OF THE COSMOS. CLUSTERS OF STARS. 123 



dance of light of the refracting telescope of that Obser- 

 vatory (which has an object glass of 14 Parisian inches 

 diameter), since even a reflecting telescope, in which the 

 mirror has 1 8 inches diameter, does not shew the faintest 

 trace by which the presence of a star can be divined. ( 243 ) 

 The cluster of stars in Andromeda may perhaps have been 

 known as a nebula of oval form as early as the end of the 

 tenth century ; but it is more certain that on the 1 oth of 

 December,1612, Simon Marius( Mayer of Guntzenhauseu, 

 the same who first remarked the change of colour in 

 scintillation ( 244 ) ), distinguished it as anew and wonderful 

 starless cosmical body which had not been named by Tycho 

 Brahe, and it was he who first gave a detailed description 

 of it. Half a century later, Bouillaud, the author of the 

 Astronomia philolaica, occupied himself with the same 

 subject. This cluster of stars, which is 2J long and 

 above 1 broad, is particularly characterised by two re- 

 markable very narrow black streaks, nearly parallel to each 

 other and to the longer axis of the cluster, and, according 

 to Bond's examination, traversing the whole like fissures. 

 This arrangement reminds us strongly of the remarkable 

 longitudinal fissure in an unresolved nebula of the 

 Southern hemisphere, No. 3501, which has been described 

 and figured by Sir John Herschel. (Cape Observ. pp. 

 20 and 105, PL IY. fig. 2.) 



In this selection of remarkable clusters of stars, I have 

 not included the great nebula in Orion's belt, notwith- 

 standing the important discoveries for which we are in- 

 debted to the Earl of Eosse and his colossal telescope, as 

 I prefer reserving it for the section on Nebula3, although 

 portions have thus been already resolved. 



