342 ADDRESS ON PEESENTING THE GOLD MEDAL OF THE [45 



These works would, in the opinion of your Council, even if they stood 

 alone, amply justify the award of your medal. 



Nearly forty years have elapsed since the Society's medal was awarded 

 to Sir John Herschel for his Catalogue of Nebulae and Clusters of Stars, 

 printed in the Philosophical Transactions for 1833. In his address on that 

 occasion, the Astronomer Royal gave an able sketch of the history of our 

 knowledge of the nebulae up to that time, which makes it quite unnecessary 

 for me to go over the same ground, necessarily much more feebly. I may 

 merely recall that the three catalogues of Sir William Herschel, published 

 in the Philosophical Transactions for 1786, 1789, and 1802, contain the 

 places and descriptions of 2500 nebulas and star-clusters. Sir John Herschel's 

 catalogue contains the results of his observations made at Slough, with 

 his 20-foot reflector, between the years 1825 and 1833. These observations 

 were undertaken for the purpose of reviewing the nebulae and star-clusters 

 discovered by his father. The catalogue comprises 2307 of these objects, 

 about 500 of which are new. 



Not content with having made this survey of the heavens visible in 

 this latitude, Sir John Herschel resolved to undertake a similar survey of 

 the southern heavens; and for this purpose he transported to the Cape of 

 Good Hope the same instrument which he had employed in the northern 

 hemisphere, "so as to give a unity to the results of both portions of the 

 survey, and to render them comparable with each other." 



The observations required in order to carry out this grand plan were 

 made in the years 1834, 1835, 1836, 1837, and 1838, and the fruits of 

 these prolonged labours appeared in 1847, in the magnificent work, Results 

 of Astronomical Observations made at the Cape of Good Hope. The survey 

 included the double-stars of the southern hemisphere, as well as the nebulae 

 and star-clusters. The work contains a catalogue of 1708 of these latter 

 objects, entirely similar in its arrangement and construction to the Catalogue 

 of Northern Nebulae in the Philosophical Transactions for 1833, and reduced 

 to the same epoch (1830), in order to facilitate the union of the two 

 catalogues into one general one. Of these objects 89 are common to the 

 two catalogues, so that the number of distinct nebulae and clusters which 

 they contain is 3926. Both of these works of Sir John Herschel contain 

 engraved representations of some of the most remarkable nebulae, whether 

 of typical or of exceptional form, by means of which future observers may 

 be able to ascertain whether any secular changes are perceptible in them. 



