96 



PERIODIC COMETS. 



und the sun in an oval orbit, and that the time of its revolution was about six 

 ears and eight months. It has since returned at its predicted times ; and has 

 >een adopted as a member of our system, under the name of Biela's comet. 



The annexed diagram, fig. 2, exhibits the form and position of the orbit of this 

 omet in relation to those of the principal planets, giving the successive posi- 

 ons it assumed during its appearance in 1832. 



Fig. 2. 



Biela's comet moves in an orbit whose plane is nearly the same with those 

 of the planets. It is but slightly oval, the length being to the breadth in the 

 proportion of about three to two. When nearest to the sun, its distance is 

 nearly equal to that of the earth ; and when most remote from the sun, its dis- 

 tance soiyewhat exceeds that of Jupiter. Thus it ranges through the solar 

 system, between the orbits of Jupiter and the earth. 



Notwithstanding the discovery of the periodic comets of Encke and Biela, 

 still the comet of Halley maintains a paramount astronomical interest, and may 

 be considered to stand alone in exhibiting those physical phenomena which 

 seem to be the exclusive characteristics of the class to which it belongs. Al- 

 though the cornets of Encke and Biela are unquestionably objects of interest to 

 the geometer and astronomer, yet their short periods, the limited space within 



