self, on revisiting it in April, 1843, concur to show that it has diminished to 28° 58′.
The perfection to which the making of chronometers has attained has rendered general magnetic charts almost unnecessary for nautical purposes; but there are some meridians where the change of variation is so rapid, that in cases where chronometers cannot be depended upon, or are altogether wanting, the longitude may be determined with a considerable degree of exactness by such means; especially to the southward of Australasia, on the usual track of all vessels going from England to her colonies, as also on the meridian of the Cape of Good Hope, and is well worthy the attention of those in charge of our merchant ships.
Aug. 10.The 10th was a beautiful moderate day, and afforded us an opportunity, during the afternoon, of trying the temperature of the ocean in various parts, to the depth of six hundred fathoms, but without striking ground. At 10 h. 50 m. p.m. a burr was observed round the moon, the inner circle being 0° 53′, and the outer 1° 50′ distant from her disc, exhibiting brilliant prismatic colours.
Aug. 12.At noon the south-west cape of New Holland was observed, bearing N.E. by N., distant nine or ten leagues, and some other parts of the coast soon afterwards became visible. But just at this time the wind increased so suddenly and violently, that we could hardly take in our sails quickly enough, and in a few minutes were reduced to a close-reefed main-topsail: at 8 p.m., when blowing