COMPUTATION OF EASTER.

Marlborough Express, Volume IV, Issue 172, 24 April 1869, Page 3

COMPUTATION OF EASTER.

To the Editor of the Marlborough Express. Sik, A good deal of uneasiness appears to exist as to an alleged error in the celebration of Easter this year. At the beginning of the rules to know when the moveable feasts and holy days begin is the following : “Easter Day (on which the rest depend) is always the first Sunday after the full moon, which happens upon or next after the 21st day of March; and if the full moon happens upon a Sunday, Easter day is the Sunday after.” In the present instance in New Zealand the full moon occurred about nine in the morning of Sunday, the 28th March, and in a paragraph in the Wellington Independent it is urged that the 4th April, and not the Sunday before was Easter day. The paragraph begins with stating—“ A most extraordinary ecclesiastical mistake appears to have been made in the Southern hemisphere regarding Good Friday and Easter Day this year.” This is a confused way of stating the matter, as the alleged error depends not on latitude (north or south), but simply upon longitude. A little further examination will show that this difficulty applies, not particularly to the Southern hemisphere, but to all places between East Longitude 37 degs. and 180 degs. If in the week before Easter we had travelled eastwards a few degrees, so as to pass the meridian of 180 degs., we should have had to repeat one of the days of that week ; so that the full moon would have actually occurred to us on the Saturday , about half-past nine in the morning, that is to say-n-a day earlier by the calendar than to those situated to the west of that meridian. I n this year the full moon occurred on the Saturday evening, at 9‘32 by Greenwich time. At a meridian 37 degrees east of Geenwich the time would be 2 hours 28 minutes later when this same change took place, that is to say the moon would be full at midnight. If the full moon had fallen somewhat later iii the evening, say about a minute before midnight on the Saturday, at Greenwich, it would been full moon on the ’Sunday morning at Canterbury and Dover, and according to the argument of the writer iu the Independent, different Sundays should have been observed as Easter Day at Canterbury and Westminster. The same writer says—“ The mistabe arose from the date given in the calendar being accepted without its accuracy being tested by calculation ” It is not, however, a matter of accurate astro- ;; nomical calculation, but a question of law, and an examir ation of the tables and rules in the common prayer book will show that there is noroom for doubt or practical difficulty in the matter. It is clearly laid down that tne days to be reckoned as, the days of the paschal full moon are those days opposite which the golden number of the year is placed, aud plain technical rules are given for ascertaining the golden number aud dominical or Sunday letter for year. The golden number expresses the position of the

in a cycle of nineteen years, after which th® changes of the moon recur very nearly as befo u e. That these tables and rules aie not published with the idea of iheir being strictly accurate astronomically, in every extreme case, is shewn by the wording of the table for finding Easter from 1900 to 2199 inclusive, in which the words occur—“ in order that the ecclesiastical full moons may fall nearly on the same days with the real full moons, &c.” This clearly shows that for the purpose of calendar we are concerned only with the ecclesiastical full moons, by which perfect uniformity throughout the world is secured. At the same time these technical rules are so nearly correct that no actual discrepancy can occur sufficiently obvious to be determined without the aid of instruments. Alfred Dobson. Blenheim, April 22nd, 1869.