r. 



8 COSMOS. 



In the enumeration of the 22 principal p anets, of which 

 6 only were known before the 13th of March, 1781, the 14 

 small planets, which are sometimes termed co-planets or as- 

 teroids, and describe intersecting orbits between Mars and 

 Jupiter, have been distinguished from the 8 larger planets 

 by the use of smaller type. 



The following occurrences constitute main epochs in the 

 more recent history of planetary discoveries. The discovery 

 of Uranus, as the first planet beyond Saturn's orbit, by Will- 

 iam Herschel, at Bath, on the 13th of March 1781, who rec- 

 ognized it by its motion and disk-like form ; the discovery of 

 Ceres — the first observed of the smaller planets — on the 1st 

 of January, 1801, by Piazzi, at Palermo ; the recognition of 

 the first interior comet,-by Encke, at Gotha, in August, 1819, 

 and the prediction of the existence of Neptune by Leverrier, 

 at Paris, in August, 1846, by the calculation of planetary dis- 

 turbances, as well as the discovery of Neptune by Galle, at 

 Berlin, on the 23d of September, 1846. These important 

 discoveries have not only tended directly to extend and en- 

 rich our knowledge of the solar system, but have further led 

 to numerous other discoveries of a similar nature ; as, for in- 

 stance, to the knowledge of five other interior comets (of Bi- 

 ela, Faye, De Yico, Brorsen, and D' Arrest, between 1826 and 

 1851), and of thirteen small planets, three of which, Pallas, 

 Juno, and Vesta, were discovered from 1801 to 1807, and aft- 

 er an interval of fully thirty-eight years, since Hencke's for- 

 tunate and preconceived discovery of Astrsea, on the 8th of 

 December, 1845, the nine others were discovered, in rapid suc- 

 cession, by Hencke, Hind, Graham, and De Gasparis, from 

 1845 to the middle of 1851. The attention of observers has 

 of late been so extensively directed to the cometary world, that 

 the orbits of thirty-three newly-discovered comets have been 

 calculated during the last eleven years ; hence, nearly as 

 many as had been determined during the previous forty years 

 of this century. 



