THE PLANETS. 15 



What does it give to the earth? 



In what respect does the light of the moon differ from that 

 of the sun ? 



What season is relieved by the influence of the moon ? 

 What alterations in form does the moon undergo ? 

 What does all this lead us to admire ? 

 What do you understand by the solar system ? 

 How many of the heavenly bodies move round the sun ? 

 What are they called ] 

 W r hat is a planet 1 

 What are primary planets 7 

 What are secondary planets ? 

 What other names are given to them ? 

 What determines the length of the days in the planets ? 



LESSON III. 



THE PLANETS COMETS THE FIXED STARS. 



THERE are eleven primary planets, named Mer- 

 cury, Venus, the Earth, Mars, Vesta, Juno, Ceres, 

 Pallas, Jupiter, Saturn, and Uranus, which is also 

 called the Georgium Sidus. 



Mercury, the nearest to the sun, being distant 

 from it thirty-four millions of miles, is 3,200 miles 

 in diameter, and performs its journey round the 

 sun in about eighty-eight days, moving in a single 

 second nearly thirty of our miles. 



Venus is 7,700 miles in diameter, and revolves 



round the sun in 224 days 16 hours, at the distance 



of nearly sixty-nine millions of miles. This is the 



Brightest of all the planets, and is sometimes to be 



een in the day-time with the naked eye. It is 



