EASTER SUNDAY AND THE DOMINICAL LETTER. 9 



from the ist of January and after the so-called Intercalaiy 

 Date it is as if the year had begun one day later still in the 

 week. The whole line of days is shifted, as it were, one to 

 the left ; and each ^ day comes under the letter preceding the 

 one beneath which it had stood before — Sunday with the rest. 



12 3 4 5 6 7 



A B C D E F G 

 S mo tu we th fr sa 



It follows that Sunday, and with it of course the other days 

 of the week have for the rest of the year new letters, the ones 

 next preceding those which they had previous to the Intercal- 

 ary Day. A, therefore, as appears by the second little Table, 

 for Sunday. 



There are two Dominical Letters for each leap year, and 

 the intercalation throws the letter one place back. 



If, then, we know the Dominical Letter or Letters for any 

 3'ear, the framing of the " Block and Rhyme Device," set forth 

 later on in this paper, is a simple matter. 



The Dominical Letter for any year within reasonable limits 

 can be discovered by counting back or forward from any 

 known date. 



As the year goes forward the letter goes back, one place for 

 eveiy common year, two for eveiy leap year, the circle round. 

 As the year goes back the letter goes forward, one place for 

 every common year, two for every leap year, the circle round. 



But the Sunday Letter can be computed at once for any 

 year of the Gregorian Era by an arbitrar>' rule, and even 

 denoted by a general formula. 



I shall make an effort to set forth the results of that patient 

 thought which men, dead long ago, have in their time applied 

 to such a rule. 



