five feet high, composed of sand and dead coral.  The average depth surrounding the islands was 20 and 23 fathoms, being the same level as that of the great flat or plain on which they rest, and which extends out from the mainland, shelving off at the outer edge of the southern part of the Abrolhos almost precipitously to no bottom with 250 fathoms.  We now proceeded southward, to examine the opening between Easter and Pelsart Groups, and to complete the extremity of the northern part of the latter.

SNAPPER BANK.

On our way we discovered a coral bank of 7 fathoms, a mile and a half long, seven miles East-South-East from the north-east end of Easter Group.  We called it Snapper Bank, from the immense quantity of that fish which we found on it.  In half an hour we caught more than we could cure, so that it became necessary to stop the sport.  This shows what a lucrative trade might be carried on by the people of Swan River with the Mauritius; for the lake on the island of Rottnest affording a large supply of salt, any quantity of fish might easily be caught and cured.  The whole group is abundantly supplied, though nowhere so plentifully as at Snapper Bank.

From near the south-east end of this bank the main was visible from the Beagle’s poop.  Here we anchored for the night in 24 fathoms, and next morning stood out to sea between Easter and Pelsart Groups to ascertain if there were any more reefs to the westward, though the long unbroken swell was almost sufficient to convince us that there were none.

SOUNDINGS BETWEEN THE GROUPS.

In a line between the outer reefs of the two groups the depth was 36 fathoms; a mile and a half further in we had 29; but outside it deepened off suddenly to no bottom with 70, and in two miles and a half to none with 170.  Before returning we tried for bottom with 250; but, as has been already mentioned, without success.  Outside the reef we felt a current setting a mile an hour North-North-West.  In standing in again we passed close round the north-west end of the reef encircling Pelsart Group, in 31 fathoms, and anchored in 17, just without a line of discoloured water, which we found to have 5 fathoms in the outer part, extending across the mouth of the lagoon; the largest island bearing South by West one mile and three-quarters.

GUN ISLAND.  DUTCH REMAINS.

April 24.