126 SEE— THE PAST HISTORY OF THE EARTH. [April 23, 



ADDENDUM ON THE VIEWS OF EULER, 1749. 



Euler's Remarks on the Secular Effects of the Resisting 



Medium upon the Orbital Motion of the Earth, and 



ON THE Origin of the Planets at a Great 



Distance from the Sun. 



In view of the results briefly indicated in Astronomische Nach- 

 ricten, No. 4308, and of the paramount part played by the resisting 

 medium in shaping the orbits of the planets and satellites, as well 

 as the orbits of the attendant bodies in other cosmical systems 

 observed in the immensity of space, some remarks of the celebrated 

 Leonard Euler are of much interest to contemporary astronomers 

 and mathematicians. These remarks are included in the Philosoph- 

 ical Transactions of the Royal Society for 1749, pp. 141-142, under 

 the title : " Part of a Letter from Leonard Euler, Professor of 

 Mathematics at Berlin and F.R.S., to the Rev. Mr. Caspar Wetstein, 

 Chaplain to the Prince of Wales, dated, Berlin, June 28, 1749; read 

 November 2, 1749." And this is followed by a similar extract from 

 a second letter to Wetstein, dated, Berlin, December 20, 1749, read 

 March i, 1750. 



The views of Euler here set forth are very remarkable not only 

 for the insight they show into the mechanism of the heavenly 

 motions, but also into the true mode of origin of our solar system. 

 It must be remembered that, in reaching these views on cosmogony, 

 Euler preceded both Kant (1755) and Laplace (1796), and that he 

 was the first mathematician since Newton to consider the secular 

 effects of a resisting medium. His views on the origin of the 

 planets are therefore free from every possible prejudice, and the 

 direct outcome of the continued action of forces which he believed 

 to be operative in the heavenly spaces. 



Newton seems to have held that the spaces where the planets 

 move are essentially as devoid of matter as a vacuum. This is 

 expressly stated in first paragraph of the General Scholium to the 

 " Principia." Yet he may have believed that some waste matter is 

 diffused in the celestial spaces, for in the paragraph just before the 

 General Scholium, he says : 



