3. Besides these extreme members of the group, our table contains eighty-six minor planets, all of which are included between the distances 2·26 and 3·16; the mean interval between them being 0·0105. The distances are distributed as follows: 2·26 to 2·36 6 minimum. 2·36 to 2·46 19 maximum. 2·46 to 2·56 4 minimum. 2·56 to 2·66 16 } 2·66 to 2·76 16 } maximum. 2·76 to 2·86 8 2·86 to 2·96 4 } minimum. 2·96 to 3·06 3 } 3·06 to 3·16 10 maximum. The clustering tendency is here quite apparent. 4. The three widest intervals between these bodies are-- (_a_) between Leucothea and Pales 0·0785, (_b_) " Leto and Terpsichore 0·0755, (_c_) " Thetis and Hestia 0·0525; and these, it will be observed, are the three remaining distances, indicated on a previous page, at which the periods of the primitive meteoric asteroids would be commensurable with that of Jupiter. Now, if the original ring consisted of an indefinite number of separate particles moving with different velocities, according to their respective distances, those revolving at the distance 2·4935--in the interval between Thetis and Hestia--would make precisely three revolutions while Jupiter completes one. A planetary particle at this distance would therefore always come in conjunction with Jupiter in the same parts of its path: consequently its orbit would become more and more eccentric until the particle itself would unite with others, either exterior or interior, thus forming an asteroidal nucleus, while the primitive orbit of the particle would be left destitute of matter, like the interval in Saturn's ring. 5. If the distribution of matter in the zone was originally nearly continuous, as in the case of Saturn's rings, it would probably break up into a number of concentric annuli. On account, however, of the great perturbations to which they were subject, these narrow rings would frequently come in collision. After their rupture, and while the fragments were collecting in the form of asteroids, numerous intersections of orbits and new combinations of matter would occur, so as to leave, in the present orbits, but few traces of the rings from which the existing asteroids were derived. A comparison, however, of the elements of Clytie and Frigga shows a striking similarity; and Professor Lespiault has pointed out a corresponding likeness between the orbits of Fides and Maia. For these four asteroids the nodal lines and also the inclinations are nearly the same; while the periods differ by only a few days. It is probable, therefore, that they are all fragments of the same narrow ring. Finally, as they all move nearly in the same plane, they must at some future time approach extremely near each other, and perhaps become united in one large asteroid. CHAPTER XIV. ORIGIN OF METEORS--THE NEBULAR HYPOTHESIS.