xlvi KANT'S UNIVERSAL NATURAL HISTORY 



equalisation of their rotations. According to Kant's 

 calculation, there would be required 2*j\ million 

 years before this condition would be reached. All 

 this is to be found explicitly in Kant, although it 

 is commonly supposed that it is all matter of much 

 later discovery, and it furnishes very striking evi- 

 dence of the original and logical character of his 

 genius. Even the recognition of the great retarding 

 tides that swept round the Moon, in the train of 

 the Earth's attraction upon its primitive fluid state, 

 stands quite clearly before us already in Kant's 

 early discovery. 



The later history of this peculiarly interesting 

 question is well known ; it is to be found indicated 

 in all our best text-books, and even in popular 

 writings on the subject. Laplace put forth another, 

 but more hypothetical solution of the question in 

 1789, founded upon a characteristic theory of the 

 variation of the form of the Earth's orbit within 

 certain definite limits. In 1824 he gives the same 

 view as Kant had done. The distinguished German 

 physicist, J. R. Mayer of Heilbronn, again professes 

 to give as original the same solution of the question, 1 

 and in almost the same terms, as Kant; and the 

 Kant solution of 1754 is compared in parallel 

 columns with the Mayer solution of 1848 by 

 Zollner, with an almost cruel conscientiousness. 2 

 On nth December, 1865, the French academician, 

 M. Delaunay, submitted a Treatise to the French 



1 Dynamik des Himmels^ 1848. 2 Natur der Cometen^ p. 472. 



