ANNIVERSARY ADDRESS. 45 
value. Had the two Berlin results which were published after 
Professor Harkness’ value, been known it would have been altered 
to 8840 in., which makes the sun’s distance ninety-two and a half 
millions of miles. 
Some sixteen years since Sir William Thompson expressed the 
opinion that meteorological conditions might produce such changes 
in the sea level as would for the time change the direction of the 
earth’s axis by as much as half a second of arc, and at the meet- 
ing of the Royal Society this year, he announced that he had a 
letter from the astronomer at Berlin, telling him that he had 
just received a letter from the party of astronomers which the 
International Geodetic Union had sent, at his suggestion, to 
Honolulu to observe the latitude there for a year, while similar 
observations were being made in Berlin with the object of com- 
parison in order to settle the question whether the direction of 
the earth’s axis did or did not actually change. The letter gave 
the result of the first three months’ work, and announced that the 
latitude had decreased almost one-third of a second, and during 
the same period that of Berlin had increased by one-third of 
a second. Since the two places are nearly opposite each other on 
the earth’s surface, this is the strongest evidence yet brought for- 
ward, that the earth’s axis does oscillate to a small extent, but 
yet quite enough to effect some observations seriously. We are 
gradually learning. Jirst the earth’s surface acts something 
like that of an india-rubber ball, yielding to the changing pressure 
due to the tides, the atmosphere, and the moon, and now it seems 
we must admit that even the direction of its axis of rotation is not 
fixed. A preliminary examination of two years’ work with the 
Sydney transit instrument shows that here also there is a decrease 
in the latitude in spring, and in autumn it increases, and members 
may remember that some time ago I mentioned the fact that 
we had at Sydney a change in the direction of the vertical 
amounting to 6”, due to a rain storm. 
Astronomical Photography.—Since December 1891, the Sydney 
Observatory, in common with other Observatories taking part in 
