220 SPECIAL RESULTS IN THE UttANOLOGICAL 



per cornu pellucidum de noctu cernatur." Simon Harms 

 goes on to ask himself whether this singular star may be one 

 which has newly appeared : he declines giving any decided 

 reply to his own question, but is struck by the circumstance 

 that Tycho Brahe, who had enumerated all the stars in the 

 girdle of Andromeda, had not spoken of this "nebulosa." 

 Thus, in the Mundus Jovialis, published in 1614, we find, as 

 I have already remarked ( 366 ), an enunciation of the difference 

 between an unresolvable nebula (unresolvable, that is to say, 

 by the telescopic powers then available), and a " cluster of 

 stars" (German, " Sternhaufen," French, " Amas d'etoiles"), 

 in which the crowding together of many small stars, each of 

 which taken separately would be invisible to the naked eye, 

 causes an appearance of nebulous light. Notwithstanding 

 the great improvement in optical instruments, the nebula in 

 Andromeda continued for almost two centuries and a half 

 to be regarded, as at the time of its discovery, as starless, 

 until, two years ago, George Bond, at the Transatlantic 

 Observatory of Cambridge in the United States, recognised 

 1500 small stars within its limits. Although its nucleus is 

 still unresolved, I have not scrupled to class it among star 

 clusters ( 36 ?). 



We can only attribute to a singular accident the circum- 

 stance that Galileo, who before 1610, when the Sidereus 

 Nuntius appeared, had already occupied himself repeatedly 

 with the constellation of Orion, mentions subsequently in 

 his Saggiatore, when he might have long been acquainted 

 from the Mundus Jovialis with the discovery of the 

 starless nebula in Andromeda, no other nebulae in the 

 heavens than those which even his feeble optical instru- 

 ments resolved into clusters of stars. What he terms the 



