184 LIGHT SCIENCE FOR LEISURE HOURS. 



ceived. Just as Halley s comet, when close to the sun, 

 sweeps rapidly round him that is, in a sharply curved 

 path so the new comet s path was sharply bent around 

 the temporary focus formed by the great planet. But 

 just as Halley s comet, after perihelion passage, moves 

 away from the sun, so Lexell s comet, after what may 

 be termed perijovian passage, moved away from Jupi 

 ter, and passed again within the sun s attraction. From 

 this time the comet began to follow a new orbit around 

 the sun. This new orbit was an oval of moderate 

 eccentricity, round which the comet travelled in about 

 five and a half years. 



At the next return of the comet to perihelion, it was 

 not likely that astronomers would obtain a view of it ; 

 for, on account of the odd half-year in its period, it 

 came to perihelion when the earth held a point in her 

 orbit exactly opposite to that which she had occupied 

 at the comet s former perihelion passage ; therefore, 

 the comet, which before was favourably, was now un 

 favourably situated for observation. 



As the period for the comet s second return ap 

 proached, astronomers looked out eagerly for its advent. 

 Again and again the heavens were swept for the 

 faint speck of nebulous light which should have an 

 nounced the return of the wanderer. But days, and 

 weeks, and months passed, until it became certain 

 that either the comet had been shorn of nearly all its 

 former brilliancy, and had thus escaped unnoticed, or 

 that something had happened to deflect it from its 

 course. 



