238 Trees, Stars, and Birds 



smallest of the eight major planets, with a diameter 

 of only 3000 miles. Its year is 88 days in length and it 



f 



/ARTH MERCURY 



93,0 



/ MILES FROM SUK 



\ 



FIG. 144. Diagram showing the orbit of Mercury. Since Mercury is always 

 near the sun, it is visible only low in the west a short time after sunset or in the 

 east just before sunrise. 



rotates on its axis in the same time, so that the same side 

 is always turned to the sun. 



Mercury will be farthest from the sun as evening star 

 on March 21, July 18, and November 12, 1919, and at 

 intervals of 116 days thereafter. 



Venus. Venus is almost as large as the earth and has 

 been called the earth's twin sister. It is the bright star 

 you have heard called " the evening star " or, when seen 

 before sunrise, " the morning star." At times other 

 planets attract attention as " evening stars " or " morn- 

 ing stars," but they are not so bright as Venus. 



Venus is larger than Mercury and much of the time 

 is higher above the horizon after sunset or before sunrise. 



