STELLAR CLUSTERS. 



nomers the nature of these objects, which, when examined by 

 sufficient magnifying powers, prove to be masses of stars clustered 

 together in a manner identical with that cluster in which our sun 

 is placed. They appear as they do, mere specks of whitish light, 

 because of their enormous distance. 



78. These objects are not dispersed fortuitously and indifferently 

 on all parts of the heavens. They are wholly absent from some 

 regions, in some rarely found, and crowded in amazing profusion 

 in others. Their disposition, however, is not like that of the stars 

 in general, determined by a great circle of the sphere and its 

 poles. It was supposed that they showed a tendency to crowd 

 towards a zone at right angles to the galactic circle, but a careful 

 comparison of their position does not confirm this. According to 

 Sir W. and Sir J. Herschel, the nebuloe prevail most around the 

 following parts of the celestial sphere : 



1 The North Galactic Pole. 5 Canes Venatici. 



2 Leo major. 6 Coma Berenici. 



3 Leo minor. 7 Bootes (precedingly). 



4 Ursa major. 8 Virgo (head, wings, and shoulder). 



The parts of the heavens, on the other hand, where they are found 

 in the smallest numbers, are, 



1 Aries. 7 Draco. 



2 Taurus. 8 Hercules. 



3 Orion (head and shoulders). 9 Serpentarius (northern part). 



4 Auriga. 10 Serpens (tail). 



5 Perseus. 11 Aquila (tail). 



6 Camelopardus. 12 Lyra. 



In the southern hemisphere their distribution is more uniform. 



79. "What those objects are, and of what they severally consist, 

 admits of no reasonable doubt.; So far as relates to the stellar 

 clusters, their constituent parts are visible. They are, as their 

 name imports, masses of stars collected together at certain points 

 in the regions of space which stretch beyond the limits of our own 

 cluster, and are by distance so reduced in their visual magnitude, 

 that an entire cluster will appear to the naked eye, if it be visible 

 at all, as a single star, and when seen with the telescope will be 

 included within the limit of a single field of view. 



Different clusters exhibit their component stars seen with the 

 same magnifying power more or less distinctly. Thus, for 

 example, fig. 11 represents the appearance of a cluster seen with 

 a powerful telescope, in which the stars appear like grains of 

 silver powder. 



In fig. 12, on the other hand, the component stars are distinct, 

 and those of fig. 13 still more so. 



c 2 ID 



