162 



A. M. W. DOWNING, M.A., D.SC, P.K.S., ON 



avoiding collision with vi. An inspection of the " General 

 Tables'' in the Prayer Book, especially of " Table III," with its 

 two horizontal lines allotted to each of the dates April 17 and 

 April 18, will show how these artifices are earned through the 

 calendar in the successive periods to which the tables apply. 



These regulations confine the dates of the Easter full moons 

 within the Paschal Limits, and ensure that Easter Day shall not 

 fall later thnn April 25. 



In the " Table of the Moveable Feasts for forty-six years "of 

 the Prayer Book will be found the values of the epacts for the 

 different years included in the table. Xo explanation of the 

 use of these epacts, as a means of determining the date of 

 Easter, is given in the Prayer Book, and in fact, no use is made 

 of them. A few words of explanation may, therefore, be 

 desirable, especially as it is recorded that Pope Gregory's 

 advisers arranged the lunar cycle by the epact. But when the 

 reformed calendar was adopted in England, Bradley preferred to 

 use the Golden Numbers as arranged in the Prayer Book, and 

 with which English-speaking people are, therefore, more 

 familiar. 



The epact, as now used in chronology, is simply the age of the 

 calendar moon on January 1 in each year of the nineteen-year 

 cycle. As twelve calendar lunations fall short by eleven days in 

 general of a mean solar year, the epacts for successive years are 

 formed as a rule by the addition of eleven to the value for the 

 preceding year. Just as the Golden Numbers have to be shifted 

 in position, so as to be affixed to different days in different 

 periods, so the epacts have to be adjusted to the nineteen-year 

 cycle, and to the Gregorian style, generally by the addition of a 

 unit at appropriate intervals. By this means the calendar 

 epacts are kept in harmony with the phases of the real moon. 

 During the period 1900 to 2199, the cycle of epacts is that 

 given in the Prayer Book table, referred to above, for the years 

 1900 to 1918 inclusive. When the addition of eleven to the 

 epact for any year produces a number greater than thirty, this 

 amount must be subtracted from the sum. Thus twenty-nine is 

 the epact for 1900, and this is followed by ten as the value for 

 1901. It will be noticed that seventeen is the epact for 1918, the 

 last year of the cycle, whilst that for the first year of the cycle is 

 twenty-nine, a difference of twelve. This is an instance of the 

 necessary readjustment of the epacts to which reference has been 

 made above. It will also be noticed that twenty-six is the epact 

 for 1916, following fourteen for 1915, and preceding six for 1917. 

 This substitution of twentv-six for twentv-five is an artifice 



