The mean dip of the south end of the needle at Cattle Point was 62 deg. 52’

Variation of the compass, observed by lieutenant Flinders on Garden Island in the following year, 8 deg. 51’ east.

No remarks were made at this time upon the tide; but it is known to be high water in Port Jackson about eight hours and a quarter after the moon’s passage over and under the meridian; and the usual rise to be between four and six or seven feet.  When high water takes place between three or four in the afternoon and one or two in the morning, it rises from six to eighteen inches higher than the preceding flood; and the following ebb descends a few inches lower than that which preceded the high tide.

The range of the thermometer on board the ship, was from 51 deg. to 69 deg.; and nearly the same on shore.  The mercury in the barometer stood from 29.60 to 30.36 inches; but it was remarkable that it stood lowest in the fine weather, when the wind came from the westward off the land, and was highest in the rainy, squally weather, with the wind from the sea.  According to the information communicated by colonel W. Paterson, F. R. S., commander of the troops at Port Jackson, this relation between the mercury and the weather was general here in the winter season, when the eastern winds bring rain with them; and I had frequent occasion to remark upon the South Coast, that sea winds raised the mercury in the barometer, whilst those from the land, even with fine weather, caused it to descend.

CHAPTER XI

Of the winds and currents on the south coast of Terra Australis, and in Bass’ Strait.  Usual progress of the gales.  Proper seasons for sailing eastward, and for going westward:  best places of shelter in each case, with some instructions for the Strait.

[SOUTH COAST. WINDS AND CURRENTS]

Before entering upon the second part of the voyage, it seems proper to give an account of the winds and currents which prevailed upon the South Coast; and to add thereto such other general information as may be useful in rendering the navigation more safe and expeditious, both along the coast and through Bass’ Strait.

The rate and direction of the currents here described, are deduced from the daily positions of the ship by astronomical observation, compared with those given by a log kept in the common way, but with somewhat more than common attention.  In the observations, however, there may be some errors, and a log cannot be depended upon nearer than to five miles in the distance, and half a point in the course for the twenty-four hours; and consequently this account of the currents must be taken as subject to the sum, or to the difference of the errors in the observations and log; though it is probable they may have been diminished by taking the medium of several days, which has always been done where it was possible.