H. A. Newton — The Story of Biela? s Comet. 



89 



ber 1 of other years, and the Biela comets, all belonged to each 

 other. 



It is then properly a part of my story to show you the 

 behavior of one of the streams of meteoroids. Standing several 

 hundreds of miles away, see them enter the upper atmosphere. 

 They are entirely unseen until they strike the air. They then 



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come down like drops of fiery rain a few miles, in parallel lines, 

 burning up long before they reach the ground (see fig. 9). 

 The air is in fact a shield, protecting the men below from a 

 furious bombardment. The region of the luminous tracks is 

 many miles above that of the highest mountains. 



Go farther away. Parallel lines may show the paths of the 

 meteoroids, though the bodies io. 



themselves are too small to be 

 seen. They strike a little way 

 into the air, to some persons 

 coming from the zenith, to 

 some coming obliquely, to 

 some skimming through, the 

 upper air — and unseen i>y all 

 upon one whole hemisphere. 

 I need hardly remind you 

 that sunlight, and twilight, 

 and clouds often come in to 

 prevent the seeing of the star- 

 flights by persons below. 



Go still farther away. From outside look in toward the sun 

 upon the earth and meteoroid stream. The meteoroids in fact 

 are not to be seen. The stream is of unknown depth, perhaps 

 millions of miles deep. Its density increases in general toward 

 the center. We cross the densest part of the November stream 

 in two or three hours, and the whole of it in 10 or 15 hours, 

 while the passage of the August stream requires three or four 

 days. The Biela stream is crossed obliquely, the meteoroids 

 overtaking the earth. The August stream is nearly perpendic- 

 ular, and the November stream meets the earth. 



Again go still farther away, out to the point from which we 

 first looked down upon the earth and comet. We then see (by 



