368 A Short History of Astronomy *CH. xin. 



Tables de la Lune (1824 and 1828) were for some time in 

 general use. 



Some special problems of both lunar and planetary theory 

 were dealt with by Simeon Dents Poisson (1781-1840), who 

 is, however, better known as a writer on other branches of 

 mathematical physics than as an astronomer. A very 

 elaborate and detailed theory of the moon, investigated by 

 the general methods of Laplace, was published by Giovanni 

 Antonio Amadeo Plana (1781-1869) in 1832, but unac- 

 companied by tables. A general treatment of both lunar 

 and planetary theories, the most complete that had appeared 

 up to that time, by Philippe Gustave Doulcet de Pontecoulant 

 (1795-1874), appeared in 1846, with the title Theorie 

 Analytique du Systeme du Monde ; and an incomplete 

 lunar theory similar to his was published ^ John William 

 Lubbock (1803-1865) in 1830-34. 



A great advance in lunar theory was made by Peter 

 Andreas Hansen (1795-1874) of Gotha, who published in 

 1838 and 1862-64 the treatises commonly known respectively 

 as the Fundamenta * and the Darlegung^C and produced 

 in 1857 tables of the moon's motion of such accuracy that 

 the discrepancies between the tables and observations in 

 the century 1750-1850 were never greater than i" or 2". 

 These tables were at once used for the calculation of the 

 Nautical Almanac and other periodicals of the same kind, 

 and with some modifications have remained in use up to 

 the present day. 



A completely new lunar theory of great mathematical 

 interest and of equal complexity was published by Charles 

 Delaunay (1816-1872) in 1860 and 1867. Unfortunately 

 the author died before he was able to work out the 

 corresponding tables. 



Professor Newcomb of Washington ( 283) has rendered 

 valuable services to lunar theory as to other branches of 

 astronomy by a number of delicate and intricate calcula- 

 tions, the best known being his comparison of Hansen's tables 

 with observation and consequent corrections of the tables. 



* Fundamenta Nova Investigationis Orbitae Verae quant Luna 

 perlustrat. 



f Darlegung der theoretischen Berechnung der in den Mondtafeln 

 angewandten Storungen. 



