48 LIGHT SCIENCE FOR LEISURE HOURS. 



and the idea is at once precluded that the eye is within 

 the cluster, of whatever nature that cluster may be. 

 Therefore the theory that the sun forms one of a system 

 of stars spread pretty uniformly over a disc-shaped 

 space must be given up; for were it true, the ap- 

 proach to the Milky Way would always be gradual. 



When we add that in the southern skies the Milky 

 Way presents the most fantastic configuration, here 

 expanding into fan-shaped masses, there winding about 

 in a multitude of strange convolutions, here suddenly 

 narrowing into a bright neck or isthmus, there exhi- 

 biting a nearly circular vacancy, it becomes clear that 

 the galaxy cannot have the figure assigned to it by Sir 

 W. Herschel. It must consist of streams and sprays 

 of stars at different distances. Such streams by their 

 fantastic convolutions serve to explain all the pecu- 

 liarities of the galaxy's structure. 



And next, have we any evidence that the nebulae 

 are not really beyond the galaxy, but are mixed up 

 with the sidereal system ? It appears to me that we 

 have. 



Sir William Herschel noticed that there are places 

 where the nebulae are much more densely crowded than 

 elsewhere, and he was disposed to suspect that pre- 

 cisely as the stars by their aggregation form the zone 

 of the Milky Way, so there is a zone of nebulas. But 

 when Sir John Herschel had completed the survey of 

 the heavens it was found that a very different law of 

 distribution made its appearance. Instead of being 

 collected in a zone or band around the heavens, the 



