PROGRESS OF METEORIC ASTRONOMY 



By W. F. DENNING, F.R.A.S. 



Few departments of astronomy were neglected so long as that 

 dealing with meteors and shooting stars, and no branch has 

 attained so much importance in a comparatively short period. 

 The study of shooting stars in their fugitive flights has opened 

 out a new world in celestial physics and enriched our know- 

 ledge to a degree certainly never contemplated by the pioneers 

 in this field of research. The little falling star which glides 

 silently along the azure and forms but a momentary spark, can 

 tell a wonderful story. Its career is ended, it is true, with its 

 fall, and it will never more grace the brow of night with its 

 glories ; but its track amongst the stars has been recorded, and 

 so we can glean much concerning it. Two observations supply 

 the data for the determination of its real path in the air : the 

 length of its luminous course and its velocity. 



The shooting star is found to have taken fire within our 

 atmosphere, and to have entered it from outside. In fact, the 

 event signifies a collision between a small stony mass and the 

 earth's atmosphere. The former is not formed of a highly 

 combustible material ; but it flies into the air with tremendous 

 speed (10 to 44 miles per second) and the concussion generates 

 sufficient heat to render the object incandescent and to destroy 

 it. Every night, every hour, these meteors may be observed 

 to fall. No part of the firmament is free from their incursions, 

 no season of the year is without them ; they are ceaseless, 

 though variable in their times and numbers. In ancient days 

 shooting stars were regarded as atmospheric in their deriva- 

 tions, and thought to indicate electrical phenomena exhaled 

 from the earth and descending again. No one viewed them 

 as being planetary atoms, cosmical in their origin, positions, 

 behaviour, and speed. Our forefathers never dreamed that 

 they formed the dust of the universe drifted, as it were, into 

 dense clouds revolving in mighty orbits around the sun. They 

 never contemplated that the nocturnal sparks which enliven 



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