LUNAR PHASES, 

 concave side of which is turned towards the west, and the 



Fig. 12. 



convex side towards the sun, as shown in fig. 13, the moon still 



Fig. 13. 



moving with the convex side of the crescent foremost. The 

 crescent becomes thinner and thinner as the moon approaches 

 the sun. 



During this progressive change the moon being west of the sun, 

 rises some time before it, and can be seen in the early morning, 

 until it approaches so near the sun and until the crescent becomes 

 so thin, that it is lost in the blaze of his splendour. The dark 

 hemisphere is then presented to the earth, and the moon is 

 invisible (fig. 14). 



Fig. 14. 



87. A column of the almanack is usually assigned to the " age 

 of the moon." The sense in which this term is used, however, 

 must not be confounded with that in which it is applied to the 

 ecclesiastical moon in the rules for ascertaining the date of 

 Easter. "We are here dealing not with the fictitious but with the 

 real moon ; and the age in question is the interval which elapses 

 between the moment of the last conjunction, and the moment at 

 which the age professes to be assigned. This interval is usually 

 given for the noon of each day, and is expressed in days and 

 tenths of a day, but with still greater precision for the principal 



E 2 51 



