18 THE SKY. 



most beautiful appearance through a good telescope, its vast 

 size causing it to look larger than those which are much 

 nearer; it has several shadowy belts across it, which are 

 supposed to be openings in the strata of clouds which 

 surround it, drawn into ring-like forms by the rotation of 

 the planet, these are shown in fig. 18. It being probable 



FIG. 18. 



that this great planet is surrounded by strata of the densest 

 clouds which only open in the tropical region, its inhabitants 

 therefore, (if there be any) get but a glimpse of the firmanent 

 and its stars through them, in those situations at or near 

 to the planet's equator. These dense clouds serve a very 

 useful purpose in regions so very far removed from the 

 source of heat, for if radiation were permitted to go on 

 freely from the surface of the planet the sun's rays would 

 be too feeble to compensate for it, and the cold would be 

 intense ; but the clouds reflect back the heat radiated from 

 the surface and keep in what little heat is received at that 

 great distance. Jupiter has four satellites or moons, which 

 revolve round it as our moon does round this earth. 



Far beyond Jupiter rolls another stupendous orb called 

 Saturn, not so large as Jupiter, but still immense, being 

 847 times the bulk of the earth. It is placed at the distance 

 of 906 millions of miles from the sun. An idea of this 

 may be formed from the fact that light, which travels 



