284 SCIENTIFIC THOUGHT. 



The two lines of speculation, originated by Leibniz 

 and Kant as to the genesis of things on this earth and 

 in the universe, mark two distinct ways of approaching 

 the genetic problem. They were both isolated, and it 

 was not till well on in the course of our century that 

 they were again taken up and independently developed 

 the one by geologists, the other by physical astronomers. 

 They remained for a long time without mutual influence ; 

 till, within the last generation, they were brought to- 

 gether, their different results deduced, and a reconcilia- 

 tion attempted. To this I shall revert later on. Forty 

 years after Kant, Laplace put forward his so-called 

 nebular hypothesis at the end of the popular exposition 

 which he gave of his mechanical theory, of the heavens. 

 He apparently knew nothing of Kant's attempt, and his 

 views differ materially from those of Kant, in so much 

 as he assumes in the rotating nebular mass an attracting 

 nucleus from which, in the course of condensation through 

 attraction, the planetary rings and bodies were thrown 

 off as the centrifugal velocity balanced the attracting 

 forces. For a long time this sketch of a possible 

 genesis of the planetary system was paraded in popular 



work. The merits of Kant have only 

 been tardily recognised ; they were 

 unknown to Laplace, and only 

 imperfectly known to more recent 

 authorities, such as Helmholtz and 

 Lord Kelvin, who were fully pre- 

 pared to do him justice. Lord 



controversy which took place be- 

 tween him and Huxley on " Geo- 

 logical time " the theories of Kant 

 were frequently referred to. See 

 his lecture on "Geological Time," 

 1868 (loc. cit., p. 10, &c.) ; Huxley 

 on "Geological Reform," 1869 (re- 



Kelvin, in his Rede Lecture of | printed in ' Lay Sermons,' No. XI.) 



1866, refers to Kant as the first : The best account in the English 



to publish " any definite estimate : language of Kant's contributions 



of the possible amount of the I to cosmogony will be found in an 



diminution of rotatory velocity article by G. F. Becker in the 5th 



experienced by the earth through : vol., 4th series, of the 'American 



tidal friction'' ('Pop. Lects. and Journal of Science,' 1898. 

 Addr.,' vol. ii. p. 65), and {in the 



