lO BROWN : 



As to the formula, though it is entirely within the scope of 

 simple algebra, I shall not trouble 3'ou with it. 



In order to compute a letter it must be given a value in 

 numbers. In the present case A is the first letter, B the second 

 letter, and so on to G, the seventh letter. The letters are 

 made quantity by taking their ordinals. A ^ i, B = 2, and 

 so on in regular course. We thus start with A and from G. 

 And the calculation will bring out one of the first seven natu- 

 ral numbers, being devised to do so. 



With a view to the starting point it is natural to go back 

 to the beginning of the Christian Era. 



The year i of our era was historically the 753rd after the 

 foundation of Rome. It began on Saturday, January ist. Its 

 Sunday Letter was therefore B, and that of the year previous 

 was C. On this Basis (with a capital B) a computation can 

 be founded, and it is not difficult to remember that the year in 

 which the Birth (capital B) of our Lord is generally, but by 

 no means universally, regarded as having taken place had 

 for its letter, B. 



The letter backs one for evers' common year — two for eveiy 

 leap year. Leap years are ever\' fourth year, beginning with 

 the year One. It follows that if we add to the given date as 

 many whole fours as there are in the given date we shall have 

 a number of years in each of which the letter will back one. 

 Dividing now by seven, we shall have a number of cycles 

 which do not affect the result, and a remainder either of o, in 

 which case the letter is C, or else of some number less than 7, 

 in which case we back from C as many places as there are 

 units in the remainder. 



The letter found for leap year is for that part after the 29th 

 of Februaiy. The intercalary is regarded as already in its 

 place. The letter backs as the years advance, the former part 

 of the leap year is first reached and the latter part is crowded, 

 as it were, under a fresh letter one place farther back. 



The rule is general in the mathematical sense of the word ; 



