230 
Transactions of the Boijal Society of South Africa. 
but that I prefer rather to confine myself to those branches with which I 
have myself been more directly concerned. 
The year 1882 saw the first introduction of astronomical photography 
^nto the Cape Observatory. No special appliances for the purpose were 
at the time included in its equipment, but the unexpected appearance of 
the great comet of that year demanded that an effort should be made to 
secure a representation of this comet by photographic methods w^hich had 
been vigorously developed elsewhere for such purposes. Accordingly the 
services of a local photographer were secured, and in order to obtain a 
sufiBciently long exposure to bring out the faint detail of the comet's tail, 
his camera was attached to one of the equatorial telescopes of the Observa- 
tory so that it might partake of the motion imparted to the telescope and 
thus be kept pointed on the comet for a prolonged interval. 
Valuable photographs showing much detail of the structure of the 
comet were obtained, but the feature to which particular attention was 
directed w^as the large number of stars, some of them extremely faint 
which, besides the comet, were all duly recorded on the plate. Moreover,, 
the sharpness of the photographic images suggested that they would 
permit of very accurate measurement, and that, if only similar definition 
could be obtained in photographs on a more open scale, it might be 
possible to replace many of the laborious methods of measurement 
hitherto conducted by direct visual observations on the sky itself by 
somewhat similar methods applied to the photographs. 
There existed at the time no comprehensive survey of the Southern 
skies. A complete catalogue of the stars in the Northern heavens known 
as the Bonn " Durchmusterung," giving the positions and magnitudes 
of all stars down to the 9th visual magnitude with a precision at least 
accurate enough to ensure their identification in the sky, had been formed 
by Argelander and extended to a portion of the Southern Hemisphere by 
his successor Schonfeld, but the remainder of the heavens from 23° S. 
Declination to the South Pole was still comparatively unknown. The 
photographs I have above referred to suggested a means by which this 
lacuna might be filled, and no sooner was this idea conceived by Sir 
David Gill than steps were taken to put it into active execution. Partly 
at his own personal expense and partly by means of assistance from the 
Government Grant Fund administered by the Eoyal Society of London, 
the necessary equipment and the services of a photographer were secured, 
and between the years 1885-89 a complete series of photographs of the 
region extending from 18° S. Declination to the South Pole was obtained. 
In order, however, that these photographs might be of value to science, 
it was necessary that the facts duly recorded on them should be minutely 
examined and rendered accessible to astronomers generally in the form of 
a catalogue. As more than 400,000 stars were involved, this in itself was^ 
