ID] MEMOIR EXPLANATORY OK \ NEW PERPETUAL CALENDAR. 



The whole system seemed to me "cycle and epicycle, orb in orb," the week appearing to 

 revolve about the letter A, and the year around the week. I had imagined the structure 

 of the Julian year, when once divested of the absurdity of calends, nones, and ides, (all 

 counted backwards,) and after having the week introduced, to be essentially simple; and 

 although the Dominical Letters, for ages consecrated to clerical use, had, I knew, been 

 adopted by the ablest astronomers and chronologists of modern times, and were still 

 employed conjointly with the golden number, by learned judges of the King's Bench, in 

 England, for ascertaining the legal periods of the four terms of court, yet I could not help 

 believing that some less circuitous method would sooner or later supersede an apparatus 

 which, however true in its results, and however lucid in comparison with some other 

 parts of the machinery, causes most persons, from its complexity alone, to consider even 

 the civil calendar a subject of much difficulty, and that of the Church as an impenetrable 

 mystery. I have, accordingly, always looked with particular interest at the Perpetual 

 Almanacs, so called, (but serving only for a single century,) which have since fallen in my 

 way, with a vague hope of being able to discover in them the germ of some simpler mode 

 of computation. 



On consulting, about two years ago, the seventh edition of the Encyclopedia Britan- 

 nica, I met accidentally with a new, well-digested, and perspicuous article on the "Calen- 

 dar," from the pen of Thomas Galloway, Esq., F. R.S., one of the Vice-presidents of the 

 Royal Astronomical Society, and was gratified at learning from it how much had been 

 done within the present half-century, by the analytical skill of Gauss and Delambre, 

 towards disencumbering the calendar of numerous tables, and substituting for them plainer 

 formula?. I perceived, however, and not without disappointment, that the Dominical Let- 

 ters were still retained among the elements of the algebraical equations, and on applying 

 them arithmetically I found my computation embarrassed at the outset by the quantity 

 7m joined with many quantities differing in sign, contained in the first equation, and at 

 the close, by another inconvenient equation,;? = P -j- (L — /,) involving the value not 

 only of the Sunday letter, but of a letter belonging to the fifteenth day of the calendar 

 moon. 



After a careful rcperusal of Mr. Galloway's essay, I was struck with the fact to which 

 I had never before adverted, that the first year of the Christian era began with Saturday, 

 which, being the seventh day of the week, and corresponding with seven, the number of 

 the hebdomadal cycle, suggested to me the possibility of making that number a convenient 

 starting-point of an indefinitely prolonged succession of ages or chronological periods, in 

 which the ordinal numbers appropriate to the other six days of the week, might perform 

 in a direct and more natural and intelligible manner, the same function that the Dominical 

 Letters, in a reversed order and in connexion with the Solar Cycle, had heretofore done. 

 Pursuing, as the amusement of many leisure hours, this casual thought, I have succeeded 

 in constructing what I believe to be a new instrument, of plain materials, but rather bet- 

 ter adapted than the old, for ordinary, popular use, and perhaps of a labour-saving cha- 

 racter, even in the hands of the learned; although to this last consideration I wish to be 

 understood as not attaching much importance, but merely as asking the opinion of 

 mathematicians in regard to the plan, if, at fir.-t blush, they should deem it at all worthy of 



