34 THE SIDEEEAL UNIVERSE. 



an investigation, is the shapes and apparent relative densities 

 of these starry clusters. By telescopic measurements of rela- 

 tive distances in relative directions, accomplished in the man- 

 ner before illustrated, Sir William Herschel decided that the 

 great cluster, of which our own sun is a member, and of which 

 the greater portion of stars, owing to their immense distances, 

 seem to rest on one general plain, and surround us in the 

 great zone called the " Milky Way," is of an irregular form, 

 approaching that of a circle, but thick in the middle, and thin 

 toward the edges, in one of which there is a horizontal split 

 or opening. Other clusters are of all conceivable forms, but 

 of these forms the round, or oblately spheroidal, most pre- 

 vails. Even in elongated, curved, angular, and branching 

 clusters, there are often apparently several centers of incipi- 

 ent rotundity. Generally these centers are well denned, and 

 toward them the stars, though with an inappreciable motion, 

 are apparently flowing from all directions, becoming thicker 

 and more compressed as they approach, and being thinner, 

 and gradually shading ^>ff into invisibility, at more distant 

 removes. 



The general uniformity in the appearances of these spherical 

 aggregations, and especially of their comparative denseness in 

 the center, which thence gradually and regularly diminishes, 

 in all directions, toward the circumference, shows that their 

 aggregation is governed by some grand law ; and what can 

 this be but the familiar law of Gravitation that identical law 

 which, in the same form of action, is so potent in our own 

 system, giving sphericity to every collection of fluid particles, 

 from those which compose the planet, to those which form the 

 dew-drop 1 It is gratifying to find in those remote creations 

 such distinct indications of a property which is possessed in 

 common with our own system, and which binds the nearest 



