Flinders
and Bass
1798.
This cove is the highest part of the Derwent to which a ship can advance. There is no danger in proceeding thus far, except off Shoal Point, about two miles below, on the western shore; and on the opposite side, near the echoing cliffs, there are 12 to 17 fathoms. Above Risdon Cove the mud flats commence, and will stop any vessel which draws more than ten or twelve feet; although there be, in some places higher up, from 5 to 8 fathoms. Mount Direction, on the north side of Risdon Cove, forms two round heads which are distinguishable from the entrance of the river, bearing N. 16° W. from Cape Direction. The latitude observed under the mount, from the moon's meridian altitude, was 42° 48′ 12″ south; variation of the azimuth compass on the south side of the cove, 8° 28′, and of the surveying theodolite 9° 15′ east; but I found it alter one or two degrees in different places, both in Norfolk Bay and in the Derwent, owing to partial attractions in the land.[1]
In Risdon Cove the tide rises between four and five feet, which is more, by at least a foot, than it appeared to be at the entrance of the river. The time of high water is about eight hours after the moon's passage over the meridian, or one hour later than in Adventure Bay.[2] In the narrow parts, above Sullivan Cove, the tides run with tolerable regularity, and with some degree of strength; but towards the entrance of the river, the water at the surface sometimes ran down twelve hours together, and at other times as much upwards, whilst the rise and fall by the shore were at the usual periods. These anomalies were probably occasioned by the wind, and seemed not to extend far below the surface; for I found a counter current at the bottom.
The banks of the Derwent are not remarkably high, but the country in general may be termed mountainous. Mount Table, at the back of Sullivan Cove, is supposed to be three-quarters of a mile in height; nor do I think, from having seen it beyond the distance- ↑ Upon the top of Mount Table, the compass has since been found to vary as much as 20°, from one part of the mountain to another.
- ↑ See Bligh's Voyage to the South Seas; page 58.
