CHAPTERS ON THE STARS. 



15 



dividual stars are so faint that the most powerful instruments scarcely 

 suffice to bring them out. One of the most remarkable clusters in the 

 northern heavens is that of Hercules. To the naked eye it is but a 

 faint and insignificant patch which would be noticed only by a careful 

 observer. But in a large telescope it is seen to be one of the most 

 interesting objects in the heavens. Near the border the individual stars 

 can be readily distinguished. But they grow continually thicker 

 toward the center, where, even in a telescope of two feet aperture, the 



Fig. 7. The Cluster GO Centauri, Photographed by Gill at the Cape Observatory. 



observer can see only a patch of light, which is, however, as he scans it, 

 suggestive of the countless stars that must there be collected. By the 

 aid of photography, Professor Pickering has nearly succeeded in the 

 complete resolution of this cluster. 



In many cases the central portions of these objects are so condensed 

 that they cannot be visually resolved into their separate stars, even 

 with the most powerful telescopes. . A closer approach to complete 

 resolution has been made by photography. We present copies of sev- 

 eral photographs which have been made by Pickering, Gill and others. 



