8 
Proceedings of Royal Society of Edinhurgh. [dec. 5 , 
First, one of the assistants has been employed during the last three 
years on a photographic survey of the southern heavens : not a survey 
on the colossal scale recommended by the Paris Conference, hut on 
a more manageable and perhaps more useful scale — a scale sufficient 
for the requirements of the practical astronomer, and containing 
more stars than are contained in the maps of Argelander, which, as 
you know, are the best existing maps of the northern heavens. Each 
photographic picture of the Cape series covers an area of four square 
degrees, and about a half of the work is already done. The places of 
the stars arebeingVeduced and tabulated by microscopic measurement. 
Secondly, the Cape Observatory is engaged in a redetermination 
of the right ascensions of fundamental stars, by means of circle 
observations taken in the prime vertical ; that is, in the great circle 
of the heavens which passes from west to east through the zenith. 
Hitherto right ascensions have been determined mainly by means 
of time observations, and their places are affected by errors due to 
the small irregularities of clocks, but still more by errors arising 
from the impossibility of estimating the one-tenth of a second by 
eye and ear. Under the Cape series of determinations the right 
ascensions of all the stars which do not set between south and west 
will be determined by circle readings with the same degree of 
precision as polar distances are now determined. 
Thirdly, the Cape Observatory, as I learn by a communication 
from its director, has commenced a systematic investigation of the 
parallax of the southern stars. I should like to say something 
about the instrument — a masterpiece of mechanical and optical skill 
— with which these delicate measures are being made. But this 
would be wandering too far from my subject. What I wanted to 
say is, that we are not at the present time, either in Greenwich or 
elsewhere, doing, for the northern half, any one of these three things 
which three of the chief instruments of the Cape Observatory are 
employed in doing for the southern half of the celestial sphere. 
You see there is scope for division of labour in astronomy as in 
other things. It is really not doubtful that, with a proper equip- 
ment, our Observatory could be employed on work such as can only 
be done at a national observatory, under official rules and discipline, 
which should not in the least compete with the work done at the 
National Observatory of Greenwich. With the greatest respect for 
