CHAPTER XV. 



A FALLING STAR. 



EVERY one who has occasionally taken a nocturnal walk 

 in the open country will probably have seen what is called 

 " a shooting star." Perhaps I might rather say that 

 unless the observer be very inattentive he will have 

 noticed dozens, or scores, or hundreds of these objects, 

 either bright or faint, with long streaks or with short. 



For the due exhibition of a shooting star, that part of 

 the sky where it is displayed should, of course, be free 

 from cloud, and the silvery streak will seem all the more 

 vivid if the moon be absent. No telescope is needed. 

 This is, indeed, tne one branch of astronomical observation 

 in which the unaided eye can advantageously dispense 

 with optical assistance. 



Our present knowledge as to the natural history of the 

 shooting stars has been mainly acquired during the last 

 hundred years. The first important step in the compre- 

 hension of these bodies was to recognise that the brilliant 

 flash of light was caused by some object which came from 

 without and plunged into our air. This was known at 



