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In the liturgy of the Roman Rite of the Catholic Church, the altar is the table on which the Sacrifice of the Mass is offered. Mass may sometimes be celebrated outside a sacred place, but traditionally never without an altar, or at least an altar stone until recent changes, a corporal now being sufficient.
In ecclesiastical history we find only two exceptions: St. Lucian (312) is said to have celebrated Mass on his breast whilst in prison, and Theodore, Bishop of Tyre on the hands of his deacons. According to Radulphus of Oxford (Prop. 25), Pope Sixtus II (257-259) was the first to prescribe that Mass should be celebrated on an altar, and the rubric of the missal (XX) is merely a new promulgation of the law. It signifies, according to Amalarius the Table of the Lord (mensa Domini), referring to the Last Supper, or the Cross, or Christ. The last meaning explains the honour paid to it by incensing it, and the five crosses engraved on it signify his five wounds.
In the earliest church buildings, the altar was situated in a way that the priest faced east during the prayers of the Eucharistic liturgy. Depending on the particulars of the specific church building in terms of space and orientation, this usually meant that the altar was placed at the east end, although there are also some notable exceptions, such as the Constantinian St. Peter's Basilica and St. Paul's Outside the Walls, wherein the altar was at the western end. This meant that in order for the celebrant to face true east during the Eucharistic prayers, he needed to stand on the western side of the freestanding altar and face towards the doors of the church. These are not, however, examples of ancient churches in which the priest or bishop celebrated the eucharist "towards the people," as congregations in these churches would stand in the side aisles, facing the altar during the scripture readings and homily but facing east along with the celebrant during the eucharistic prayer.
The basilicas of the Roman Empire were, as a rule, law courts or meeting places. They were generally spacious, and the interior area was separated by two or four rows of pillars, forming a central nave and side aisles. The end opposite the entrance had a semi-circular shape, called the apse, and in this portion, which was raised above the level of the floor, sat the judge and his assessors, and before them stood an altar upon which sacrifices were made before any public business was to begin.
When these public buildings were adapted for Christian assemblies, slight modifications were made. The apse was reserved for the bishop and his clergy; the faithful occupied the centre and side aisles, while between the clergy and people stood the altar. Later on the altar was placed in churches in the apse against, or at least near, the wall, so that the priest when celebrating faced the east, and behind him the people. In primitive times there was only one altar per church. Ignatius the Martyr, Cyprian, Irenaeus, and Jerome, speak of only one altar (Benedict XIV, De Sacr. Missae, no. 1, xvii). Some think that more than one altar existed in the Cathedral of Milan in the time of St. Ambrose, because he sometimes uses the word altaria, although others are of opinion that the word in this place means an altar.
There is evidence of a plurality of altars towards the end of the sixth century, for Gregory the Great sent relics for four altars to Palladius, Bishop of Saintes, France, who had placed in a church thirteen altars, four of which remained unconsecrated for want of relics. Although there was only one altar in each church, minor altars were erected in side chapels, which were distinct buildings (as is the custom in the Greek, and some Oriental Churches even at the present day) in which Mass was celebrated only once on the same day in each church (Benedict XIV, Ibidem). The fact that in the early ages of Christianity only the bishop celebrated Mass, assisted by his clergy, who received Holy Communion from the bishop's hands, is the reason that only one altar was erected in each church, but after the introduction of private Masses the necessity of several altars in each church arose.
In ceremonials there is mention of the right and left side of the altar. Before 1488, the epistle side was called the right side of the altar, and the gospel side the left. In that year, Augustine Patrizi, Bishop of Pienza, published a ceremonial in which the epistle side is called the left of the altar, and the gospel side the right, the denomination being taken from the facing of the crucifix, the principal ornament of the altar, not of the priest or the laity. This change of expression was accepted by Pope Pius V and introduced into the rubrics.
Although no documents are extant to indicate the material of which altars were made in the first centuries of Christianity, it is probable that they were made of wood, like that used by Christ at the Last Supper. At Rome such a wooden table is still preserved in the Lateran Basilica, and fragments of another such table are preserved in the church of Santa Pudenziana, on which St. Peter is said to have celebrated Mass.
During the persecutions, when the Christians were forced to move from one place to another, and Mass was celebrated in crypts, private houses, the open air, and catacombs, except when the arcosolia were used, it is natural to suppose that they were made of wood, probably wooden chests carried about by the bishops, on the lid of which Mass was celebrated. Optatus of Mileve (De Schismate Donatistarum) reproves the Donatists for breaking up and using for firewood the altars of the Catholic churches, and Augustine of Hippo (Epist. clxxxv) reports that Bishop Maximianus[disambiguation needed] was beaten with the wood of the altar under which he had taken refuge.
Gregory of Nyssa speaks of the consecration of an altar made of stone (De Christi Baptismate). Pulcheria, sister of Theodosius II, presented an altar of gold to the Basilica of Constantinople; St. Helena gave golden altars ornamented with precious stones to the church which was erected on the site where the Cross had been concealed for three hundred years; the Popes Sixtus III (432-440) and St. Hilary (461-468) presented several altars of silver to the churches of Rome. Since wood is subject to decay, the baser metals to corrosion, and the more precious metals were too expensive, stone became in course of time the ordinary material for an altar.
The Roman Breviary (9 November) asserts that St. Sylvester (314-335) was the first to issue a decree that the altar should be of stone. But of such a decree there is no documentary evidence, and no mention is made of it in canon law, in which so many other decrees of this Pope are inserted. Moreover, it is certain that after that date altars of wood and of metal were erected. The earliest decree of a council which prescribed that an altar which is to be consecrated should be of stone is that of the provincial council of Epeaune (Pamiers), France, in 517. The present discipline of the Church requires that for the consecration of an altar it must be of stone.
In primitive times there were two kinds of altars:
The Liber Pontificalis states that Pope Felix I decreed that Mass should be celebrated on the tombs of martyrs. This no doubt brought about both a change of form, from that of a simple table to that of a chest or tomb, and the rule that every altar must contain the relics of martyrs. Usually the altar was raised on steps, from which the bishop sometimes preached. Originally it was made in the shape of an ordinary table, but gradually a step was introduced behind it and raised slightly above it. When the tabernacle was introduced the number of these steps was increased. The altar is covered, at least in basilicas and also in large churches, by a canopy supported by columns, called the ciborium, upon which were placed, or from which were suspended, vases, crowns, baskets of silver, as decorations. From the middle of the ciborium, formerly, a gold or silver dove was suspended to serve as a pyx in which the Blessed Sacrament was reserved. Veils or curtains were attached to the columns which supported the ciborium. The altar was often encircled by railings of wood, or metal, called cancelli, or by low walls of marble slabs called tranennae.
According to the present discipline of the Church, there are two kinds of altars, the fixed and the portable. Both these denominations have a twofold meaning, i.e. an altar may be fixed or portable either in a wider sense or in the liturgical meaning. A fixed altar, in a wider sense, is one that is attached to a wall, a floor, or a column whether it be consecrated or not; in the liturgical sense it is a permanent structure of stone, consisting of a consecrated table and support, which must be built on a solid foundation. A portable altar in a wider sense is one that may be carried from one place to another in the liturgical sense it is a consecrated altar-stone, sufficiently large to hold the Sacred Host and the greater part of the base of the chalice. It is inserted in the table of an altar which is not a consecrated fixed altar.
The component parts of a fixed altar in the liturgical sense are the table (mensa), the support (stipes) and the sepulchrum. (See altar cavity.) The table must be a single slab of stone firmly joined by cement to the support, so that the table and support together make one piece. The surface of this table should be perfectly smooth and polished. Five Greek crosses are engraved on its surface, one at each of the four corners, about six inches from both edges. but directly above the support, and one in the centre. The support may be either a solid mass or it may consist of four or more columns. These must be of natural stone, firmly joined to the table. The substructure need not, however, consist of one piece, but should in every case be built on a solid foundation so as to make the structure permanent. The support may have any of the following forms:
In the last two cases the spaces between the columns may be filled with stone brick, or cement, or they may be left open. In every case the substructure may be a solid mass, or the interior may remain hollow, but this hollow space is not to be used as a closet for storing articles of any kind, even such as belong to the altar. Neither the rubrics nor the Sacred Congregation of Rites prescribe any dimensions for an altar. It ought, however, to be large enough to allow a priest conveniently to celebrate the Holy Sacrifice upon it in such a manner that all the ceremonies can be decorously observed. Hence altars at which solemn services are celebrated require to be of greater dimensions than other altars. From the words of the Pontifical we infer that the high altar must stand free on all sides (Pontifex circuit septies tabulam altaris), but the back part of smaller altars may be built against the wall.
In the beginning altars were not erected on steps. Those in the catacombs were constructed on the pavement, and in churches they were usually erected over the confession, or spot where the remains of martyrs were deposited. In the fourth century the altar was supported by one step above the floor of the sanctuary. At present the number of steps leading up to the high altar is for symbolical reasons uneven; usually three, five, or seven, including the upper platform (predella). These steps are to pass around the altar on three sides. They may be of wood, stone, or bricks, but St. Charles (Instructions on Ecclesiastical Building, xi, no. 2) would have the two or four lower steps of stone or bricks, whilst he prescribes that the predella, on which the celebrant stands, should be made of wood. The steps should be about one foot in breadth. The predella should extend along the front of the altar with a breadth of about three feet six inches, and at the sides of the altar about one foot. The height of each step ought to be about six inches. Side altars must have at least one step.
The sanctuary and altar-steps of the high altar are ordinarily to be covered with carpets. If the sanctuary floor be marble, tile, or tessellated woodwork, at least a broad strip of carpet should be placed before the lowest step in plano. On solemn feasts particularly, rugs of fine quality are reserved for the predella and altar-steps. If the whole sanctuary and altar-steps cannot be covered, at least the predella of the high altar, and of the other altars should have a rug (Caerem. Episc., I, xii, 16). Exceptions to this rule: (1) From the time of stripping the altars on Holy Thursday to Holy Saturday the carpets are removed. They are replaced on Holy Saturday before the Mass. (2) During solemn Requiem Masses the floor of the sanctuary and the altar-steps are to be bare although a suitable rug may be placed on the predella and, when a bishop celebrates, in front of the faldstool (Caerem. Episc., II, xi, 1). The same authority mentions that the carpet should be of green colour, but any may be used. Care should be taken that crosses, images of the saints, emblems, e.g. chalice, lamb, etc., and monograms of the Holy Names, etc., be not woven into the carpets, for it is unbecoming and unseemly that the figures of sacred things be trodden upon. These remarks apply equally to marble, tile, mosaic, etc., floors.
The "Caeremoniale Episcoporum (I, xii, 13), treating of the ornaments of the altar, says that a canopy (baldachinum) should be suspended over the altar. It should be square in form, sufficiently large to cover the altar and the predella on which the celebrant stands, and if it can easily be done, the colour of the material, silk velvet or other cloth, with which it is covered, should vary with the colour of the ornaments of the altar. It is either suspended from the ceiling by a movable chain, so that it may be lowered or raised when necessary, or it may be attached to the wall, or to the reredos at the back of the altar. It may also be a stationary structure, and this is usually the case in large churches, and then it is made of marble, stone, metal, or wood beautifully carved and overlaid with gold or silver, in the form of a cupola erected on four pillars. In liturgy it is called the ciborium. The canopy or ciborium is, according to the decision of the Cong. Sac. Rit., to be erected over the altar of the Blessed Sacrament (23 May 1846), and over the other altars of the church (27 April 1697), but as contrary custom has so far prevailed that even in Rome it is usually erected only over the high altar, and the altar of the Blessed Sacrament.
The purpose of this canopy is to protect the altar from dust or other matter falling upon it from the ceiling. A temporary canopy is sometimes placed over an altar in or outside the church. The framework on which such a canopy is erected is called the "altar-herse".
Formerly, between the columns of the ciborium ran metal rods, holding rings to which were fastened curtains which according to the rubrics of the individual churches, were drawn around the altar at certain parts of Mass. These curtains were styled tetravela altaris. When the ciboria over the altar fell into disuse a curtain was suspended at the back of the altar, called a dossel, or dorsal, and two others, one at each side of it. They were hung to rods fastened in the wall or reredos, or rested on four pillars erected at each end of the altar. The pillars were surmounted by angels holding candelabra, in which candles were burnt on solemn occasions.
Originally the altar was made in the shape of an ordinary table, on which the crucifix and candlesticks were placed. By degrees, behind the altar a step was introduced, raised slightly above it, for candlesticks, flowers, reliquaries, and other ornaments. This step was called the altar-ledge. Later the tabernacle was added as a stationary appends of the altar and at its sides and behind it other steps were placed. They are sometimes called degrees or gradini. The front of these steps was sometimes painted and decorated; the gradini of Brunelleschi's church of Santo Spirito, Florence, display groups of subjects from the Passion of Christ.
From at least the 4th to the Late Middle Ages the altar was covered from the view of the congregation at points during the mass by altar curtains hanging from rods supported by a ciborium, "riddel posts", or some other arrangement (as is still done in both the Orthodox Armenian Apostolic Church and Catholic Armenian Catholic Church). This practice declined as the introduction of other structures that screened the altar, such as the iconostasis in the East and rood screen and pulpitum in the West, meant that the congregation could barely see the altar anyway.
The altar frontal (Antependium, pallium altaris) is an appendage which covers the entire front of the altar, from the lower part of the table (mensa) to the predella, and from the gospel corner to that of the epistle side. Its origin may probably be traced to the curtains or veils of silk, or of other precious material, which hung over the open space under the altar, to preserve the shrines of the saints usually deposited there. Later, these curtains were converted into one piece of drapery which covered the whole front of the altar and was suspended from the table of the altar.
The use of a frontal which covers only a small portion of the front of the altar is forbidden. If the altar is so placed that its back can be seen by the people, that part should likewise be covered with an antipendium. Its material is not prescribed by the rubrics. It is sometimes made of precious metals, adorned with enamels and jewels, of wood, painted, gilt, embossed, and often set with crystals or of cloth of gold, velvet, or silk embroidered and occasionally enriched with pearls, but it is usually of the same material as that of the sacred vestments. It is evidently intended as an ornament of the altar. Hence if the altar is made of wood or marble, and its front is beautifully painted or decorated, or if the table is supported by columns, and a reliquary is placed under it, it may be considered sufficiently ornamented, and the antipendium would not be necessary; nevertheless, even in such cases, on solemn occasions more precious and elaborate ones should be used. The antipendium may be ornamented with images: pictures of Christ, or pictures of the saint in whose honour the altar is dedicated to God, and emblems referring to such saint, may be used. It is forbidden to ornament the black antipendium with skulls, cross-bones, etc.
Regularly, the colour of the antipendium should correspond with the colour of the feast or office of the day. The Missal says this should be the case quoad fieri potest, by which the Missal does not imply that one colour may be used ad libitum for another, but that the more precious antipendia of gold, silver, embroidered silk, etc., in colours not strictly liturgical, may be used on solemn occasions, although they do not correspond in colour with the feast or office of the day. The following are exceptions to the general rule: (1) When the Blessed Sacrament is publicly exposed the antipendium must be white, whatever the colour of the vestments may be. If, however, the Exposition takes place immediately after Mass, or Vespers, the antipendium of the colour of the Mass, or Vespers, may be retained if the celebrant does not leave the sanctuary between the Mass, or Vespers, and the Exposition; but if on these occasions he vests for the exposition outside the sanctuary, the antipendium if not white must be exchanged for a white one. (2) In solemn votive Masses the colour of the antipendium must be that of the vestments. In private votive Masses (missae lectae) its colour corresponds to that of the office of the day. In private votive Masses celebrated solemnly, i.e. with deacon and subdeacon, or in chant (missae cantatae) it is proper that its colour correspond with that of the vestments.
The altar protector is a cover made of cloth, baize or velvet which is placed on the table of the altar, during the time in which the sacred functions do not take place. Its purpose is to prevent the altar-cloth from being stained or soiled. It should be a little wider than the table and somewhat longer than the latter, so that it may hang down several inches on each side and in front. It may be of any colour (green or red would seem to be the preferred colours), and its front and side edges are usually scalloped, embroidered, or ornamented with fringes. During the divine services it is removed, except at Vespers, when, during the incensing of the altar at the Magnificat, only the front part of the table need be uncovered, and it is then simply turned back on the table of the altar. It is called the vesperale, the stragulum or altar-cover. It need not be blessed.
An altar candlestick consists of five parts: the foot, the stem, the knob about the middle of the stem, the bowl to receive the drippings of wax, and the pricket, i.e. the sharp point that terminates the stem on which the candle is fixed. Instead of fixing the candle on the pricket, it is permissible to use a tube in which is put a small candle which is forced to the top of the tube by a spring placed within.
In the early days of the Church candlesticks were not placed on the altar though lights were used in the church, and especially near the altar. The chandeliers were either suspended from the ceiling or attached to the side walls, or were placed on Pedestals. When the chandeliers were fed with oil they were usually called canthari, when they held candles they went by the name of phari, although frequently these words were applied indiscriminately to either. The lights usually assumed the form of a crown, a cross, a tree, etc., but at times also of real or imaginary animals. We have no documentary evidence that candlesticks were placed on the altar during the celebration of the Holy Sacrifice before the tenth century. Pope Leo IV (847-855) declared that only the relics of saints and the book of the Gospels might be placed on the altar. No writer before the tenth century who treats of the altar makes mention of candlesticks on the altar, but mention is made of acolytes carrying candlesticks, which, however, were placed on the floor of the sanctuary or near the corners of the altar, as is still the custom in the Eastern Church. Probably in the twelfth century, and certainly in the thirteenth, lights were placed on the altar; for Durandus says "that at both corners of the altar a candlestick is placed to signify the joy of two Peoples who rejoiced at the birth of Christ", and "the cross is placed on the altar between two candlesticks."
The custom of placing candlesticks and candles on the altar became general in the sixteenth century. Down to that time only two were ordinarily used, but on solemn feasts four or six. At present more are used, but the rubric of the missal (20) prescribes only two, one at each side of the cross, at least at a low Mass. These candlesticks and their candles must be placed on the altar, their place cannot be taken by two brackets attached to the superstructural steps of the altar, or affixed to the wall. According to the Caeremoniale Episcoporum, there should be on the high altar six candlesticks and candles of various sizes, the highest of which should be near the cross. If all six be of the same size they may be placed on different elevations, so as to produce the same effect; a custom, however, has been introduced of having them at the same height and this is now permissible. On the other altars of the church there should be at least two candlesticks, but usually four are used; on the altar of the Blessed Sacrament, if the Blessed Sacrament is not kept on the high altar, there should regularly be six. The Roman Missal says also that a third candlestick and candle should be placed at the epistle side, and that this extra candle should be lighted at low Masses from the consecration to the consumption of the Precious Blood. This rubric is only directive. The third light is not placed on the altar itself, but on the credence, or on the step of the altar at the place where the altar-boy kneels. A bracket affixed to the wall may be used for this candlestick. The candlesticks may be made of any kind of metal or even of wood, gilded or silvered, but on Good Friday silvered ones may not be used. The candlesticks destined for the ornamentation of the altar are not to be used around the bier at funerals, or around the catafalque at the commemoration of the dead, during Mass or other functions, at least on solemn feasts, they cannot be covered with a cloth or veil. Candelabra holding several candles cannot be used for the candlesticks prescribed by the Rubrics.
The Cæremoniale Episcoporum says that between the candlesticks on the altar may be placed natural or artificial flowers, in an altar vase. Lanterns are used in churches to protect the altar candles and lamp. They are of perforated metal-work or set with crystals.
The chalice is the cup in which the communion wine and is contained. It should be either of gold, or of silver with the cup gilt on the inside or it may have a cup only of silver, gilt on the inside; in which case the base and stem may be of any metal, provided it be solid, clean, and becoming. According to the Roman Missal it may be also made of stannum. Chalices made of glass, wood, copper, or brass are not permitted, and cannot be consecrated by the bishop. The base may be round, hexagonal, or octagonal, and should be so wide that there is no fear of the chalice tilting over. Near the middle of the stem, between the base and the cup, there should be a knob, in order that the chalice may be easily handled; this knob may be adorned with precious stones. The base and cup may be embellished with pictures or emblems, even in relief, but those on the cup should be about an inch below the lip of the chalice. The cup should be narrow at the bottom, and become gradually wider as it approaches the mouth. The height is not determined, but it should be at least eight inches.
The paten is a vessel of the Altar on which the Eucharistic Bread is placed. It should be made of the same material as the chalice, and if it is made of anything else than gold it should be gilt on the concave side. Its edge ought to be thin and sharp, so that the particles on the corporal may be easily collected. It should not be embellished, at least on the concave side, in any manner; however, one small cross may be set near its edge to indicate the place on which it is to be kissed by the celebrant. Pope Pius IX allowed chalices and patens to be used which were made of aluminium mixed with other metals in certain proportions given in the "Instructio", provided the whole surface was silvered, and the cup gilt on the inside, but this decree was later expunged from the Decrees.
Both the chalice and the paten, before they can be used for the Holy Sacrifice of the Mass, must be consecrated by the ordinary, or by a bishop designated by him.
The ciborium is an altar-vessel in which the consecrated particles for the Communion of the laity are kept. It need not necessarily be made of gold or silver, since the Roman Ritual (tit. cap. i, n. 5) merely prescribes that it be made ex solida decentique materia. It may even be made of copper provided it be gilt (Cong. Sac. Rit., 31 August 1867). If made of any material other than gold, the inside of the cup must be gilt (Cong. Episc. et Reg., 26 July 1588). It must not be made of ivory (ibid.) or glass (Cong. Sac. Rit., 30 January 1880). Its base should be wide. its stem should have a knob, and it may be embellished and adorned like the chalice. The cover, which should fit tightly, may be of pyramidal or a ball shape, and should be surmounted by a cross. The ciborium ought to be at least seven inches high. It is not consecrated, but only blessed by the bishop or priest having the requisite faculties according to the form of the "Benedictio tabernaculi" (Rit. Rom., tit. iii, xxiii). As long as the Blessed Sacrament is reserved in it, the ciborium must be covered with a veil of precious material of white colour (Rit. Rom., tit. iv, 1, n. 5), which may be embroidered in gold and silver and have fringes about the edges. When it does not actually contain the Blessed Sacrament, this veil must be removed. Hence, after its purification at Mass, or when filled with new particles to be consecrated, it is placed on the altar, the veil cannot be put on it. Even from the Consecration to the Communion it remains covered. Just before placing it in the tabernacle after Communion the veil is placed on it. It is advisable to have two ciboria as the newly consecrated particles must never be mixed with those which were consecrated before. In places in which Holy Communion is carried solemnly to the sick, a smaller ciborium of the same style is used for this purpose. The little pyx used for carrying Holy Communion to the sick is made of the same material as that of which the ciborium is made. It must be gilt on the inside, the lower part should have a slight elevation in the centre, and it is blessed by the form "Benedictio tabernaculi" (Rit. Rom., tit. viii, xxiii).
The ostensorium (ostensory, monstrance) is a glass-framed shrine in which the Blessed Sacrament is publicly exposed. It may be of gold, silver, brass, or copper gilt (Cong. Sac. Rit., 31 August 1867). The most appropriate form is that of the sun emitting its rays to all sides (Instructio Clement., 5). The base should be wide, and at a short distance above it there should be a knob for greater ease in handling. The ostensorium must be surmounted by a cross. (Cong. Sac. Rit., 11 September 1847). It should not be embellished with small statues of saints, as these and the relics of saints are forbidden to be placed on the altar during solemn Benediction. At the sides of the receptacle in which the lunula is placed it is appropriate to have two statues representing adoring angels. In the middle of the Ostensorium here should be a receptacle of such a size that a large Host may be easily put into it; care must be taken that the Host does not touch the sides of this receptacle. On the front and back of this receptacle there should be a crystal, the one on the back opening like a door, when closed, the latter must fit tightly. The circumference of this receptacle must either be of gold or, if of other material, it should be gilt and so smooth and polished that any particle that may fall from the Host will be easily detected and removed. The lunula must be inserted and recovered without difficulty, hence the need for keeping it in an upright position should be construed with this end in view. The ostensorium need not necessarily be blessed, but it is better that it should be. The form "Benedictio tabernaculi" (Rit. Rom., tit. viii, xxiii) or the form "Benedictio ostensorii" (Rit. Rom., in Appendice) may be used. When carried to and from the altar it ought to be covered with a white veil.
The lunula (lunette) is made of the same material as the ostensorium. If it be made of any material other than gold, it must be gilded (Cong. Sac. Rit., 31 August 1867). In form it may be either of two crescents or of two crystals encased in metal. If two crescents be used, the arrangement should be such that they can be separated and cleaned. Two stationary crescents, between which the Sacred Host is pressed, are, for obvious reasons, not serviceable. If two crystals are used it is necessary that they be so arranged that the Sacred Host does not in any way touch the glass (Cong. Sac. Rit., 14 January 1898). The ostensorium, provided it contains the Blessed Sacrament, may be placed in the tabernacle, but then it should be covered with a white silk veil.
Altar breadboxes are made of wood, tin, britannia metal, silver, or other metal. In order that the breads may not become bent or curved, a round flat weight, covered if necessary with silk or linen, and having a knob on top, so as to be easily taken hold of, is placed on the breads.
The altar cavity is a small square or oblong chamber in the body of the altar. This cavity is called, in the language of the Church, the sepulchrum.
In it are placed, according to the Pontificale Romanum (De Eccles. Consecratione) the relics of two canonized martyrs, although the Cong. Sac. Rit. (16 February 1906) decided that if the relic of only one martyr is placed in it the consecration is valid, to these may be properly added the relics of other saints, especially of those in whose honour the church of the altar is consecrated. These relics must be actual portions of the saints' bodies, not simply of their garments or of other objects which they may have used or touched; the relics must, moreover be authenticated.
If the altar is a fixed or immovable altar, the relics are placed in a reliquary of lead, silver, or gold, which should be large enough to contain, besides the relics, three grains of incense and a small piece of parchment on which is written an attest of the consecration. This parchment is usually enclosed in a crystal vessel or small vial, to prevent its decomposition. The size of the cavity varies to suit the size of the reliquary. If it is a portable altar the relics and the grains of incense are placed immediately, i.e. without a reliquary, into the cavity. This cavity must be hewn in the natural stone of the altar. Hence, unless the altar be a single block of stone, a block of natural stone is inserted for the purpose in the support. The location of the cavity in a fixed altar is
If the first or the second location is selected, a slab or cover of stone, to fit exactly upon the opening, and for this reason somewhat bevelled at the corners, must be provided. The cover should have a cross engraved on the upper and nether sides. If the third location is chosen the table (mensa) itself serves as the cover. In a portable altar the cavity is usually made on the top of the stone near the front edge, although it may be made in the centre of the stone.