X THE STARRY HEAVENS 391 



times the most brilliant star. Yet, like all 

 the other planets, she glows only with the 

 reflected light of the Sun, and consequently 

 passes through phases like those of the Moon, 

 though we cannot see them with the naked 

 eye. To Venus also owe we mainly the power 

 of determining the distance, and consequently 

 the magnitude, of the Sun. 



THE EARTH 



Our own Earth has formed the subject of 

 previous chapters. I will now, therefore, only 

 call attention to her movements, in which, of 

 course, though unconsciously, we participate. 

 In the first place, the Earth revolves on her 

 axis in 24 hours. Her circumference at the 

 tropics is 24,000 miles. Hence a person at the 

 tropics is moving in this respect at the rate of 

 1000 miles an hour, or over 16 miles a 

 minute. 



But more than this, astronomers have 

 ascertained that the whole solar system is 

 engaged in a great voyage through space, 

 moving towards a point on the constellation 



