64 BROWN : 



of two diameters while she is wholly in a state of immersion. 



If the moon moved in the ecliptic she would come into 

 the earth's shadow once in every lunation, and would also 

 come directly between the sun and the earth once in every 

 lunation. 



She does not, however, move in the ecliptic, but is in it, 

 and below it, and above it at irregular intervals and at irreg- 

 ular distances. Sometimes, therefore, she avoids the shadow 

 altogether, sometimes she skirts it lightly, and sometimes 

 plunges wholly into it. 



It should be clear from the above that eclipses of the moon 

 are confined not only to the nodal epochs, but also to the 

 times of opposition. 



An eclipsed moon is always a full moon. 



It rarely happens more than twice in the j^ear that the 

 moon is at one and the same time in opposition and near her 

 node. Occasionally the unusual supervenes. In 1898, for 

 example, there were three eclipses of the moon — two partial 

 and one total. 



The moon is visible to a whole hemisphere (nearl)^ at one 

 time, and it is the hemisphere bounded by the line in which a 

 cone with apex at the moon is tangent to the earth. The 

 pole of this hemisphere will be a point somewhere on the par- 

 allel denoted by the moon's declination, and on the meridian 

 of the observer; in short, where the moon can be seen in the 

 zenith. This, as we already know, may be at any point 

 within a zone lying equally on both sides of the ecliptic and 

 10° 18' wide. 



Suppose, now, the moon in her node at the first of Cancer, 

 and full. This will place heron the meridian about midnight 

 of the December Solstice, and she will necessarily be totally 

 eclipsed. Her centre shall pass the axis of the shadow cone 

 at midnight precisely on the meridian of Greenwich. And 

 she will be 23° 30' north of the equator. 



Those living on the Tropic of Cancer will see her in the 

 zenith, and the hemisphere will, at the moment chosen, be 



