284

THE MINOR PLANETS.

the Sun. They would, of course, pass at different distancesbeyond the Sun, and at different epochs of time ; but, to anobserver placed at the point of explosion, or directly between itand the Sun, the points of which we speak would all apparentlylie in one straight line, and the fragments would consequentlyappear to pass, once in each revolution, through the point inwhich the direction of that, line would intersect the celestialsphere. This is otherwise expressed by saying that they atsuch times would have the same celestial longitude.

Now it is exceedingly remarkable, as we have mentioned,that the above two conditions were approximately satisfied bythe orbits of the four Minor Planets first discovered ; in fact,the third, Juno, and the fourth, Vesta, were actually found, theone in the constellation of the Whale, and the other in that ofthe Virgin, as the result of a search made in those two oppositeparts of the heavens, the advisability of which was suggested,according to the principle which we have just explained, by acomparison of the orbits of the first two.

The hypothesis put forward by Olbers , who at the beginningof the present century was most active and interested in thesearch for these bodies,—viz., that they might be the frag-ments of an exploded planet,—was therefore received with muchattention, and apparently 'supported by the above discoveries.

But, as time has gone on, it has been proved that the orbitsof very many, instead of continuing to pass near to any onepoint of the heavens, and through a longitude exactly oppositeto it, are so separated, that the nearest distance of some is(as we have stated) from 50 to 70 millions of miles greaterthan the farthest distance of others ; while the ovalness, andthe positions of the planes, of the orbits, vary within verywide limits. It has also been found, as we hope our readersby this time remember, that the Minor Planets are spread overa region not much less than 300,000,000 miles in width. Thehypothesis suggested by Olbers has consequently been givenup by all, or nearly all, astronomers of note. It is no doubttrue that, if the orbits had at first been such as we havedescribed, their mutual perturbations would have graduallychanged them ; but the change would have been in itself so