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 
