The Outer Planets 251 



rings are turned toward 

 us, we see them ; when 

 the edges are turned 

 toward us, the rings 

 disappear. 



The outer ring of 



Saturn is 176,000 miles FIG. 151. Photograph of Saturn with the 

 acrOSS ; the planet itself rin s turned edgewise to the earth. 



has a diameter of 74,000 



miles. The inside of the inner ring is less than 10,000 

 miles from the surface of the planet. Of the three rings, 

 the middle one is much the broadest, having a breadth 

 (not diameter) of 17,000 miles. The thickness of the 

 rings is probably not over 100 miles. They are not con- 

 tinuous sheets, but consist of separate particles, probably 

 meteorites, pursuing their orbits like a swarm of little 

 moons around the planet. What a wonderful sight 

 should we find Saturn with its rings and moons, if we 

 were only on one of them ! 



URANUS 



The planet Uranus was discovered by Sir William 

 Herschel in 1781. He was looking for interesting ob- 

 jects in the sky with a telescope he had himself con- 

 structed. Happening to direct it toward Uranus, he 

 saw at once that this was not a star, for it had some 

 breadth instead of appearing as a mere point of light. 

 For a time he thought it was a peculiar sort of comet. 



Uranus requires 84 years to complete its revolution 

 around the sun. It is about 30,000 miles in diameter and 

 may be seen by a good eye without the aid of a telescope. 



