TRANSLATOR'S INTRODUCTION xliii 



its contents (see last sentence of the paper, infra, 

 pp. 10, u). 



(3) Lord Kelvin has rightly pointed out that no 

 previous mathematician or physical astronomer had 

 discovered or anticipated Kant's solution and with 

 this Professor Tait and M. Wolf agree; so that it 

 appears to be absolutely original. 1 But it is relevant 

 to raise the question, which very naturally occurs, as 

 to how, and on whose suggestion, the Berlin Academy 

 came to propose this problem at that time? In the 

 absence of direct evidence, we can only proceed by 

 inference, and it appears to me that it was Euler who 

 most probably raised the question in this form, 

 although Maupertuis may have actually so formulated 

 it. We find a hint of this in a much later work 

 of Kant, in his Lectures on Physical Geography, 

 published by Rink in 1802-3, but containing matter 

 which had gathered in Kant's hands through many 

 years. In the Second Supplement to this work, 

 printed from Kant's own MS., he mentions that 

 Euler had advanced the theory of the gradual 

 shortening of the course of the year, and in a letter 

 to the Danish Bishop Pontoppidan (1698-1764) 

 (who was made Bishop of Bergen in 1747, and Vice- 

 Chancellor of the University of Copenhagen in 1755), 

 he had expressed the hypothesis that the daily 

 rotation of the earth had perhaps been gradually 

 shortened from causes unknown, whereby the differ- 



1 Lord Kelvin, The Age of the Earth, p. 7 ; Tait, Recent Advances 

 cf Physical Science, p. 8; Wolf, Hypotheses, p. 173 n. 



