\C A Synopsis of the principal 



nodes has an apparent motion in longitude, according to 

 the order of the signs, of 26'',8 in a year, or 44' 4r',5 in a 

 century. 



The rotation on his axis is performed in \^ 0^ 39' 2l",S : 

 and his axis is incHned to th^ ecliptic in an angle of 59"* 

 41' 49",2. 



[His mean diameter is equal to 4398 miles: consequently 

 he is rather more than half the size of our Earth.] 



His mass, compared with that of the Sun considered as 

 unity, is ^-jt^^^- 



[The proportion of light and heat, received by hnn from 

 the. Sun, is '43 : that received by the Earth being considered 

 as unity.] 



He has a very dense but moderate atmosphere: and he is 

 not accompanied by any satellite. 



As viewed from the Earth, the motion of Mars appears 

 sometimes retrograde. The mean arc which he describes 

 in this case is 16° 12': and its mean duration is about 73 

 days. This retrogradation commences, or finishes, when 

 the planet is not more than 136° 48' from the Sun. 



Mars changes his phases somewhat in the same manner 

 as the Moon does from her first to her third quarter, ac- 

 cording to his various positions with respect to the Earth 

 and the Sun : but, he never becomes cornicular, as the 

 Moon does when near her conjunctions. His mean appa-' 

 rent diameter is 9",7 : which augments in proportion as the 

 planet approaches its opposition, when it is equal to 

 «9",2. 



His parallax is nearly double that of the Sun. 



Jupiter. 



Jupiter is, next to Venus, the most brilliant of all the 

 planets : whom he sometimes however surpasses in bright- 

 ness. He performs his sidereal revolution in 4332** 14*^ 

 18'41",0; or in 11-862 Julian years. But this period is 

 subject to some inequaruies. He performs his mean syno- 

 dical revolution in about 399 days. 



His mean distance from the Sun is 5-203 ; that of the 

 Earth being considered as unity. This makes his mean di- 

 stance above 48.5 millions of miles. 



The eccentricity of his orbit is '0482 j half the major 

 axis being considered as unity. 



His mean longitude at the commencement of the present 

 century wis in 3' 22° 0' 36", 1 . 



The longitude of his perihelion was, at the same time, 

 in 0» 11° 8' 35", 1: but the line of the apsides has an ap- 

 parent 



