THE MOON 59 



began. It takes i8J years before she travels over the 

 same path a second time. 



3. That she travels in the same direction as the 

 sun and the chief planets. That direction is against 

 clock hands, contrary to the direction of rotation of 

 the star-sphere. 



4. That she completes her circle of the heavens in 

 27 days, 8 hours, or 27^ days. 



Since the Moon completes her round in 27 J days, 

 it would seem to follow that we shall have a new 

 Moon every 27j days. But this is not the case. 

 We have a new Moon only when the Moon is as 

 near as possible to the sun, on the same meridian 

 as the sun, and it takes more than 27^ days to 

 bring her round to that point. For during all the 

 time that the Moon is travelling round the ecliptic, the 

 sun is travelling too, and in the same direction, though 

 much slower. When the Moon has completed her 

 circle, she has still to go over the distance travelled 

 by the sun since the last new Moon. How much is 

 that ? The sun (apparently) travels round the heavens 

 in a year. He will, therefore, travel f -9 or about a 

 degree a day. That is about 28 in 28 days. At 

 the Moon's average rate of 12^ per day, it will take 

 her a little over two days to travel those 28, and to 

 overtake the sun, after she has completed her revolu- 

 tion round the earth. Hence the interval between 

 one new Moon and the next is 29! days, while the 

 revolution of the Moon round the earth occupies only 

 271 days. 



What is the figure of the Moon's path in space? 

 If we could look at the Moon from a very great 



