396 SPECIAL RESULTS IN THE URANQLOG1CAL 



planets according to the hypothesis of Olbers ; and whether 

 this original large comet may not have been separated into 

 several parts by the influence of Mars ; such a separation, or 

 bi-partition, having actually taken place almost before the 

 eyes of observers, in the year 1846, on the last return of 

 the interior comet of Biela. Certain resemblances between 

 the elements have led Professor Stephen Alexander, of the 

 College of New Jersey, to undertake investigations respect- 

 ing Ihe possibility of a common origin of the asteroids, (or 

 small planets between Mars and Jupiter,) and some, or even 

 all, of the comets ( 646 ) . On grounds of analogy founded on the 

 supposed nebulous envelopes of the small planets, all recent 

 and more accurate observations show that the hypothesis is 

 quite unsupported. Other circumstances are also un- 

 favourable to it. Although it is true that the orbits of the 

 small planets are not parallel to each other, and present, 

 indeed, in the case of Pallas, the phenomenon of an ex- 

 cessive inclination, yet with all this want of parallelism in 

 their own paths, they do not, like comets, intersect the 

 orbits of the great, old, or longer known planets. This 

 circumstance, which, in any hypothesis of a primitive 

 impulse in direction and velocity is exceedingly material, 

 taken in conjunction with the diversity in physical constitu- 

 tion between the interior comets and the small planets, 

 the planets appearing to be entirely without any nebulous 

 or vaporous matter, seems to render a similarity of origin 

 between these two classes of cosmical bodies very improba- 

 ble. Laplace, also, in his theory of "planetary genesis" 

 from zones of vapour revolving around the sun and con- 

 densing round nuclei, thought that comets must be separated 

 entirely from planets. "Dans Fhypothese des zones de 



