32 A CENTURY'S PROGRESS IN ASTRONOMY. 



Herschel believed many to be connected with 

 the sidereal system ; considering that in some 

 parts of the Galaxy " the stars are now drawing 

 towards various secondary centres, and will in 

 time separate into different clusters." He was 

 coming to the view that the star-clusters were 

 secondary aggregations within the Galaxy, prob- 

 ably the true theory. He pointed out that in 

 Scorpio, the cluster Messier 80 is bounded by 

 a black chasm, four degrees wide, from which 

 he believed the stars had been drawn in the 

 course of time to form the cluster. His sister 

 records that one night, after a "long, awful 

 silence," he exclaimed on coming on this chasm 

 "Hier ist wahrhaftig ein Loch im Himmel!" 

 (Here, truly, is a hole in the heavens.) 



Herschel was now gradually giving up his 

 theory of external galaxies and his " disc-theory " 

 of the Universe ; but he still believed even the 

 nebulous objects to be irresolvable only through 

 immensity of distance. In 1791, however, he 

 drew attention to a remarkable star in Taurus, 

 surrounded by a nebulous atmosphere, regarding 

 which he wrote, "View, for instance, the nine- 

 teenth cluster of my sixth class, and afterwards 

 cast your eye on this cloudy star. Our judg- 

 ment, I will venture to say, will be that the 

 nebulosity about the star is not of a starry 



