RESEARCHES OX JUPITER'S SATELLITES. 341 



vouthful and which communicated itself to able coad- 







jtitors. Laplace solved the celebrated problem of the 

 longitude more completely than could have been hoped 

 for in a scientific point of view, with greater precision 

 than the art of navigation in its utmost refinement de- 

 manded. The ship, the sport of the winds and tem- 

 pests, has no occasion, in the present day. to be afraid 

 of losing itself in the immensitv of the ocean. An in- 







telliirent glance at the starrv vault indicates to the pilot, 







in everv place and at everv time, his distance from the 



L 



meridian of Paris. The extreme perfection of the ex- 

 isting tables of the moon entitles Laplace to be ranked 

 amouir the benefactors of humanitv.* 







In the bosinninir of the vear 1611. Galileo supposed 







that he found in the eclipses of Jupiter's satellites a sim- 

 ple and rigorous solution of the famous problem of the 

 longitude, and active negotiations were immediately com- 



c? 



menced with the view of introducing the new method on 

 board the numerous vessels of Spain and Holland. 

 These negotiation? failed. From the discussion it plainly 

 appeared that the accurate observation of the eclipse* 

 of the satellites would require powerful telescopes ; but 



^ The theoiv - - of Laplace formed the basis of Rurek- 



hardt's Lunar Table?, which are eh yed in computing the 



place? of the moon for the Xantieal Almanac and other F.phemer - 

 These tables v ; . by an empiric equation, sr.__ sto : . for the 



purpose of representing an in y of lor - waedto 



affect the mean longitude of the moon. No satisfaet ".aviation 



of the origin of this inequality could be discovered by any geometer, 

 although it form, . : - f much toilsom; - .tion 



throughout the present rentury, until at 1; M. Han? d it 



to arise from a combination of two inequa'.i: - sturbing 



action of Venus. The period. :hese inequalities > ." ; :ars, 



and that of t'. . : is -Jot* years. The maximum value o;" 



former i? 27 "-4, and : the latter i- - : ^r. 



