Finding the western shore of Cobourg Peninsula placed too far from Port Essington on the chart, it was determined to commence the survey at Popham Bay, choosing for the observation spot a small bank of sand and dead coral lying in its centre, and bearing East 1/2 South 1/4 of a mile from where we anchored in nine fathoms. We named this Bird Island, from finding it almost covered with terns and gulls. The latitude of it according to our observations was 11 degrees 15 1/2 minutes South and longitude West of Port Essington 22 1/2 miles, being 4 1/2 less than is given in Captain King's chart, the North-West extreme of the Peninsula being there placed too far from Port Essington, and the North-East point, Cape Croker, too near, it would appear that the discrepancy was chiefly in the position of Port Essington, with respect to the northern extremes of the Peninsula, as Captain King and ourselves only now differ two miles in the distance between Cape Croker and Popham Bay, ours being the greater. The evening was calm as usual, while midnight brought with it a fresh South-East wind. During the night the temperature was as low as 73 degrees. July 25. On leaving at daylight we crossed over to examine the western shores of Dundas Strait, formed by the eastern side of Melville Island; Captain King having passed it in the night. As we stood close along it into the gulf, we found the soundings very irregular. Six miles North 40 degrees East from Cape Keith, we passed over two patches of only three or four fathoms; these we could not see from the general disturbed and discoloured state of the water, it blowing fresh from South-East. We found the nature of this part of Melville Island to be low rocky points, separating sandy bays. One of the few remarkable features on it, is a round hill 320 feet high, five miles North-West from Cape Keith. CLARENCE STRAIT. Passing the latter, we crossed over to the opposite eastern entrance point of Clarence Strait, Cape Hotham, discovering on our way thither a reef nearly awash, about two miles in extent, bearing South 25 degrees West fifteen miles from Cape Keith, and North 10 degrees East fourteen miles from Cape Hotham. The deepest water we found while crossing was 22 fathoms, five miles north of the latter, the general depth being 13 and 15 fathoms. The wind failing in the afternoon, it was evening when we reached our anchorage in nine fathoms, Cape Hotham bearing South 43 West, two miles and a half, and close to the edge of a large shoal which we subsequently found to extend a mile and a half north, and six miles east from the Cape. Here we found the tides set West by South and East-North-East from half a knot to two knots, the westerly stream beginning nearly three hours after high-water, a peculiarity generally occurring in straits. July 26.