CLUSTERS OF STABS. 193 



and testifies to the admirable illuminating power of 

 the refractor of that Observatory which has an object-glass 

 fifteen inches in diameter ; since even a reflector with a 

 specumm of eighteen inches in diameter did not reveal "a 

 trace of the presence of a star." 77 Although it is probable 

 that the cluster in Andromeda was, at thf; close of the tenth 

 century, already recorded as a nebula of oval form, it is more 

 certain that Simon Marius (Mayer of Guntzenhausen), the 

 same who first observed the change of colour in scintillation, 7 * 

 perceived it on the 15th of December, 1612 ; and that he was 

 the first who described it circumstantially, as a new starless 

 and wonderful cosmical body, unknown to Tycho Brahe. Half 

 a century later, Boulliaud, the author of Astronomia philolaica, 

 occupied himself with the same subject. This cluster of star* 

 which is 2j in length and more than 1 in breadth, is spe- 

 cially distinguished by two remarkable very narrow black 

 streaks, parallel to each other, and to the longer axis of the 

 cluster, which, according to Bond's investigations, traverse the 

 whole length like fissures. This configuration vividly reminds 

 us of the singular longitudinal fissure, in an unresolved ne- 

 bula of the southern hemisphere, No. 3501, which has been 

 described and figured by Sir John Herschel. ( Observations at 

 the Cape, pp. 20, 105, pi. iv. fig. 2.) 



Notwithstanding the important discoveries for which we 

 are indebted to Lord Rosse and his colossal telescope, I 

 have not included the great nebula in Orion's belt in thk 

 selection of remarkable clusters of stars, as it appeared to me 

 more appropriate to consider those portions of it which have 

 been resolved, in the section on Nebula). 



The greatest accumulation of clusters of stars, although by 

 no means of nebulae, occurs in the Milky Way, 79 (Galaxias, 



77 Outlines, 874, p. 601. 



8 Delambre, Hist. d?. I'Astr. moderne. t. i. p. 697. 

 79 We are indebted for the first and only complete descriptiou 

 VOL. in. o 



