A HISTORY OF SCIENCE 



of meteors came whizzing into our atmosphere in lieu 

 of the lost comet. 



And so at last the full secret was out. The awe- 

 inspiring comet, instead of being the planetary body 

 it had all along been regarded, is really nothing more 

 nor less than a great aggregation of meteoric particles, 

 which have become clustered together out in space 

 somewhere, and which by jostling one another or 

 through electrical action become luminous. So widely 

 are the individual particles separated that the cometary 

 body as a whole has been estimated to be thousands of 

 times less dense than the earth's atmosphere at sea- 

 level. Hence the ease with which the comet may be 

 dismembered and its particles strung out into stream- 

 ing swarms. 



So thickly is the space we traverse strewn with this 

 cometary dust that the earth sweeps up, according to 

 Professor Newcomb's estimate, a million tons of it each 

 day. Each individual particle, perhaps no larger than 

 a millet seed, becomes a shooting-star, or meteor, as it 

 burns to vapor in the earth's upper atmosphere. And 

 if one tiny planet sweeps up such masses of this cosmic 

 matter, the amount of it in the entire stretch of our sys- 

 tem must be beyond all estimate. What a story it tells 

 of the myriads of cometary victims that have fallen 

 prey to the sun since first he stretched his planetary net 

 across the heavens! 



THE FIXED STARS 



When Biela's comet gave the inhabitants of the earth 

 such a fright in 1832, it really did not come within 

 fifty millions of miles of us. Even the great comet 



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