ANNIVERSARY ADDRESS. 19 
been cloudy and unfavourable, so much so that only one night in 
five has been fine enough for photography, and many of these only 
fine for one or two hours. By securing photographs upon every 
available night, four hundred and seventy have been obtained. 
The star camera has been almost confined to the catalogue plates 
of part of the survey of the whole heavens ; but in December an 
important experiment was made, it was shown that a photograph 
of a comet with surrounding stars can be taken in five (5) minutes 
and thus is secured a permanent record of the comet’s position 
with reference to surrounding stars, which can be measured with 
extreme accuracy. In this way the comet’s position is determined 
from each star with as much accuracy as it could be by the old 
method in an hour, even when large telescopes are used. One 
photograph, then, taken in five minutes will fix the comet’s place 
with as much accuracy as can be attained by many hours’ work 
with a large telescope ; this is obviously an important adaptation 
of photography, for the saving of time, and for the possibility it 
affords of fixing a comet’s position in cloudy weather. 
One remarkable cluster of stars, 3315 in Herschel’s list, has 
been subjected to a searching examination with the star camera 
to see if any nebulous matter could be found amongst the stars, 
but none has been found by long exposures of eight hours, and 
with the most sensitive plates we have ever used. The stars stand 
outlined on a background of space. Herschel called this object 
“a, glorious cluster of immense magnitude, the most brilliant 
object of the kind I have ever seen ; there are at least two hundred 
stars in it.” But its magnificence when photographed under the 
searching power of the large star camera may be judged from the 
_ fact that the camera records more than ten times as many stars 
as Herschel said. Meridian observations and double star work 
have also been carried out during the year, and a number of new 
double stars discovered. 
Meteorology.—The daily weather charts published at the Obser- 
vatory for four and a half years, have been submitted to careful 
examination, and some very important facts brought to light. 
