That devised by Laplace has ceased to be satisfactory. Its simplicity, at first sight so seductive, leaves it at a disadvantage compared with the intricacy of the effects it was designed to elicit. The relations claiming explanation have multiplied with the progress of research. Those of the dynamical order were alone attended to by the geometers of the eighteenth century, and even they have grown recalcitrant; while those of a physical and chemical kind have proved wholly unmanageable. It has, indeed, become abundantly clear that the series of operations described by Laplace could scarcely, under the most favourable circumstances, have been accomplished, and in a thin nebulous medium would have been entirely impossible. The nebular cosmogony has not, then, stood 'Foursquare to all the winds that blew.' Its towers and battlements have crumbled before the storms of adverse criticism. It survives only as a wreck, its distinctive features obliterated, although with the old flag still flying on the keep. In the next chapter we shall attempt a survey of the works set on foot for its reconstruction. FOOTNOTES: [Footnote 10: Presidential Address to the British Association, Johannesburg, August 30, 1905.] [Footnote 11: _Comptes Rendus_, tom. lii., p. 481.] [Footnote 12: _Astrophysical Journal_, vol. xi., p. 103.] [Footnote 13: Moulton, _Astrophysical Journal_, vol. xi., p. 110.] [Footnote 14: Nolan, _Nature_, vol. xxxiv., p. 287.] [Footnote 15: _Bulletin Astronomique_, tom. ii., p. 223.] CHAPTER IV THE NEBULAR HYPOTHESIS VARIED AND IMPROVED 'Restorations' often go very far. Things may be improved beyond recognition, nay, out of existence. So it has happened to the nebular hypothesis. _Stat nominis umbra._ The name survives, but with connotations indefinitely diversified. The original theme is barely recalled by many of the variations played upon it. Entire license of treatment prevails. The strict and simple lines of evolution laid down by Laplace are obliterated or submerged. Some of the schemes proposed by modern cosmogonists are substantially reversions to Kant's _Natural History of the Heavens_; the long-discarded and despised Cartesian vortices reappear, with the éclat of virtual novelty, in others; nor are there wanting theories or speculations reminiscent even of Buffon's cometary impacts. Moreover, the misleading fashion has come into vogue of bracketing Kant with Laplace as co-inventor of the majestic and orderly plan of growth commonly designated the 'nebular hypothesis.' This has been, and is, the source of much hurtful confusion. Save the one fundamental idea--and that by no means their exclusive property--of ascribing unity of origin to the planetary system, Kant's and Laplace's evolutionary methods had little in common. Their postulates were very far from being identical; they employed radically different kinds of 'world-stuff'; and the 'world-stuff' was subjected, in each case, to totally dissimilar processes.