5 i6 



SCIENTIFIC RECREATIONS. 



time as she turns upon her own axis, and always presents one side to us 

 when she appears. Any one can ascertain this by putting a candle upon a 

 round table, and walk round it facing the candle. The experimentalist will 

 find that he will turn upon his own axis as well as turn around the table. 

 Thus we shall see how the moon changes, for to be as changeable as the 

 moon is proverbial. These different aspects or phases we shall now proceed 

 to explain. 



The time intervening between one "new" moon and another is 

 29 d , I2 h , 44 m , 2 3 , and is termed a synodic revolution. This is longer than the 

 sidereal revolution, because the earth is also moving in the same direction 



43. 



FJ S- 567. Phases of the Moon. 



an~ the moon has to make up the time the earth has got on in front, as it 

 were. So the moon travels nearly thirteen times round the earth while the 

 latter is going round the sun. 



The revolutions of the moon have been a measurement of time for ages, 

 and her varying appearances during lunation are always observed with 

 interest. The illustration (fig. 567) will assist us materially. The sun's rays 

 fall in a parallel direction upon the earth and moon, and let us suppose 

 that s is the sun in the diagram and T the earth ; c at the various points is 

 the moon, the capital letters, A, B, c, etc., indicating the planet as she appears 

 from the sun, and the small letters show how she appears to us from the 

 earth. 



Let us suppose that the sun, earth, and moon are in conjunction or in 



