The organization of the solar kingdom, as disclosed by modern research, is greatly more varied and complex than Laplace took it to be. His genetic scheme was, indeed, no sooner promulgated than deviations from the regularity and unanimity of movement upon which it was based began to assert their inconvenient reality. They have since multiplied; and, emerging to notice under the most unlikely aspects, they occasion incongruities which tax, for their explanation, all the resources and audacities of the most inventive cosmogonists. Let us briefly consider their nature. The swarm of asteroids that bridge the gap between Mars and Jupiter revolve, it is true, with the general swirl of planetary movement; but they use a large license as regards the shape and lie of their orbits. And their partial exemption from the rules of the road becomes entire for comets and meteors, which have nevertheless proved themselves to be aboriginal in our system by their full participation in its proper motion. Finally, several of the major planets set convention at defiance in the arrangement of their several households, and thereby intimate departures from the supposed normal course of development so frequent and so considerable as to shake belief even in its qualified prevalence. Thus, the anomalously short period of the inner satellite of Mars, besides throwing doubt over its own mode of origin, tends to obscure the history of its more sedately circulating associate. Deimos cannot have been thrown off from its primary under conditions materially different from those attending the birth of Phobos. The sub-systems of Uranus and Neptune exhibit, moreover, eddies of retrograde movement suggesting primitive disturbances of a fundamental kind; while the surprising disclosures connected with Saturn's firstborn and furthest satellite, photographically detected by Professor W. H. Pickering in 1898, have added one more knotted thread to the tangled skein we would fain unravel. Until acquaintance was made with Phœbe, counterflows of revolution within the same satellite-family were unknown, and, if contemplated at all, would have been scouted as impossible. One ternary star, to be sure--ξ Scorpii--had been recognised as probably owning an immediate and a more remote attendant, in oppositely directed orbital movement;[103] but the cases are in many ways disparate, and the analogy, though instructive, is imperfect.