It was the first Council of Nice, in the year 325, that gave the dignity of canonical law to the custom of prayer on bended knees, and it is a surprising fact that none of the paintings of the Catacombs represent a devotee in the act of kneeling. We, however, know from the Acts of the Apostles that from the very first days of Christianity it was sometimes customary to kneel at prayer. As for the public prayers of the early Christians, the text of the principal ones has survived unaltered to our own days. As early as the close of the first century, the younger Pliny, writing to Trajan, told him that the Christians were accustomed to assemble at daybreak to sing a hymn in honour of Christ, whom they worshipped as God. This is a valuable piece of evidence, and it is moreover corroborated by the known custom that prevailed at the same epoch in the Church of Antioch, of celebrating the Holy Trinity (Figs. 160 and 161) by singing anthems, and of glorifying Christ, the Word of God, by the intoning of canticles and psalms. St. Irenæus, who wrote in the middle of the second century, also mentions in his work against heresy, a kind of _Gloria in excelsis_, which was chanted in Greek in Christian assemblies at the consecration of the host, and which may be translated thus: “To thee all glory, veneration, and thanksgiving; honour and worship to the Father, to the Son, and to the Holy Ghost, now and ever, and for century upon century of infinite eternity!” The people responded, “Amen!” In the dogmatic treatises written by Tertullian, at the end of the second century, that great pagan philosopher, who had become a convert to Christianity, alludes more than once to the first attempts at a liturgy which the Church used in the administration of the sacraments. He speaks of secret meetings where the psalms were sung, the Scriptures read, and edifying discourses were delivered; he mentions public prayers on behalf of the reigning sovereign, of his ministers, and of the great functionaries of the State; he describes ceremonies, forms of prayer, and religious chants which were used according to certain rites authorised in the Latin Church, amongst which may be distinguished the _Pater_ of the New Testament, that simple and yet sublime and touching invocation of feeble humanity prostrated before the Almighty. [Illustration: Fig. 160.--Symbol of the Trinity, arranged vertically--the Son at the bottom, the Father at the top, and the Holy Ghost in the centre. The Holy Ghost descends from the mouth of the Father and settles on the head of the Son, and proceeds from both. Copied from a French Miniature by Count Horace de Vielcastel (Fourteenth Century).]