DOME
, is a round, vaulted, or arched roof, of a church, hall, pavilion, vestibule, stair-case, &c, by way of crowning, or acroter.
DOMINICAL Letter, otherwise called the Sunday Letter, is one of these first seven letters of the alphabet ABCDEFG, used in almanacs &c, to mark or denote the Sundays throughout the year.
The reason for using seven letters, is because that is the number of days in a week; and the method of using them is this: the first letter A is set opposite the 1st day of the year, the 2d letter B opposite the 2d day of the year, the 3d letter C opposite the 3d day of the year, and so on through the seven letters; after which they are repeated over and over again, all the way to the end of the year, the letter A denoting the 8th day, the letter B the 9th, &c. Then whichever of the letters so placed, falls opposite the first Sunday in the year, the same letter, it is evident, will fall opposite every future Sunday throughout the year, because the number of the letters is the same as the number of days in the week, being both 7 in number; that is, in common years; for as to leap years, an interruption of the order takes place in them. For, on account of the intercalary day, either the letters must be thrust out of their places for the whole year afterwards, so as that the letter, for ex. which answers to the 1st of March, shall likewise answer to the 2d &c; or else the intercalary day must be denoted by the same letter as the preceding one. This latter expedient was judged the better, and accordingly all the Sundays in the year after the intercalary day have another Dominical letter.
The Dominical letters were introduced into the calendar by the primitive christians, instead of the nundinal letters in the Roman calendar; and in this manner were those seven letters set opposite the days of the year, to denote the days in the week, in most of our common almanacs, till the year 1771, when the initial letters of the days of the week were generally introduced instead of them, excepting the Sunday letter itself, which is still retained.
From the foregoing account it follows that,
1st, As the common year consists of 365 days, or 52 weeks, and one day over; the letters go one day backwards every common year: so that in such a year, if the beginning or first day fall on a Sunday, the next year it will fall on Saturday, the next on Friday, and so on. Consequently, if G be the Dominical letter for the present year, F will be that for the next year; and so on, in a retrograde order.
2d, As the bissextile or leap year consists of 366 days, or 52 weeks, and 2 days over, the beginning of the year next after bissextile goes back 2 days. Whence, if in the beginning of the bissextile year, the Dominical letter were G, that of the following year will be E.
3d, Since in leap-years the intercalary day falls on the 24th of February, in which case the 24th and 25th days are considered as one day, and denoted by the same letter; after the 24th day of February the Dominical letter goes back one place: thus, if in the beginning of the year the Dominical letter be G, it will afterwards change to the letter F for the remaining Sundays of the year. With us however, this day is now added at the end of February, and from thence it is that the change takes place.
4th, As every fourth year is bissextile, or leap-year, and as the number of letters is 7; the same order of Dominical letters only returns in 4 times 7, or 28 years; which without the interruption of bissextiles, would return in 7 years.
5th, Hence the invention of the solar cycle of 28 years; upon the expiration of which the Dominical letters are restored successively to the same days of the month, or the same order of the letters returns.
To find the Dominical Letter of any given year. Find the cycle of the sun for that year, as directed under cycle; and the Dominical letter is found corresponding to it. When there are two letters, the proposed year is bissextile; the former of them serving till the end of February, and the latter for the rest of the year.
The Dominical letter for any year of the present century may be found by this canon:
Divide the odd years, their fourth and 4, by 7,
What is left take from 7, the letter is given.
| Thus, for the year 1794, the odd years | 94 | |
| their 4th | 23 | |
| and | 4 | |
| divided by 7) | 121 | (17 |
| remains | 2 | |
| from | 7 | |
| leaves | 5 |
The Dominical letter may be found universally, for any year of any century, thus:
Divide the centuries by 4; and twice what does remain
Take from 6; and then add to the number you gain
Their odd years and their 4th; which dividing by 7,
What is left take from 7, the letter is given.
Thus, for the year 1878 the letter is F.
For the centuries 18 divided by 4, leave 2; the double of which taken from 6 leaves 2 again; to which add the odd years 78, and their 4th part 19, the sum 99 divided by 7 leaves 1; which taken from 7, leaves 6 answering to F the 6th letter in the alphabet.
By the reformation of the calendar under pope Gregory the 13th, the order of the Dominical letters was again disturbed in the Gregorian year; for the year | 1582, which had G for its Dominical letter at the beginning; by retrenching 10 days after the 4th of October, came to have C for its Dominical letter: by which means the Dominical letter of the ancient Julian calendar is 4 places before that of the Gregorian, the letter A in the former answering to D in the latter.
