xliv KANT'S UNIVERSAL NATURAL HISTORY 



ence in the period of revolution must have become 

 imperceptible. 1 Of course, Kant knew nothing of 

 this hypothesis in 1754; but it is relevant here as 

 showing what had been passing in Euler's mind. 

 Confirmation of this view is also found by reference 

 to the nature of the subjects then being dealt with by 

 Euler in some of his papers to the Berlin Academy. 



(4) Very remarkable is it that Kant seems to have 

 abandoned his early theory altogether, and that he 

 worked out later exactly the opposite view in support 

 of Euler's conjecture. The said Supplement II., to his 

 Physical Geography, is entitled ' Of the Acceleration 

 of the daily rotation of the earth ' ; and accepting this 

 idea, on Euler's authority, he founds it upon the view, 

 then becoming prevalent, that the central mass of 

 the earth was in a molten or fluid state, so that the 

 heavier particles were continually falling towards the 

 centre, carrying with them a greater velocity of 

 rotation than the lighter particles which might be 

 ascending from the centre, and which would tend to a 

 certain internal relative retardation. He also sug- 

 gested the increasing contraction of the mass of the 

 earth as a cause of its increasing rotational speed, 

 yet he .does not confidently assert or found upon it. 

 But Kant in this late * Note ' holds quite clearly to 

 the former cause, and consequently to the view of the 

 continual acceleration of the rotation. 2 Kant's later 



* Kant's Werke, R. vi., 786. 



2 Lord Kelvin, as is well known, has pointed out that the increase of 

 the mass of the earth by meteoritic deposit will cause retardation, but 

 this did not occur to Kant. 



