If Jupiter's influence was a factor in the separation of planetules at the sun's equator, may not similar clusters exist in other parts of our system? The hypothesis is certainly by no means improbable. For anything we know to the contrary a group may circulate between Jupiter and Saturn; such bodies, however, could not be discovered--at least not by ordinary telescopes--on account of their distance. The Zodiacal Light, it has been suggested, may be produced by a cloud of indefinitely small particles related to the planets between the sun and Mars. The rings of Saturn are merely a dense asteroidal cluster; and, finally, the phenomena of luminous meteors indicate the existence of small masses of matter moving with different velocities in interstellar space. NOTE B. THE ORIGIN AND STRUCTURE OF COSMICAL RINGS. The general theory of cosmical rings and of their arrangement in sections or clusters with intervening chasms may be briefly stated in the following propositions: I. Whenever the separating force of a primary body on a secondary or satellite is greater than the central attraction of the latter on its superficial stratum, the satellite, if either gaseous or liquid, will be transformed into a ring. EXAMPLES.--Saturn's ring, and the meteoric rings of April 20, August 10, November 14, and November 27. See Payne's _Sidereal Messenger_, April, 1885. II. When a cosmical body is surrounded by a ring of considerable breadth, and has also exterior satellites at such distances that a simple relation of commensurability would obtain between the periods of these satellites and those of certain particles of the ring, the disturbing influence of the former will produce gaps or intervals in the ring so disturbed. See "Meteoric Astronomy," Chapter XII.; also the _Proceedings of the American Philosophical Society_, October 6, 1871; and the _Sidereal Messenger_ for February, 1884; where the papers referred to assign a physical cause for the gaps in Saturn's ring. THE END. FOOTNOTES: [1] The discoverer, Piazzi, was not, as has been so often affirmed, one of the astronomers to whom the search had been especially committed. [2] Massalia was discovered by De Gasparis, at Naples, Sept. 19, 1852, and independently, the next night, by Chacornac, at Marseilles. The name was given by the latter. [3] Astr. Nach., No. 932. [4] Monthly Notices, vol. xxvii. [5] Annals of the Obs. of Harv. Coll., 1879. [6] This ingenious idea may be readily extended. The least distance of Æthra is less than the present aphelion distance of Mars; and the maximum aphelion distance of the latter exceeds the perihelion distance of several known asteroids. Moreover, if we represent the orbits of the major planets, and also those of the comets of known periods, by material rings, it is easy to see that the major as well as the minor planets are all linked together in the manner suggested by D'Arrest.