EASTER SUNDAY AND THE DOMINICA!. LETTER. I3 



In the seventeen hundreds one letter or step back is can- 

 celled because 1700 is not a leap year. Add one, therefore, not 

 two, throw out the sevens and count back beginning with A. 



In the eighteen hundreds one more is cancelled — 1800 

 being a common year. Nothing, therefore, is to be added to 

 the year. 



In the nineteen hundreds still another year is cancelled. 

 This is subtracting one from the sum to be divided by seven, 

 and this, again, is the same as adding six, for the quotient 

 does not concern us. Add six, therefore, as being more con- 

 venient. 



The year 2000 being a leap year all remains as in the 

 nineteen hundreds, because no step back is cancelled. 



In the twenty-one hundreds one step back is cancelled, 

 because 2100 is a common year. Accordingly, instead of add- 

 ing six as in the year before, add but five. 



In the twenty-two hundreds, add four ; in the twenty-three 

 hundreds, three, and in the twenty-four hundreds three, again, 

 for the reasons given above. 



The twenty-four hundreds bring us round to the addition of 

 two, as in the sixteen hundreds. And so the process goes on, 

 ' ' in ssecula saeculorum. ' ' The Prayer Book rule is thus justified 

 and the table proved correct. 



It will be noticed that the columns go down by periods of 

 900 years. This is arithmetical necessity, the periods being 

 seven, and the included leap years, which cause no difference, 

 being two. 



The years between 1582 and 1600 come under the 1600 

 column for the reason that in them we back to A as starting- 

 letter, which is in fact increasing by two the sum of the years 

 to be divided into cycles of seven. 



For the years from the beginning of the era down to 1582 

 add one-quarter of the date to the date, omitting fractions. 

 Divide the sum by seven and with the remainder back from C, 

 as set forth previously. 



These two rules provide for any year in the Christian Era, 



