TRANSLATOR'S INTRODUCTION Ixxiii 



Herschel must undoubtedly be recognised as the 

 greatest observational Astronomer of modern times, 

 but his power as a constructive thinker in his 

 own sphere was incomparably inferior to that of 

 Kant. 



7. Kant and Laplace. In 1796, forty-one years 

 after Kant had produced his Natural History and 

 Theory of the Heavens, Laplace (1749-1827) set 

 forth the first outline of his beautiful and fascinating 

 Nebular Hypothesis in the last chapter of his 

 popular Exposition of the System of the World. It 

 was completed in the third edition (1808), by the 

 addition of a paragraph on the formation of the 

 planets by the rupture of the rings of vapour out 

 of which they were formed. It remained in this 

 form in the fourth edition of 1813; but in the fifth 

 edition, the last published in his lifetime, evidently 

 from regard to its hypothetical character, the ex- 

 position of the hypothesis was removed from the 

 text and made to form the celebrated 'Note VII.,' 

 and it is so reprinted in the sixth edition of 1836, 

 nine years after the death of Laplace. The Hypo- 

 thesis is also referred to summarily by Laplace in 

 the fifth volume of the Mecanique Celeste (1825), 

 in the last paragraph of the last chapter of Book 

 XIV. It is expounded with all the lucidity and 

 precision of Laplace's scientific style, but apolo- 

 getically 'with the distrust which all that is not a 

 result of observation or of calculation should inspire.' 

 Notwithstanding this caveat, Laplace's brilliant 



