SATURN'S MOONS AND BELTS 179 



hang to the disk a long while before they would 



vanish Tho seventh ! innermoK 



minutes, and the sixth 



.. II -.'.' :.-.. : 



10 moons would have been at once hid behind 



; 1 takes place when a star comes up t-- 



and vanishes behin ho star is seen to 



t at once; and tho conclusion drawn is that this 



o.ul.l not happen unless there were no atmosphere or 



n iu tho moon to keep the star in ni^ht 



for us ally vanished Our atmos] 



gives us twilight, in. inmj an<i evening, and enables 



us to see tho sun some minutes before ho rises, and 



for as long after ho has set Ultimately Herschel 



perceived a quintuple belt, two dark an<l thr. )-i 



times also he noticed a whitish li^ht 



ut tho poles similar to the polar spots on Mars, and 



he believed, to the same cause. But what these 



re is a problem still unsolved The vast 



body of Saturn is lighter than the same volume of 



water, and would float in it like cork. Our ear: 



about ii\ times heavier than a globe of water of the 



same size, and would sink in water like lead Whether 



Saturn ia still a heated mass, slowly cooling down, and 



these clouds arise from streams of gas given off, remain 



lems for 



With improved mirrors and a less powerful 

 scope, he watched tho movements and changes of the 

 Between 1790 and 1806 ho wrote seven papers 

 Koyal Soci< ' --.it urn and his system. 



v he came to the conclusion, which he dismissed 

 t a- improbable, that tho ring was not singl* 

 double, with a #ulf t \\vnty-ti\v hundred miles [1680] in 



