This use of relics is very ancient and can be traced back to the time of St Ambrose. There was also a custom, now obsolete, of enclosing a portion of the consecrated Eucharist if relics were not obtainable. This was ordered by cap. 2 of the council of Celchyth (Chelsea) in 816. But though ancient the custom of enclosing relics was not universal, and where found in English church orders, as it frequently is found from the pontifical of Egbert onwards, it is called the "Mos Romanus" as distinguished from the "Mos Anglicanus" (_Archaeologia_, liv. 416). It is absent from the description of the early Irish form of consecration preserved in the _Leabhar Breac_, translated and annotated by Rev. T. Olden in the _Transactions of the St Paul's Ecclesiolog. Soc._ vol. iv. pt. ii. p. 98.
The curious ritual act, technically known as the _abecedarium_, i.e. the tracing of the alphabet, sometimes in Latin characters, sometimes in Latin and Greek, sometimes, according to Menard, in Latin, Greek and Hebrew, along the limbs of St Andrew's cross on the floor of the church, can be traced back to the 8th century and may be earlier. Its origin and meaning are unknown. Of all explanations we like best the recent one suggested by Rossi and adopted by the bishop of Salisbury. This interprets the St Andrew's cross as the initial Greek letter of Christus, and the whole act as significant of taking possession of the site to be consecrated in the name of Christ, who is the Alpha and Omega, the word of God, combining in himself all letters that lie between them, every element of human speech. The three languages may then have been suggested by the Latin, Greek and Hebrew, in which his title was written on the cross.
The disentangling the Gallican from the Roman elements in the early Western forms of service is a delicate and difficult task, undertaken by Monsignor Louis Duchesne, who shows how the former partook of a funerary and the latter of a baptismal character (_Christian Worship_ (London, 1904), cap. xii.).
The dedication service of the Greek Church is likewise long and elaborate. Relics are to be prepared and guarded on the day previous in some neighbouring sacred building. On the morning following, all ornaments and requisites having been got ready, the laity being excluded, the bishop and clergy vested proceed to fix in its place and consecrate the altar, a long prayer of dedication being said, followed by a litany. The altar is then sprinkled with warm water, then with wine, then anointed with chrism in the form of a cross. The altar, the book of the gospels, and all cloths are then censed, every pillar is crossed with chrism, while various collects are said and psalms recited. One lamp is then filled with oil and lit, and placed on the altar, while clergy bring in other lamps and other ornaments of the church. On the next day--if the service cannot be concluded in one day--the bishop and clergy go to the building where the relics have been kept and guarded. A procession is formed and advances thence with the relics, which are borne by a priest in a holy vessel (_discus_) on his head; the church having been entered, the relics are placed by him with much ceremonial in the "confession," the recess prepared in or about the altar for their reception, which is then anointed and sealed up. After this the liturgy is celebrated both on the feast of dedication and on seven days afterwards.