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NATURE-STUDY REVIEW [17:1— Jan., 1921 



Owinjj: to its eastward motion, a daily retardation of the moon's 

 rising and setting occurs, being about 50 J^ minutes. 



Among some of the most wonderful phenomena of the heavens 

 are the limar eclipses. They are produced only when the new or 

 the full moon is at or very near one of the nodes. If the orbits of 

 the earth and the moon were exactly on the same plane, an eclipse 

 would take place every new or full moon. However, the plane of 

 the moon's orbit is inclined to the plane of the earth's orbit at an 

 angle of about five degrees. Besides the moon's nodes are not 

 stationary, but have a daily backward motion, owing to the attrac- 

 tion of the sun on the earth and moon. As a result of this back- 

 ward motion of the moon's nodes, eclipses occur on average about 

 19 days earlier every year. 



The moon's 



surface 



showing the 



craters 



Mercator 



and 



Campanus. 



Photo after 

 Nasmyth 



