OF ARTS AND SCIENCES, 297 



consequence of its being discovered by that astronomer to 

 move in an elliptical orbit of five years and a half period. 

 To the objection made against this theory, that it had not 

 before been seen, Lexell replied, that it might be a new comet, 

 drawn into an elliptical orbit by the action of Jupiter, and that 

 it would approach that planet again in 1779, which might 

 then, perhaps, throw it off from our system, to return no 

 more. In point of fact, astronomers have looked in vain for 

 the return of Lexell's comet ! 



In the month of November, 1843, M, Faye saw a comet, 

 whose observed movement could not be reduced to a parabolic 

 curve. Dr. Goldschmidt discovered that it described an el- 

 lipse of a period of seven years and a half. The objection 

 to this theory, that it ought to have been seen before, was 

 answered, as in the case of Lexell's comet, by reference to the 

 action of Jupiter. 



As the region of the heavens where this approach to Jupiter 

 took place was nearly the same for both comets, M. Leverrier 

 was led to admit the possibility, that the comets of 1770 and 

 1843 might be the same, although their orbits were altogether 

 different. 



In 1844, M. de Vico, at Rome, discovered a comet, which 

 was shown by M. Faye to move in an orbit of five years and 

 a half. The possibility that this was Lexell's comet of course 

 conflicted with M. Leverrier's first impressions, just men- 

 tioned, but increased the probability that Lexell's comet might 

 be recovered in one or the other of the recent discoveries. 



" The only difficulty," says M. Leverrier, " was, that the calcula- 

 tions became immensely laborious, and I was obliged to devote to them 

 several years, including the last (1846). Although my researches are 

 brought to a close, however great my desire to submit them to the 

 Academy, the necessity of passing some days in collecting the docu- 

 ments relative to the comet of De Vico will oblige me to confine my- 

 self at present to that of M. Faye."- 



The elements of the comet of 1770, being different from 



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