44. 



ADDRESS ON PRESENTING THE GOLD MEDAL OF THE ROYAL ASTRO- 

 NOMICAL SOCIETY TO M. CHARLES DELAUNAY. 



[From the Monthly Notices of the Royal Astronomical Society. Vol. xxx. (1870).] 



GENTLEMEN, It has been announced to you that the Society's Medal 

 has been awarded to M. Ch. Delaunay for his great work on the Theory of 

 the Moon. 



The illness of our excellent President having made it impossible for 

 him to be present on this occasion, the Council have done me the honour 

 to request that I would occupy the chair, and in his stead lay before you 

 the grounds of their award. I have acceded to their wishes with the more 

 readiness because I have given some attention to special branches of the 

 Lunar Theory, and my study of M. Delaunay's work has led me to form the 

 highest opinion of its merits. 



Of all the problems presented to us by physical astronomy none has 

 so much engaged the attention of mathematicians as that of the deter- 

 mination of the motion of our satellite. The theoretical interest as well 

 as the great practical importance of the results, has proved an irresistible 

 attraction, and the mathematical difficulties have merely acted as a stimulus 

 to the invention of various methods of surmounting them. It is fortunate 

 that this has been the case, as the excessive labour involved in any theory 

 of the Moon approaching to completeness, might otherwise have proved too 

 great for human perseverance. The foundations of the theory were laid by 



