392 THE BEAUTIES OF 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 
1Some authorities estimate it even higher. 
