54 LIGHT SCIENCE FOR LEISURE HOURS. 



are poor because of the action of the same process of 

 aggregation which has attracted within the Nubeculse 

 a larger share than usual of stellar and nebular glories ? l 

 It need hardly be mentioned that the former argu- 

 ment, on which the distinction between the Nubeculse 

 and other celestial objects has been founded, is disposed 

 of at once if we recognise the stellar and nebular 

 systems as in reality forming but a single scheme. Not 

 only so, but the Nubeculse afford a striking argument 

 in favour of the latter view. To return to the somewhat 

 homely illustration made use of above. Our conceptions 

 of the original association between the stones and the 

 gravel arranged in the manner indicated would certainly 

 be strengthened, or would even be changed into abso- 

 lute certainty, if we perceived in a part of the ground 

 two heaps in which stones and gravel were intermixed. 

 When I add that there are two distinctly marked 

 nebular streams leading towards the Nubeculse, as well 

 as several well-marked star-streams tending in the 

 same direction, the evidence of association seems greatly 

 strengthened. 



If these views be accepted, we shall have to look upon 

 the world of stars as made up of all classes of clustering 

 aggregations, besides strange wisps and sprays extend- 

 ing throughout space in the most fantastic convolutions. 

 Then also, while dismissing the idea that the nebulae as 



1 Sir William Herschel has recorded a peculiarity respecting nebulae 

 which is worthy of mention in connection with the facts above consi- 

 dered. ' I have found,' he says, ' that the spaces preceding nebulse were 

 generally quite deprived of stars, so as often to afford many fields 

 without a single star.' 



