NEBULA. 297 



difference between a nebulous spot unresolvable by the teles- 

 copic powers of that age, and a cluster of stars,* to which the 

 mutual proximity of its numerous small stars, not visible to 

 the naked eye, imparts a nebulous lustre. Notwithstanding 

 the great improvements made in optical instruments, the 

 nebula in Andromeda was considered for nearly two centuries 

 and a half as at its discovery to be wholly devoid of stars, 

 until two years since, the transatlantic observer, George Bond, 

 of Cambridge in Massachusetts, discovered 1,500 small stars 

 within the limits of the nebula. I have not hesitated to 

 class it amongst the stellar clusters, although the nucleus has 

 not hitherto been resolved. 10 



It is probably only to be ascribed to some singular accident 

 that Galileo, who, when the Sidereus Nuntius appeared in 1610, 

 had already made frequent observations of the constellation of 

 Orion, should have subsequently mentioned, in his Saggiatore, 

 no other nebula? in the firmament but those which his own weak 

 optical instruments had resolved into stellar clusters, although 

 he might long before have learnt, through the Mundus 

 Jovialis of the discovery of the starless nebula in Andro- 

 meda. When he speaks of the nebulose del Orione e del 

 Presepe, he understands by the expression merely <f aggre- 

 gations (coacervazioni) of innumerable small stars." 11 He 

 successively delineates under the deceptive designations of 

 nebulosce capitis, cinguli, et ensis Orionis, clusters of stars, 

 in which he exults in having discovered 400 hitherto unob- 

 served stars in a space of 1 or 2 degrees. He never makes 

 any reference to unresolved nebulous matter. Yet how could 



* Germ., Sternhaufen ; French, amas d'etoiles. 



10 Cosmos, vol. iii. p. 192. 



11 " Galilei no to die le Nebulose di Orione nuW altro erano 

 che mucchi e coacervazioni d* innumerabili Stelle" Nelli, 

 Vita di Galilei, vol. i. p. 208. 



