ANNIVERSARY ADDRESS. 5 
Turning now from these matters affecting the operations of the 
Society, I wish to speak for a short time upon two scientific 
questions which concern us particularly, owing to local circum- 
stances. Astronomers looked forward to the transit of Venus in 
1874 for a solution of one of the most difficult questions—What 
is the distance of the sun? It was thought by those most 
competent to offer an opinion, that there had been so many 
advances since 1769 in the quality of instruments, in the means 
of determining positions on and dimensions of the earth, and such 
an advantage in the use of photography, that the error in the solar 
parallax would not exceed 0-01 of a second. The result, as we 
all know, did not come up to the expectation. The experience of 
the observers of 1769, which was made the text-book for those of 
1874, proved misleading, and the phenomena observed were so 
unexpected that it was in many cases impossible to tell the times 
of contacts within many seconds. And the photographs from 
which so much had been expected proved a failure, for owing to 
the irregular distortion of the pictures taken with the English 
photoheliograph, it was found impossible to measure them with 
anything like the required accuracy. For a time the idea of using 
the transit of 1882 as another means of finding the solar 
parallax was almost given up, so great was the disappointment 
at the comparative failure of the methods used in 1874; but 
when the first surprise was over and a calm estimate of the 
work of 1874 made, it was found that the English and Aus- 
tralian contact observations gave a better value of the parallax 
than had been obtained before, and there had been a real 
gain as to the parallax, and very much learned about the 
phenomena of the transit which will be of immense value to those 
who observe the next, although it is acknowledged that atmo- 
spheric conditions so largely affect the phenomena that the old 
estimate of possible accuracy must be given up. 
ite 1881 the result of the measurements of the American photos 
graphs was published, and it is said they give a good result. ‘The 
Publication of the result from the American photos., and the 
