78 A CENTURY'S PROGRESS IN ASTRONOMY. 



his death the subject was taken up by Charles 

 Theodore Damoiseau (1768-1846), and the most 

 important advance was made by Giovanni 

 Antonio Amadeo Plana (1781-1864), the director 

 of the Turin Observatory, who published in 1832 

 a very complete lunar theory. The work of 

 Plana was followed by that of Peter Andreas 

 Hansen (1795-1874), whose lunar tables were 

 used for the Nautical Almanac, and whom 

 Professor Simon Newcomb considers to be 

 the greatest master of celestial mechanics since 

 Laplace. The theory of the Moon's motion was 

 worked out in detail by the famous astronomer 

 Charles Eugene Delaunay (1816-1872), who 

 from 1870 till 1872 occupied the post of 

 director of the Paris Observatory. Delaunay 

 was about to work out the lunar tables when, 

 in 1872, he was accidentally drowned by the cap- 

 sizing of a pleasure-boat at Cherbourg. The 

 work accomplished in this direction by Simon 

 Newcomb (born 1835) is of great importance, 

 particularly in his correction of Hansen's tables. 

 John Couch Adams (1819-1892), one of the dis- 

 coverers of Neptune, while at work on the lunar 

 theory, had occasion to correct Laplace's sup- 

 posed solution of the acceleration of the lunar 

 motion. On going over the calculation Adams 

 found that several quantities, omitted by Laplace 



