KNOWLEDGE. 



observatories which 

 shared the work. Of these 

 Greenwich was one, and 

 an instrnment of the 

 standard pattern — the 

 Astrographic Telescope — 

 was erected at the Obser- 

 \'ator\-. With this instru- 

 ment the share of Green- 

 wich in the great wcirk 

 has been completed, and 

 it is now helping Oxford 

 University Observatorx- in 

 the Oxford share of tin 

 wcnk. In the section ot 

 tJie International Chart 

 and Stars Catalogue 

 allotted to Greenwich, 

 the positions of ncarh- 

 180,000 stars have been 

 measured in duplicate, 

 and about 05.000 en- 

 larged prints of the 

 Chart jilates have bi^eii 

 made at the rate (if 

 12,000 to 13,000 a year. 



f II 



1 lie biiililiii-j t out. lining; the twenty-eiylu ihlIi ciiiKiturial 

 telescope. 



399 



Nearly 720,000 stars have 

 been counted on these 

 plates. 



It is not unw(irth\' of 

 remark that the tirst im- 

 pulse towards this photo- 

 graphic chart of the skies 

 was received when Sir 

 David Gill at the Cape 

 Observatory successfulh' 

 photographed the Comet 

 of 1882 — a task of great 

 difficulty, for the dry plate 

 was not then in use. 



The Thoni[)son Equa- 

 torial has been devoted 

 assiduously to the photo- 

 graphy of faint satellites, 

 comets and planets. The 

 chief objects of Greenw ich 

 have always been those of 

 computation and of accu- 

 rate obser\-ation rather 

 than of ■■ disco\-er\-." but 

 it is worthy of note 

 that all discoveries of 

 planetary satellites since 

 the seventeenth centur\- 



1 lie tuiiil_\ -light Micli iiiiLitmial tLlc^cupe ; obsiiMiig Willi the ^p<.clru.-5Uul)<-. 



