106 COSMOS. 



ecliptic, depeni, as theoretical astronomy proves, upon the 

 configuration. 



The absolute magnitudes of the planets, and their distance 

 from the Earth, determine their apparent diameter. We 

 have, therefore, to arrange the planets according to their ab- 

 solute (actual) magnitudes, proceeding from the larger to 

 the smaller : 



The small planets with involved orbits, of which the larg- 

 est appears to be Pallas and Vesta : 



Mercury, Neptune, 



Mars, Uranus, 



Venus, Saturn, 



Earth, Jupiter. 



The apparent equatorial diameter of Jupiter, at a mean 

 distance from the Earth, is 38"-4, while that of Venus, which 

 is nearly equal in magnitude to the Earth, is only 16*9"; 

 that of Mars, 5"*8. But the apparent diameter of the disk 

 of Venus increases in the inferior conjunction to 62", while 

 that of Jupiter attains only an increase to 46". It is neces- 

 sary to call to mind in this place that the point of the orbit 

 of Venus at which it appears to us with the brightest light, 

 falls between the inferior conjunction and her greatest digres- 

 sion from the Sun, because in that position the small lumin- 

 ous crescent gives the most intense light, on account of its 

 greatest proximity to the Earth. Upon the average, Venus 

 appears the most beautifully luminous, even casting shadows 

 in the absence of the Sun, when at a distance of 40° east or 

 west from the Sun ; the apparent diameter then amounts to 

 only 40", and the greatest width of the illuminated phase is 

 scarcely 10". 



Apparent Diameter of Seven Planets. 



Mercury at a mean distance 6" - 7 (oscillates from 4""4 to 12") 



