MERCURY AKD VENUS. 



distance from the sun is 36,770,000 miles, and it performs 

 its revolution in eighty-eight days. 



FI6. 5. 



This planet is but seldom seen with the naked eye ; for, 

 being so (comparatively) near to the sun, it sets before 

 dark, and does not rise till the grey of morning makes it 

 scarcely visible. Nothing notable has been discovered on 

 its surface. 



Venus is the second in rotation from the sun, and revolves 

 round it, at a distance of 68,750,000 miles, in 224-|- days. 

 The diameter of Yenus is about 7760 miles, it is therefore 

 nearly the volume of the earth. This is the brightest planet 

 seen in the heavens, for although much smaller than many 

 others, its comparative nearness to the sun and earth causes 

 it to appear larger and brighter to the eye. Venus is the 

 evening and morning star ; for when to the west of the sun, 

 it rises before it, and is then called " the morning star " (or, 

 formerly, " Lucifer"), but when it is to the east of the sun, 

 it sets after twilight is gone, and is called " the evening 

 star," or " Hesperus." 



These two planets, Mercury and Venus, have " phases " 

 (like the moon), or certain positions in which the whole 

 of the side illuminated by the sun is seen from the earth, 

 and other positions in which it is seen sideways ; the planet 

 is then said to be in " quadrature," as may be seen at Q Q, 

 fig. 6. Mercury and Venus, being between the sun and the 

 earth, are called "inferior" planets, while those whose 



