52 LIGHT SCIENCE FOR LEISURE HOURS. 



valuable communication to the Royal Astronomical 

 Society from the pen of Mr. Cleveland Abbe, an 

 astronomer who has laboured in the sound school of the 

 Poulkowa Observatory. Having recognised in the 

 peculiar arrangement of stars and nebulae above re- 

 ferred to, an argument that the nebulae lie beyond our 

 system, Mr. Abbe suggests that the Magellanic clouds 

 are two of the nearest of the nebular systems, which 

 thus exhibit larger dimensions than their fellow- 

 schemes. 



The converse of this, which may be termed the positive 

 theory of the Nubeculae, is the hypothesis which may be 

 termed the negative theory. Whatever these objects 

 may be, astronomers have said, they are quite distinct 

 from the sidereal system, nor are the nebulae seen 

 within them to be looked upon as fellows of the other 

 nebulae. For in the Nubeculae we see what we recog- 

 nise nowhere else, the combination namely of clustering 

 groups of stars and freely scattered nebulae. It is the 

 characteristic (still I am quoting the theory) of the 

 sidereal system that where its splendours are greatest 

 nebulae are wanting ; it is the characteristic of nebular 

 aggregation that it withdraws itself in appearance from 

 the neighbourhood of clustering star groups. But in 

 the Magellanic clouds neither of these characteristics is 

 to be recognised ; therefore these objects are distinct 

 from either system. 



Nor has another argument been wanting to indicate 

 the distinction that exists between the Magellanic clouds 

 and the other splendours of the celestial vault. Sir 



