NOTES AND QUERIES. [9* h s. XL MARCH 7, i9os.
EASTER DAY AND THE FULL MOON.
(See ante, pp. 67, 117.)
THE Prayer Book rule for keeping Easter is that " Easter-Day is always the First Sunday after the Full Moon which happens upon or next after the Twenty-first Day of March with the surely superfluous addition, and it the Full Moon happens upon a Sunday, Faster- Day is the Sunday after." Occasionally, how- ever, as in the present year, our almanacs give Easter Day on the actual day of the full moon, which seems to the ordinary mind to be in contradiction to the rule, and generally leads some persons to fancy that a mistake has been committed. Thus the moon will this year be full at eighteen minutes past midnight (by Greenwich time) on 11 April, or eighteen minutes after the beginning of 12 April by civil reckoning. That day is, however, Easter Day in accordance with the calendar rules, which are given in the Prayer Book under the heading 'Table to find Easter from the Year 1900 to the Year 2199 inclusive.' It will there be seen that, the Golden Number this year being IV., the Pas- chal full moon (set down in the second column) is 11 April, and the next day, being Sunday, is Easter Day. The Paschal or eccle- siastical full moon, then, does not necessarily (though the exceptions are rare) correspond with the day of full moon at any particular place. It cannot do so at all places because the times of full moon are not the same in different longitudes, so that it would be im- possible to regulate Easter by the actual or astronomical full moon. Thus on the present occasion the moon will be full after midnight on 11 April (so that, by civil reckoning, it will be after 12 April has begun) at Green- wich, but before midnight in all places more than 4 degrees to the west of Greenwich, which includes all Ireland and the county of Cornwall, all Portugal, and the western half of Spain.
To find the Golden Number for any year it is convenient to remember that every year divisible by nineteen without remainder has I. for its Golden Number, and for this century and next in all such years the Paschal full moon is on 14 April. As a period of nineteen years corresponds to one of two hundred and thirty-five lunations within about two hours, this correspondence lasts for two centuries. A shift, it will be noticed, was made in 1900, and before that, as an earlier table in the Prayer Book shows, the Paschal full moon corresponding to Golden Number I. was 13 April, whereas (as already remarked) it is now 14 April. For Golden Number II. it is
now 3 April, and for Golden Number III. (that for last year) it was 23 March. That day being Sunday, Easter Day was kept the Sunday after, on 30 March. This year, as before remarked, the Golden Number is IV., and the Paschal full moon by the calendar is 11 April, which being a Saturday, Easter Day is 12 April, the day of actual full moon to places east of 4^ degrees of west longitude from Greenwich, but the day after full moon to places west of that longitude.
This determination of the date of Easter by a set of rules and tables is not the same in the Anglican as in the Roman Church, but produces the same result by a simpler process, needing only the Golden Numbers and Sun- day Letters, without the epacts (or days of moon's age at the beginning of the year) which were formerly used. Our rules were established at the reformation of the calendar in 1752; and the Earl of Macclesfield, to whom the change was especially due, thus bringing our practice into conformity with that on the Continent, availed himself of the assistance of Dr. Bradley, then Astronomer Royal. But it may be noted that these rules cannot avoid what the early Church seems to have been anxious to avoid, keeping Easter on the day of the Jewish Passover, and it does so fall this year. How much better it would be if the Christian Church could agree to keep Easter on the first or second Sunday in April ! The latter would be preferable, because 9 April was probably the date of the first Easter.
W. T. LYNN.
CONVIVIAL CLUBS AND SOCIETIES.
(See 'Bucks and Good Fellows,' 9 th S. iv. 520:
vi. 213 ; viii. 479 ; ix. 443 ; x. 322.)
THE Mathematical Society was first estab- lished at the "Monmouth's Head," in Mon- mouth Street, Spitalfields, in the year 1717, by Joseph Middleton. It was removed thence to the "White Horse," Wheeler Street, Spital- fields, in 1725 ; thence, again, to the " Ben Jonson's Head," Spitalfields. In the year 1772 another Mathematical Society, then held at the " Black Swan," Brown's Lane, Spital- fields, was, at the request of its members (who brought with them their books, instru- ments, &c.), incorporated into this ; and f the year 1782 the society removed to tl " Black Swan." In 1783 the Historical Society, held at the "George," in Carter's Rents, Spitalfields, was (at the desire of its members, who brought their historical library with them) united to this society.
Modern Druids. See Heckethorn's ' Secret Societies,' vol. ii. p. 293.