Previously Unpublished Works, Fascicles VI-VII

The number of computists computists Scholars who specialized in the "computus," the science of calculating calendar dates, especially the date of Easter. of this period testify to the general interest in the subject. Thurkil (see Haskins, p. 330) and Nebroz (Haskins, p. 336) are frequently quoted by Philip de Thaun, who wrote in Anglo-Norman ‘of the calculation’ original: "di cumpaz" circ. 1119 A. D., printed by Thomas Wright in 1841 and Ed. Mall in 1873. The number of tracts going over the same ground and containing nothing new written during the first two-thirds of the twelfth century is extremely large.

THE FAULTS OF THE CALENDAR.

Even in the eleventh century it was noticed that the calendar was inaccurate. A chronicler notes in 1082 A. D. that the Paschal Relating to Easter. new moon was falsely predicted, and later on, the defects of the epact epact The number of days by which the solar year exceeds the lunar year, used to determine the moon's age on a specific date. as a means of finding the age of the moon became apparent. It is not, however, till the middle of the twelfth century that we find any trace of an inquiry into the reason of the error, which arose from the wrong length of a lunar month assumed by the calendar. It is fairly obvious that the mere presence of a Jewish community, however small, would call attention to the greater accuracy of their tables for calculating the new moon, and as nearly all early treatises call attention to the Jewish determinations as well as those of the Chaldeans and of the Arabs, we may fairly attribute to Jewish learning some share of the introduction of astronomical considerations into calendar reform.

The first result of this is seen in the treatise of Roger of Hereford, On Calculation original: "De Computo", found in a Bodleian manuscript, Digby 40, ff. 21–50 v., written 1176 A. D. The author does not know the correct length of the year, but calculates the length of a mean lunar month from the eclipse noted by Gerland and from one of his own time, and points out that by the calendar there should be a new moon on Thursday, September 9. By the ‘natural calculation’ original: "naturalis compotus"; referring to calculations based on observed astronomical phenomena rather than the fixed rules of the Church calendar. it should be on the 6th hour of the night preceding Monday, September 6; according to the Hebrews on the 24th hour of Sunday, September 5; according to the Chaldeans on the 17th hour of Sunday; according to the Astrologers (astronomers) the 22nd hour of Sunday—two hours before midnight; he himself put it at the hour before sunrise on Sunday; our tables give the conjunction The moment when the moon and sun are at the same celestial longitude; the astronomical new moon. as 1 a.m. on September 5. Roger quotes from no Arabic source, except from ‘Abumaisar’ Abu Ma'shar, a famous Persian astrologer and astronomer (787–886 A.D.) whose works were influential in medieval Europe. for the causes of spring and neap tides, rejecting his explanation as unnecessary. We first meet in this treatise the objection to altering the calendar on the ground of obedience to the Nicene Council The Council of Nicaea (325 A.D.), which established the initial rules for calculating Easter.:—‘nor [does] it itself (that is, the common [calendar]... original: "nec ipsum (i. e. vul-"; the sentence is interrupted by the page break and likely refers to the "vulgatus" or common ecclesiastical calendar.