COMETS. 535 



major axis of whose orbits for the most part resembles those 

 of the small planets, the question was raised as to whether 

 the group of interior comets may not, as is conjectured by 

 Olbers, in his hypothesis respecting the small planets, 

 originally have formed a single cosmical body ; whether the 

 large comet may not have been separated into several by the 

 influence of Mars, in the same way that such a separation, as it 

 were a bipartition, took place under the eye of the observer 

 in the year 1846, on the occasion of the last return of the 

 interior comet of Biela. Certain similarities in their elements 

 have induced Professor Stephen Alexander, of the College of 

 New Jersey, to institute investigations 2 as to the possibility 

 of a common origin of the asteroids between Mars and 

 Jupiter, with some or even all of the comets. The grounds 

 of analogy which have been deduced from the nebulous 

 envelopes of the asteroids must, according to all more recent 

 and accurate observations, be renounced. The orbits of the 

 small planets are not parallel to each other ; that of Pallas 



2 Stephen Alexander, " On the Similarity of arrangement 

 of the Asteroids and the Comets of short period, and the 

 possibility of their common origin," in Gould's Astronom. 

 Journal, no. 19, p. 147, and no. 20, p. 181. The author 

 distinguishes, with Hind, (Schum. Asir. Nadir. No. 724), 

 " the comets of short period, whose semi-axes are all nearly 

 the same with those of the small planets between Mars and 

 Jupiter ; and the other class, including the comets whose 

 mean distance or semi-axis is somewhat less than that of 

 Uranus." He concludes the first essay with this remark : 

 " Different facts and coincidences agree in indicating a near 

 appulse if not an actual collision of Mars with a large comet 

 in 1315 or 1316, that the comet was thereby broken into 

 three parts, whose orbits (it may be presumed) received even 

 then their present form; viz. that still presented by the 

 omets of 1812, 1815 and 1846, which are fragments of the 

 dissevered comet." 



