Contents xxv 



PAGE 



277. Bessel : his improvement in methods of re- 



duction : his table of refraction : the Funda- 

 menta Nova and Tabulae Regiomontanae . 359 

 278. The para lax of 6 1 Cygni : its distance . . 360 



279. Hendersons parallax of a Centauri and Struves 



of Vega : later parallax determinations . 362 

 280. Star catalogues : the photographic chart . . 362 



281-4. The distance of the sun : transits of Venus : 

 observations of Mars and of the minor planets 

 in opposition : diurnal method : gravitational 

 methods, lunar and planetary : methods 

 based on the velocity of light : summary of 



results 363 



285. Variation in latitude : rigidity of the earth . 367 



286. Gravitational Astronomy. Lunar theory : Danwi- 

 seau,Poisson, Ponte'coulant, Lubbock,Hansen, 

 Delaunay, Professor Newcomb, Adams, Dr. 

 Hill 367 



287. Secular acceleration of the moon's mean motion : 



Adams's correction of Laplace : Delaunay's 

 explanation by means of tidal friction . . 369 



288. Planetary theory : Leverrier, Gylde'n, M. Poincare 370 



289. The discovery of Neptune by Leverrier and Dr. 



Galle : Adams's work 371 



290. Lunar and planetary tables : outstanding dis- 



crepancies between theory and observation 372 



291. Cometary orbits : return of Halley's comet in 



1835 : Encke's and other periodic comets . 372 



292. Theory of tides : analysis of tidal observations 

 by Lubbock, Whewell, Lord Kelvin, and 

 Professor Darwin : bodily tides in the earth 

 and its rigidity 373 



293. The stability of the solar system . . . 374 



294. Descriptive Astronomy. Discovery of the minor 

 planets or asteroids : their number, dis- 

 tribution, and size 376 



295. Discoveries of satellites of Neptune, Saturn, 

 Uranus, Mars, and Jupiter, and of the crape 

 ring of Saturn 380 



296. The surface of the moon : rills : the lunar atmo- 

 sphere 382 



