THE PLANETS, ARE THEY INHABITED \ 



two concentric rings placed one within the other. This conjec- 

 ture was converted . into certainty by the discovery that the 

 same dark streak is seen in the same position on both sides of 

 the ring. It has even been affirmed by some observers that 

 stars have been seen in the space between the rings ; but this 

 requires confirmation. It is, however, considered as proved 

 that the system consists of two concentric rings of unequal 

 breadth, one placed outside the other, without any mutual 

 contact. 



5. While the planet is carried round the sun in its orbital 

 motion, the rings are presented to the view of observers situate 

 on the earth under different aspects. In two positions of the 

 planet at opposite points of its orbit the ring is seen edgeways, 

 its plane then passing through the earth. It assumes these 

 positions at intervals of about fifteen terrestrial years, or half a 

 Saturnian year. If the ring were thick enough to be distinctly 

 visible, and if its thickness were uniform, it would at these times 

 have the appearance represented in fig. 1. 



Fig. 1. 



As it moves from these positions the rings become inclined 

 at a sensible angle to the visual line, and this angle increasing 



Fig. 2. 



from year to year, they appear more and more open, as repre- 

 sented in fig. 2 ; until, after an interval of 7 years, or a quarter 



