The rules laid down in the general rubrics of the Breviary for commemorations were never very simple, and when we read the changes brought about in De ratione Divini officii recitandi juxta novum Psalteri ordinem, Titles II., III., IV., V., VI., with' the decrees of the Congregation (January, 1912), and subsequently (Abhinc duos Annos) everyone must fear to tread the maze with certainty and must often fall back gratefully on the labours of the compilers of the Ordo which he follows. Or, perhaps, doubts may be dispelled by The New Psalter (Burton and Myers) published in 1912. The chapter on the Calendar in that book is worth study, but needs now additions and corrections, owing to the issue of more recent decrees.

In the study of commemorations and translations of feasts there are two words which have a special meaning and which, being often used in calendar working, deserve a special note. They are "occurrence" and "concurrence." Occurrence is the conjunction of two or more offices, which fall on the same day. It may be accidental when two movable feasts are concerned or when a movable feast falls on a day which has a fixed office; or it may be perpetual, when a fixed office falls on a day which already has a fixed office. The Church does not ask the recitation of a double or a triple office. She, by her fixed rules, prefers one out of the two of the "occurring" offices, transfers if possible the others, or at least commemorates them by an antiphon, versicle and prayer, and sometimes by a ninth lesson at Matins.

Concurrence is the conjunction of two offices, which succeed one another, so that a question arises as to which feast the Vespers belong to; whether to the feast of the day or to the feast of the following day, or whether the psalms should be of the feast and the remaining part of the Vespers should be as the Ordo so often notes (a cap. de seq.), from the capitulum the office is taken from the following feast.

The new rubrics contain five titles which make certain modifications in the rules hitherto observed. We thus obtain a ready made division of the subject:—

(1) Of the precedence of Feasts (Title II.). (2) Of the accidental occurrence of feasts and their translation (Title III.). (3) Of the perpetual occurrence of feasts and their transfer (Title V.). (4) Of the occurrence of feasts (Title V.). (5) Of the commemorations (Title VI.) (Myers and Burton, op. cit.).

The new rubrics without the aid of any commentator give pretty clear notions of the laws of precedence, occurrence and commemoration. For students in college these rules are expounded in detail with additions, changes, exceptions. But for priests, long past the student stage, it is difficult to undo the fixed liturgy lore of their student and early priest life; and the need of such a book as The New Psalter and its Uses is, for those interested, a necessity. Even since the publication of that book, changes have been made. For example, doubles, major or minor and semi-doubles, which were perpetually excluded on their own day were transferred to some fixed day. This is given in The New Psalter and its Uses. But this has now been changed. In the case of feasts of the universal Church, no translation is allowed now. But feasts proper to a nation, diocese, order, institute or particular church may still be transferred to a fixed day, if perpetually impeded on their own day. Another example of necessary changes in that excellent book is in the last paragraph of page 136 (see Decree S.C.R., June, 1912). The works of compilers and liturgists need constant revision to keep pace with new decisions and decrees.

In making commemorations, the order of the commemoration as laid down in the Ordo should be followed. Elements of a commemoration are the Antiphon of the Benedictus or the Magnificat with versicle and response. These antiphons are considered most excellent, preceding as they do the Gospel canticles (St. Luke I.). The antiphon, versicle and prayer of the commemoration at an hour should never be repetitions of others said in the same hour. Thus, if in the office of a confessor pontiff having the prayer Da quaesumus, another confessor pontiff's feast, commemorated in the same hour, should not have the same prayer. About the prayer, or, as it is called, the collect, the following should be noted: first, the commemoration is omitted if the prayer of the office which is being recited and the prayer of the feast to be commemorated have the same object. Thus, a feast of the Blessed Virgin, falling within the octave of the Assumption, should not be commemorated. Second, where a commemoration for a saint or saints of title similar to that of the saints whose office is being said, is to be made, the Congregation of Rites (5th May, 1736) arranged that not even the versicles and response be repeated and that the following order be observed:—

IN VESPERS—

1st Com. made by Antiphon and Versicle of Lauds. 2nd Com. made by Antiphon of second Vesper and Ver. of II. Nocturn. 3rd Com. made by Antiphon of I. Noct. and Vers. of III. Nocturn.

IN LAUDS—

1st Com. made by Antiphon and Vers. from first Vesp. 2nd Com. made by Antiphon I. Noct., and Ver., III. Noct. 3rd Com. made by Antiphon II. Vesp., Vers., II. Noct.

If it should happen in commemorating a day within an octave that the versicle from the common had already been taken for the office, then the rule is "Sumenda est in laudibus antiphona de secundis Vesperis; et pro secundis Vesperis antiphona de laudibus in utroque tamen casu cum v. de primis Vesperis" (S.C.R., 18th Dec., 1779). In the above given form of making commemorations it may be noted that the second commemoration in Lauds is made up from the versicles and response of Matins and not from second Vespers, so as to avoid repeating in Lauds what was said at Vespers (Cavalieri).

As regards prayers in the office the reminder that the same formula must not be repeated in the same hour may be supplemented. Because, prayers having all words identical, save one single word, are not considered in liturgy as different prayers (e.g., Accendamur exemplis; instruamur exemplis, Feast of St. Philip and St. James, Feasts of several martyrs). So, too, prayers which have the same form of petition (e.g., the prayers on feast of St. Joseph and on feast of St. Mathew), are not considered as different and must not be repeated in the same hour. But where the petition is different, even though all the remainder of the prayers are similar in wording, they may be repeated in the same hour.

But what is to be done in offices where a commemoration prayer and the prayer of the office is from the common? What must be done where the feast is the feast of a Doctor and a commemoration of a Doctor is to be made? What is to be done when the office of the feast is of a virgin not a martyr, and a commemoration of a virgin not a martyr is to be made? In the first case the prayer from the office of a confessor or Pontiff should be said, adding to it the title of Doctor. In the other case, the prayer Indulgentiam, omitting the word martyr, is to be said.

The origin of these commemorations was, that the Popes in removing the solemn celebrations of certain feasts of Apostles and Martyrs, which were formerly of precept, provided that their cultus should not be forgotten, and that their commemoration in the office should remind priests and the faithful of those servants of God, whom the Church wishes ever to honour. I have said the order given for commemoration in the Ordo should be followed; but not to follow this order does not exceed a venial sin. Even the deliberate omission of a commemoration in Lauds or Vespers is not a violation of a grave precept.