406 THE BEAUTIES OF NATURE CHAP. 



SHOOTING STARS 



On almost any bright night, if we watch a 

 short time some star will suddenly seem to 

 drop from its place, and, after a short plunge, 

 to disappear. This appearance is, however, 

 partly illusory. While true stars are immense 

 bodies at an enormous distance, Shooting Stars 

 are very small, perhaps not larger than a pav- 

 ing stone, and are not visible until they come 

 within the limits of our atmosphere, by the 

 friction with which they are set on fire and 

 dissipated. They are much more numerous on 

 some nights than others. From the 9th to 

 the llth August we pass through one cluster 

 which is known as the Perseids ; and on the 

 13th and 14th November a still greater group 

 called by astronomers the Leonids. The 

 Leonids revolve round the Sun in a period of 

 33 years, and in an elliptic orbit, one focus of 

 which is about at the same distance from the 

 Sun as we are, the other at about that of 

 Uranus. The shoal of stars is enormous ; its 

 diameter cannot be less than 100,000 miles, 

 and its length many hundreds of thousands. 



