THE NEW PLANETS. 



Dr. Olbers called this planet PALLAS. 



8. This circumstance, combined with the exceptional minute- 

 ness of these two planets, suggested to Olbers the startling, and 

 then, as it must have appeared, extravagantly improbable hypo- 

 thesis, that a single planet of the ordinary magnitude existed 

 formerly at the distance indicated by Bode's analogy, that it 

 was broken into small fragments either by internal explosion from 

 some cause analogous to volcanic action, or by collision with a 

 comet, that Ceres and Pallas were two of its fragments, and in 

 fine, that it was very likely that many other fragments, smaller 

 still, were revolving in similar orbits, many of which might 

 reward the labour of future observers who might direct their 

 attention to these regions of the firmament. 



In support of this curious conjecture, it was urged that in the 

 case of such a catastrophe as was involved in the supposition, the 

 fragments, according to the established laws of physics, would 

 necessarily continue to revolve in orbits, not differing much in 

 their mean distances from that of the original planet ; that the 

 obliquities of the orbits to each other and to that of the original 

 planet might be subject to a wider limit ; that the eccentricities 

 might also have exceptional magnitudes ; and, finally, that such 

 bodies might be expected to have magnitudes so indefinitely 

 minute as to be out of all analogy or comparison, not only with 

 the other primary planets, but even with the smallest of the 

 secondary ones. 



Ceres and Pallas were both so small as to elude all attempts 

 to estimate their diameters, real or apparent. They appeared 

 like stellar points with no appreciable disk, but surrounded with 

 a nebulous haziness, which would have rendered very uncertain 

 any measurement of an object so minute. Sir W. Herschel 

 thought that Pallas did not exceed 75 miles in diameter. Others 

 have admitted that it might measure a few hundred miles. Ceres 

 is still smaller. 



The obliquity of the orbit of Ceres to the plane of the ecliptic 

 is above 10^, and that of Pallas more than 34|. Both planets, 

 therefore, when most remote from the ecliptic pass far beyond the 

 limits of the zodiac, and differ in obliquity from each other by 

 a quantity far exceeding the entire inclination of any of the older 

 planets. 



It was further observed by Dr. Olbers, that at a point near the 

 descending node of Pallas, the orbits of the two planets very nearly 

 coincided. 



Thus it appeared that all the conditions which rendered these 

 bodies exceptional, and in which they differed from the other 

 members of the solar system, were precisely those .which were 

 164 



