6 BROWN : 



of the moon at the beginning of the year i ) , and throwing out 

 the thirties we shall have the moon's age at the beginning of 

 that 3'ear. 



There are limitations to this rule of which due account is 

 taken. 



The difference between the moon's age at the end of the lunar 

 year and at the beginning of the solar j^ear is called the Epact. 



The same idea is conveyed by the ordinary definition, "The 

 moon's age on the first of January of the year in question." 



The age of the moon on the first of March, called the March 

 Epact, is the same as on the first of January, as will be evident 

 on counting days and finding two complete Julian lunations. 



And so another step is taken, for we have now the moon's 

 age on the 21st of March, and we can infer at once whether 

 the moon in question be the Paschal moon or not. If its age 

 be 14 days on the 21st of March, or if it be not 14 days old 

 until after the 21st of March, then the moon is the Paschal 

 moon according to the definition. If it be more than 14 days 

 old, or over the full on the 21st, then the next moon is the 

 Paschal moon and Easter is " late." There is a " long carni- 

 val," since Ash Wednesday depends upon Easter. 



We have now reached the number of days between the 21st 

 of March and the 15th of the Paschal moon, and in order to 

 have the Number of Direction, or the number of days between 

 the Paschal full moon and Easter Sunday it onh'' remains to 

 fix the day of the week on which the 21st of March must fall. 



This is provided for by a device called the Dominical Letter, 

 or letter that stands for Sunaay. 



The Dominical Letter is to be duly discussed within, and 

 may be taken for granted for the present. 



By its means the day of the week belonging to any date cf 

 the Christian Era may be determined. 



There has thus been sketched, as it were, the mathematical 

 machinery' by which Easter Sunday according to the decree of 

 the Council of Nice may be computed for any year of the 

 Christian Era. 



