THE SOLAR REGION. . 357 



22 PRINCIPAL PLANETS (MERCURY, VENUS, 

 EARTH, MARS ; Flora, Victoria, Vesta, Iris, Metis, Hebe, 

 Parthenope, Irene, Astraa, Egeria, Juno, Ceres, Pallas, 

 Hygiea; JUPITER, SATURN, URANUS, NEPTUNE); 



21 SATELLITES (1 belonging to the Earth, 4 to Jupiter, 

 8 to Saturn, 6 to Uranus, 2 to Neptune) ; 



197 COMETS, whose orbits have been calculated. Of 

 these 6 are interior ; i. e. such as have their aphelia inclosed 

 within the outermost of the planetary orbits, viz. that of 

 Neptune: we may very probably add to these; 



THE RING OF THE ZODIACAL LIGHT, which probably 

 lies between the orbits of Venus and Mars ; and likewise, 

 according to the opinion of numerous observers : 



THE SWARMS OF THE METEOR- ASTEROIDS which more 

 especially intersect the Earth's orbit at certain points. 



In the enumeration of the 22 principal planets, of which 

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

 small planets, which are sometimes termed co-planets or 

 asteroids, 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 

 William Herschel at Bath, on the 13th of March, 1781, who 

 recognized it by its motion and disc-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 disturbances, as well as the discovery of Neptune 



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