The Primary Planets. 



305 



TABLE of the duration of the synodical revolu- 

 tion of the primary planets, compared with 

 that of their periodical revolutions. 



The two inferior planets, Mercury and Venus, 

 as well as three of the superior, Mars, Jupiter, 

 and Saturn, were known to the early astrono- 

 mers. The Georgium Sidus, or Uranus, was 

 discovered in the year 1781, by Dr. Herschell ; 

 Ceres was discovered the first day of the present 

 century, by Mr. Piazzi, an Italian astronomer; 

 Pallas, by Dr. Olbers of Bremen, in 1802 ; Juno, 

 by Mr. Harding, at Lilienthal, in 1804; and 

 Vesta, by Dr. Olbers, in the spring of the year 

 1807. 



The general character and appearance of the 

 principal planets will be best understood by a 

 reference to Plate XXVII. and therefore few 

 observations will be necessary on this subject. 



MERCUBY, from his nearness to the sun, is 



