UP TO 6FT 9IN.
During the latter part of last week some very high tides were experienced at Sydney. The automatic tide-gauge at Fort Denison registered 5ft 9 ½ in on January 3, 6ft 3in on the 4th, and 6ft 9in on the 5th. The last- mentioned reading was the highest tide of which the Sydney Observatory has official
The generating forces (writes Mr. W. E. Raymond, officer-in-charge of the Sydney Observatory) were such as to make for very high spring tides in latitudes close to Sydney. The moon (the principal agent) was full on the
4th at 11.30 p.m., and closest to the earth during this lunar month some 12 minutes later,
when it reached very close to its minimum distance. The sun was also closest to the earth on the 3rd, at 9 p.m. Now, the moon's declination about the time it was full was 27deg. 38 min. north, and the sun's declination 22deg. 50min. south. It therefore happened that the solar wave was almost entirely superimposed on the crest of the anti-lunar wave, and that this wave was travelling in latitudes 27 to 28 deg. south. Sydney was therefore favourably situated to feel the effect of the almost total attraction of the sun and moon on the ocean. Prevailing weather conditions also did their share in increasing the level of the water. The barometer at the time of high tide on the 5th was slightly more than two-tenths below the average, and as one-tenth fall in barometric pressure raises the sea level 1½ in., atmospheric pressure alone was responsible for about, 3in. in
the rise of the tide.
The previous record high-water reading at Sydney was on December 18, 1910, when 6ft 9in was registered, at 9.20 a.m.