392 THE BEAUTIES OE NATURE chap. 



of Hercules at the rate of at least 20,000 

 miles an hour, or over 300 miles a minute.^ 



But even more again, we revolve annually 

 round the Sun in a mighty orbit 580,000,000 

 miles in circumference. In this respect we 

 are moving at the rate of no less than 60,000 

 miles an hour, or 1000 miles a minute — a 

 rate far exceeding of course, in fact by some 

 100 times, that of a cannon ball. 



How few of us know, how little we any of 

 us realise, that we are rushing through space 

 with such enormous velocity. 



MARS 



To the naked eye Mars appears like a 

 ruddy star of the first magnitude. It has 

 two satellites, which have been happily named 

 Phobos and Deimos — Fear and Dismay. It 

 is little more than half as large as the Earth, 

 and, though generally far more distant, it 

 sometimes approaches us within 35,000,000 

 miles. This has enabled us to study its 

 physical structure. It seems very probable 



1 Some authorities estimate it even higher. 



