be able to expose them to view, folding doors were fixed on the front. The Liber Pontificalis states that St. 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 (see Altar-Steps). Originally it was made in the shape of an ordinary table, but gradually a step was introduced behind it and raised slightly above it (see Altar-Ledge). 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 (see Altar-Canopy), 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. (See Altar-Curtain.) The altar was often encircled by railings of wood, or metal, called cancelli, or by low walls of marble slabs called tranennæ. 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: (1) at each corner a column of natural stone, and the spaces between the columns may be filled with any kind of stone, brick, or cement; (2) the space between the two columns in front may be left open, so as to place beneath the table (exposed) a reliquary containing the body (or a portion of the body) of a saint; (3) besides the four columns, one at each corner, a fifth column may be placed in the centre at the front. In this case the back, and if desired the sides also, may be filled with stone, brick, or cement; (4) if the table is small (it should in every case be larger than the stone of a portable altar), four columns are placed under it, one at each corner and, to make up the full length required, frames of stone or other material may be added to each side. these added portions are not consecrated, and hence may be constructed after the ceremony of consecration; (5) if the table is deficient in width, four columns are placed under it, one at each corner, and a frame of stone or other material is added to the back. This addition is not consecrated, and may be constructed after the consecration of the altar. 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.
Altar-Candles.—For mystical reasons the Church prescribes that the candles used at Mass and at other liturgical functions be made of bees-wax (luminaria cerea.—Missale Rom., De Defectibus, X, I; Cong. Sac. Rites, 4 September, 1875). The pure wax extracted by bees from flowers symbolizes the pure flesh of Christ received from His Virgin Mother, the wick signifies the soul of Christ, and the flame represents His divinity. Although the two latter properties are found in all kinds of candles, the first is proper of bees-wax candles only. It is, however, not necessary that they be made of bees-wax without any admixture. The paschal candle and the two candles used at Mass should be made ex cerâ apum saltem in maximâ parte, but the other candles in majori vel notabili quantitate ex eadem cerâ (Cong. Sac. Rit., 14 December, 1904). As a rule they should be of white bleached wax, but at funerals, at the office of Tenebræ in Holy Week, and at the Mass of the Presanctified, on Good Friday, they should be of yellow unbleached wax (Caerem. Episc.). De Herdt (I, no 183, Resp. 2) says that unbleached wax candles should be used during Advent and Lent except on feasts, solemnities, and especially during the exposition and procession of the Blessed Sacrament. Candles made wholly of any other material, such as tallow (Cong. Sac. Rit., 10 December, 1857), stearine (Cong. Sac. Rit., 4 September, 1875), paraffin, etc., are forbidden. The Cong. Sac. Rit. (7 September, 1850) made an exception for the missionaries of Oceania, who, on account of the impossibility of obtaining wax candles, are allowed to use sperm-whale candles. Without an Apostolic indult it is not allowable, and it constitutes a grievous offense to celebrate Mass without any light (Cong. Sac. Rit., 7 September, 1850), even for the purpose of giving Holy Viaticum, or of enabling the people to comply with their duty of assisting at Mass on Sundays and holy days (St. Lig., bk. VI, n. 394). In these, and similar cases of necessity it is the common opinion that Mass may be celebrated with tallow candles or oil lamps (ibid.). It is not permitted to begin Mass before the candles are lighted, nor are they to be extinguished until the end of Mass. If the candles go out before the Consecration, and cannot be again lighted, most authors say that Mass should be discontinued; if this happens after the Consecration, Mass should not be interrupted, although some authors say that if they can possibly be lighted again within fifteen minutes the celebrant ought to interrupt Mass for this space of time (ibid.) If only one rubrical candle can be had, Mass may be celebrated even ex devotione (ibid).
