COMETS. 115 



ing the nature and uses of the ring there have been various 

 hypotheses. Dr. Herschel thinks it not less solid than the 

 body of Saturn itself, and it is observed to cast a strong 

 shadow upon it. The light of the ring is generally brighter 

 than that of the planet, which has been attributed to its si- 

 tuation above the region of mists and clouds. Both the pla- 

 net and the ring perform their rotations about the same com- 

 mon axis, and in nearly the same time. The ring disappears 

 twice in every revolution of the planet round the sun ; that 

 is, once in fifteen years, and Saturn appears quite circular 

 for nine months together. Some have supposed that the use 

 of the ring is to collect, refract, and transmit the rays of tlig 

 sun to the body of the planets 



The planet Uranus, or Herschel, completes a revolution 

 round the sun in about eighty-four years. On account of 

 its distance from the earth, which is eighteen hundred mil- 

 lions of miles, its diurnal rotation has never been determined. 

 Heat and light at Uranus are about three hundred and sixty 

 times less than at the earth. It is scarcely visible to the 

 naked eye, although its diameter is thirty-five thousand miles. 

 Astronomers formerly considered it as a star, but on the 13th 

 of March, 1781, Dr. Herschel discovered it to be a planet. 



Qltestions. — 1. How far is Saturn from the sun? 2. What de- 

 gree of light and heat has it ? 3. How often does it revolve round the 

 sun ? 4. On its ov/n axis ? 5. What is the appearance of Saturn as 

 seen through a telescope ? 6. Describe the ring. 7. What is said con- 

 cerning the nature and uses of the ring. 8. In what time does Ura- 

 nus complete a revolution ? 9. At what distance from the sun .'' 10. 

 What is the diameter of Uranus ? 11. Degree of heat and light ? 12^. 

 When and by whom discovered.-' [Note. Saturn's inner ring is dis- 

 tant from its body 21,100 miles. The breadth of the inner ring is 

 20,000 miles. The outer ring is distant from the inner ring 2,839 

 miles, and the breadth of the outer ring is 7,200 miles. Uranus is the 

 name which has been given to the planet Herschel, or Georgium Si- 

 dus, on the continent of Europe.} 



LESSON 53. 



Comets. 



Hast thou ne'er seen the comet's flaming flight ? 

 Th' illustrious stranger passing, terror sheds 



