I9I0.] RESEARCHES IN COSMICAL EVOLUTION. 209 



mogony resulting from the dynamical principle of the conservation 

 of areas, and concluded that the classic nebular hypothesis was 

 vitiated by a fallacy. 



Like most negative critics, Babinet was beset by the weakness 

 that he could tear down but could not build up. And as he sub- 

 stituted nothing for the theory of Laplace, the valuable criticism 

 which he had made was scarcely noted by his contemporaries, and 

 remained practically unknown to subsequent investigators. Thus 

 we find in the writings of Lord Kelvin, Newcomb, Darwin, Tis- 

 serand and Poincare no mention of the eminently useful criterion 

 which Babinet had proposed in 1861 ; and it was allowed to slumber 

 half a century in a forgotten number of the Comptes Rendus. 



Looking back over this strange state of affairs, we naturally 

 ask ourselves why Babinet did not proceed further with his investi- 

 gations. To this question no certain answer can be returned, but 

 it is probable that his inability to account for the remarkable round- 

 ness of the planetary orbits, which Laplace had explained by the 

 process of gentle detachment, made him hesitate to go any further, 

 and he gave up the effort in despair. 



More than forty years ago the American astronomers Kirkwood 

 and Pierce reached the conclusion that a mass so rare as the solar 

 nebula must have been when it was expanded to fill the orbits of 

 the planets, as imagined by Laplace, could not exert hydrostatic 

 pressure so as to detach rings or zones of vapor; and they urged 

 this objection as essentially fatal to the Laplacian theory. Here 

 again the criticism was of the negative kind, like most of the 

 criticism of Laplace's theory which appeared before and since their 

 epoch ; and it therefore shared the inherent weakness of all criti- 

 cism which is not accompanied by work of constructive character. 

 It does little good to break up our mental images if we cannot put 

 better ones in their places ; tearing down is easy, but building new 

 structures much more difficult. And so long as the criticism was 

 of purely negative character, it naturally failed to supersede 

 Laplace's theory with a better one, and, by default, the ring theory 

 has continued to hold its ground almost up to the present time. 



It is not necessary to go into the details of more recent destruc- 



PROC. AMER. PHIL. SOC, XLIX. I94 N, PRINTED JULY 27, I9IO. 



