CHAPTER ELEVEN 



PHASES OF THE MOON AND ECLIPSES 



When, as the garish day is done, 

 Heaven burns with the descended sun, 



'Tis passing sweet to mark, 

 Amid that flush of crimson light, 

 The new moon's modest bow grow bright, 

 As earth and sky grow dark. 



BRYANT 



EVERY one must have noticed the moon's phases. 

 When people had no better light at night than moonlight, 

 they kept track of the moon from night to night more 

 closely than we are likely to do now. Can you tell 

 how often we have a new moon ? In what direction is it ? 

 Which way do the horns point? Did you ever see a 

 star between the horns ? It is remarkable that so many 

 intelligent persons have failed to understand the cause 

 of the moon's change in aspect. When once understood 

 the explanation is not likely to be forgotten. 



Why the moon seems to change its shape. The moon 

 shines only by reflected light; it is not self-luminous 

 like a ball of fire or a star. Place a light-colored ball 

 in the sunlight and view it from different positions. 

 You will see that the bright part may be a circle, a semi- 

 circle, a crescent, or some intermediate form, according 

 to your position. The part of the ball which is not 

 bright may show plainly without receiving light directly 

 from the sun, because various things around are reflect- 

 ing light to it. The moon out in space has nothing near 

 it to throw light upon it, and so only the part that receives 

 light directly from the sun is likely to be seen. If"you 

 are where you can see all the surface that is getting sun- 



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