A vessel intending to go to Oyster Harbour should anchor off the sandy beach immediately to the eastward of the entrance, that is, between the breakers off the point and the bar, in three fathoms sand, bringing the summit of Green Island, in the harbour, on with the extremity of the bushes of the west point of entrance, and the highest part of Breaksea Island in a line with the outer point of the bay: a boat should then be sent to sound the bar. The mark for the deepest part is when the western summit of some flat-topped land, at the back of Oyster Harbour, is a little open of the rocks off the east side of the entrance.
After the bar is passed, the channel is deepest when the centre of the flat land is kept midway between the points of entrance, avoiding a spit of rocks that projects from the rocky point at the west end of the watering beach. The strongest winds are from the westward, and therefore bower anchors should be placed to the south-west and north-west: warps and the stream cable will be sufficient to secure her from easterly winds, as the hills rise immediately over the vessel on that shore. If the run of water outside the bar should fail, holes may be dug at the edge of the grass, about three feet deep, which will yield a sufficient quantity in two or three days for any vessel that can pass over it.
The flood-tide in the entrance generally ran sixteen hours, and ebbed eight hours. High water at full and change took place at 10 hours 10 minutes at night; but on the bar the rise and fall was very irregular, and a vessel going in should pay great attention to the depth, if her draught is more than ten feet, for it sometimes rises suddenly two feet. The spring-tides take place about the third or fourth day after new or full moon. The variation here is about 7 degrees East. The situation of Seal Island, from Captain Flinders’ observations, is in latitude 35 degrees 4 minutes 55 seconds, and longitude 117 degrees 58 minutes 7 seconds.
A small island was reported in the Sydney Gazette to have been seen in latitude 36 degrees 27 minutes, and longitude 127 degrees 2 minutes East; but as the account says, that Kangaroo Island was seen the same day, which is not less than one hundred and fifty leagues from the above position, it appears too vague to be correct. (See Horsburgh Supp. page 32.)
BLACK PYRAMID, off the north-west end of Van Diemen’s Land, in Bass Strait, is situated about 4 minutes too much to the southward on Captain Flinders’ chart.
BELL’S ROCK. The following account of a rock, seen by Mr. Bell, the Commander of the ship Minerva, on her outward-bound passage to New South Wales, appeared in a Sydney (New South Wales) Gazette, of the 16th of December, 1824.
“On the 14th of November the Minerva very narrowly escaped striking on a rock, in the fairway of the west entrance to Bass Strait, on the south side of King’s Island. Reid’s rocks bearing North six miles, and the Black Pyramid East-South-East: from this situation the danger was about half a mile off (to the southward); but as the water broke only at intervals of three or four minutes, although the swell was very heavy, it is probable there may be sufficient depth of water to carry a ship over it. An indifferent observation made the latitude of the ship at the time 40 degrees 26 minutes.”