62 JOURNAL AND PROCEEDINGS 
ing the process of manufacture explained by the world-famed 
optician who figured it. To give some idea of the difficulty in- 
volved in producing a dise of glass 28 inches in diameter per- 
fectly homogeneous and without any flaw or blemishes whatso- 
ever, Sir Howard Grubb said he had to diseard no less than 
eighteen pieces of glass, all specially prepared for him, before he 
selected the one whose optical qualities were considered good 
enough for him to retain and grind into the lens which now rests 
in the National Observatory of Great Britain. The important 
instruments used in the transit room for determining time at the 
prime meridian were marvels of accuracy and skill. Mention 
was also made of the astrographic twin telescope, the 30 inch re- 
flector, and the 26 inch and 9 inch Thompson photographie re- 
fractors—everyone superb instruments—while the whole routine 
work was carried on by a staff of about sixty experts. 
During the period Sir Robert Ball was Astronomer Royal of 
Ireland, Mr. Jenkins received an invitation to visit Dunsink 
Observatory, near Dublin, and those who were acquainted with 
that delightful book, ‘‘The Story of the Heavens,’’ were familiar 
with the building and its outfit. The principal telescope there - 
was 12 inches aperture, the lenses of which were presented to the 
Board of Trinity College, Dublin, by Sir James South, and the 
telescope was known as the South Equatorial. The Observatory 
also contained a very good 6 inch Transit instrument by Repsold. 
The transits of the celestial bodies over the meridian of Dunsink 
‘were recorded by electrical contact on a chronograph, and a pho- 
tograph of the latter instrument given to Mr. Jenkins as a sou- 
venir was exhibited. 
Two Observatories were located in the ancient city of Oxford, 
and visits to both were described. The Radcliffe Observatory 
contained many fine instruments, while the University Observa- 
tory was one of the institutions engaged in the International 
Photographic Survey of the Heavens, which was without doubt 
the most gigantic astronomical work of modern times. In the 
year 1887 a congress of astronomers was held in Paris, and they 
decided to prepare a photographie chart of the whole sky, which 
