yet seen, we found that the outer
edge consisted of a wall higher than any of the parts within, rising at
low-water, to an elevation of ten feet, while inside, pools or holes
existed, three or four feet deep, containing live coral, sponges,
sea-eggs, and trepang. Scattered about on different parts of the reef
were many Chama gigas, not, however, so large as those I had formerly
seen at Keeling or Cocos Islands, in the Indian Ocean, weighing 220
pounds.

Singular to say, at 3 P.M., I observed the latitude by a meridian
altitude of Venus, although a bright sunny day. The result agreed with
Captain King's chart, placing the centre of the island in latitude 11
degrees 28 minutes South.

TIDAL OBSERVATIONS.

We experienced more tide here than at any anchorage we had yet occupied
during the passage. From 1 to 5 P.M., it set half an knot an hour to the
southward, then changed to North-West by North, increasing its rate to
one knot by 10 o'clock, and decreasing it to a quarter of a knot by 2
A.M., when it again set to the South-South-West. The stream thus appears
to set nine hours North-West by North and three South-South-West. The
short duration of the latter, which is the ebb, is caused by the
northerly direction of the prevailing current. This also was the only
spot where our fishermen had any success; in a few hours several dozen of
a species of small red bream being caught.

Three or four ships passing together would find a secure berth about two
miles North-North-East of where the Beagle anchored, where the depth is
moderate, with good holding ground. It has great advantage in this
particular over Cairncross, where but one vessel could lie snug, and
still greater over Turtle Island, more exposed even than the former with
a strong tide, and where vessels ride very uneasily. Moreover the
supposed Boydan, or Number 1 isle, can be left a full hour before
daylight, there being nothing in the way to impede a ship's progress for
some miles. Those who are not desirous of passing the reefs off Wednesday
and Hammond Islands, late in the day, with the sun in an unfavourable
position, can find a convenient stopping place in Blackwood Bay under the
largest York isle, or under the Cape of that name.

CAIRNCROSS ISLAND.

July 12.

We left at an early hour, steering North-North-West 1/2 West for
Cairncross Island, which we passed at a distance of half a mile from the
eastern side in 16 fathoms. Its height is seventy-five feet to