THE SIDEREAL UNIVERSE. 721 



CHAPTER IV. 



COMETS. 



Among the myriads of stars scattered through the vault 

 of heaven, there are none which have so much taxed the 

 imagination of the learned as comets. They have often 

 given rise to the most opposite and most ridiculous hypoth- 

 eses. Descartes thought they were only old stars which 

 had become crusted over and sick, and which, being too 

 feeble to maintain their places, were borne away by the 

 vortices of neighboring stars. 



The regular movements of comets seem to have been 

 suspected by Seneca, but it was Newton who taught the 

 method of calculating them. These vagabond stars, how- 

 ever, frequently move in such a way as to deceive all the 

 sagacity of astronomers. The reader may recollect, in ref- 

 erence to this point, that Jacopo Bernouilli had announced 

 the return of the comet of 1680 for the 17th of May, 1719 ; 

 it ought, at this time, to have made a majestic entry into 

 the sign of the Balance. Voltaire says that in order to see 

 this beautiful spectacle not a single astronomer went to bed 

 that night ; but the comet did not appear. These wander- 

 ing meteors are sometimes guilty nowadays of the same 

 want of politeness. 1 



1 Seneca suspected not only the regular movements of comets, but even the 

 possibility of tracing their path by means of calculation. " I look upon them," 

 he says, " not as wandering fires, but as works that are eternal in their nature. 

 Every comet has its defined limits." See Just. Astron. de Lemonnier. To New- 

 ton belongs the honor of having first demonstrated their course by calculation. 



