of Edinburgh, Session 1884 - 85 . 
193 
object at once, or never (for longer looking merely fatigues the eye, 
and at last deprives it of all power) — the photographic dry-plate 
goes on accumulating the effects of an at first invisible star, until by 
such accumulation a visible, or rather developable, mark is at length 
made ; and if 5 minutes are not enough to produce that effect, a 
\ hour, J hour, or even a whole hour may be tried. 
To compass such an interval, the clock-work movement of any 
equatorial must of course be particularly good, and sedulously 
watched to keep the star-images always on one spot, and prevent 
their being drawn out into ellipses. But this correction being 
applied, then the only chemical operation left with the astronomer, 
is the developing of the latent image on the plate ; which operation, 
however, may be delayed with these new plates to next day, or 
week, or month even, if agreeable. 
Now the special examples of this new stellar photography which 
I have to lay before the meeting, — have been kindly sent to me by 
my friend Dr David Gill, Astronomer-Royal at the Cape of Good 
Hope : and as he is not present here, but is now on the other side 
of the world, I need have no compunction about alluding to him as 
a new rising star, of the first magnitude and richest promise, appear- 
ing just now above the Astronomical horizon; and by his singular 
genius, and surpassing success in whatever he undertakes, doing as 
much honour to his native city, the Granite Queen of the North, as 
to the Tercentenary of the Edinburgh University, where he received 
an Honorary Degree last year. 
A professional photographer, with abundant supplies of apparatus 
and materials, was recently sent out to him, to act under his direc- 
tions ; and he has now accordingly begun, with that aid, the regular 
and systematic mapping of the whole Southern Sidereal heavens, 
seven degrees by seven degrees at a time ; and the examples he has 
just sent, are merely the first essays. Yet they possess already a 
very considerable degree of perfection; and are specially to be com- 
mended for the neatness and roundness of all their stellar discs, — 
the long exposures notwithstanding. 
The 1st of these interesting photographs represents, in chief, the 
three notable stars forming the belt of Orion, on a scale of 1 inch to 
1 degree, and with an exposure of half an hour. 
The 2nd represents the same subject, but with an exposure of one 
