CHAPTER XXXIX. 

 THE PLANETS AND ASTEROIDS. 

 MERCURY. 



INCLUDING our own globe there are eight principal planets viz., Mercury, 

 Venus, Mars, Jupiter, Saturn, Uranus, and Neptune. The two first-named 

 being between us and the sun, are termed interior planets ; the others are 

 exterior. Mercury, Venus, and Mars are smaller than Earth. The other four 

 are much larger. 



We have already described the planets as bodies wandering through 

 the zodiac, and reflecting the sun's light. Their orbits are very different 



F 'g- 576. An Orrery- 



from the moon's ; for instance, planets take a retrograde motion as well as 

 a direct one. The sun and the planets revolving around him constitute the 

 solar system. 



We will commence our brief consideration of them with Mercury, the 

 planet nearest to the sun. 



The distance of Mercury from the sun is 35,000,000 of miles, less than 

 half the distance our earth is from him, and so receives much more heat and 

 light than we do. The sun to the Mercurians, if there be any inhabitants 



