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spectra. The field is too extensive and the ardent workers too 
numerous for inclusion in this brief statement. I shall, therefore, 
as the representative of the Royal Astronomical Society of England, 
introduce to your notice a selection of thirteen photographs, which 
are copies of some which have been presented to the Society and 
described at the meetings of the Fellows at various times during the 
past’ seven years, and I may be permitted to add, that they represent 
the fullest information we yet possess concerning the objects they 
portray. 
The first (Pl. i.) is a photograph of the stars in the Milky Way 
in Cygnus. When you examine it closely, you will find it is almost 
covered with stars, not one of them visible to the sight without the 
aid of the telescope, many of them invisible even with powerful 
telescopes. ‘This is an area of the sky that would be covered by one 
of your smallest silver coins, held between the finger and thumb, at 
arm’s length, between the eye and the sky; the area of sky covered 
by such a piece would be about equal to what this photograph rep- 
resents. The centre of the photograph is in R..A. 19 h. 45 m., 
decl. N. 35 deg. 30 m., and covers a sky area of about 2 deg. 3 m. 
by 1 deg. 45 m. It has been enlarged from the negative to a scale 
of 26 seconds of arc to 1 millimeter, and was taken with the 
twenty-inch reflector, on August 14, 1887, with an exposure of sixty 
minutes. A photograph comparable with this, was taken by the 
brothers Henry, in Paris, in August, 1885, with the thirteen-inch 
photo-refractor, and was one of the early marvels of celestial pho- 
tography. It showed about 3000 stars on the sky area just described, 
but the photograph taken with my twenty-inch reflector, and now 
exhibited, shows no less than 16,000 stars on the same coincident 
area of the sky. Allowing for difference in aperture between the 
two telescopes, there is still a wide margin in favor of the reflector 
for this kind of work. 
The next photograph (PI. ii.) is known as M. 15, in the constel- 
laioneeeseasus, im ho Aare 25 m...decl. N..rr deg).4n m...-The 
scale is 6 seconds of arc to t millimeter, and the field is 18 minutes 
of arc indiameter. The photograph was taken with the twenty-inch 
reflector, on November 4, 1890, with an exposure of two hours, and 
shows a fine example of a globular cluster, but the written descrip- 
tions of it, from eye observations, do it scant justice, and there are 
no drawings available for comparison. The photograph shows the 
central part of the cluster to be involved in nebulosity, as is also 
