12 GENERAL SCIENCE 



its period of revolution, it always turns the same side 

 toward the earth. 



Phases of the Moon. --When the moon is in that 

 part of its orbit nearest the sun, it is almost between 



FIG. 9. The Moon. 

 Photographed at the Lick Observatory. 



the earth and the sun. The side illuminated is then 

 turned away from the earth and we see but a mere fringe 

 of illumination, a thin crescent. We call this phase the 



