Thou art worthy to take the book, and to open the seals thereof (_Rev. 5:9-10_), Worthy is the Lamb that was slain to receive power, and riches, and wisdom, and strength, and honour, and glory, and blessing (_Rev. 5:12-14_), Blessing, and glory, and wisdom, and thanksgiving, and honour, and power, and might, be unto our God for ever and ever (_Rev. 7:12_), Great and marvellous are thy works, Lord God Almighty; just and true are thy ways, thou King of saints (_Rev. 15:3-4_), Alleluia: for the Lord God omnipotent reigneth (_Rev. 19:6_). From the point of view of the evolution of Christian hymns, the hymns in the _Book of Revelation_ are perhaps the most significant in the New Testament because they exhibit varied elements, from Judaism, from Christianity and from the mingling of the two.[14] It is interesting to re-read the New Testament in the search for hymns, but one should remember that the field is controversial. Some commentators would suggest that the entire 13th chapter of _I Corinthians_ is a hymn, beginning, Though I speak with the tongues of men and of angels.[15] A moderate rather than an extreme position, however, upon the identity of hymn sources in the New Testament seems more likely to be productive of a genuine appreciation of the style, subject matter and number of primitive Christian hymns. Traces of poetic improvisation, which is so closely allied to hymnody, must be seriously considered at this point. The art of improvisation belongs to no one age or country. It happens that the Greeks had practiced it for centuries and that illustrations exist from the time of Homer. To the Hellenized orient it was familiar. "The Greeks of Cilicia and of the region about Antioch and Tarsus," as Dr. George Dwight Kellogg reminds us, "seem to have cultivated the art and become famous." He also suggests that the "gift of tongues" refers to this art and that Paul himself possessed the poetic talent in no small degree.[16] It is only natural to assume that, among the early Christians, certain individuals would react to the influence of heightened emotion in outbursts of poetic expression. Passages in the _Book of Acts_ may refer to the use of such hymns, for example, in the case of the Gentiles at Caesarea, who "speak with tongues and magnify God" (_Acts 10:45-46_), or the Ephesians who "spake with tongues, and prophesied" (_Acts 19:6_), or perhaps the disciples on the Day of Pentecost (_Acts 2:4_). Irenaeus, a second century father of the Church and bishop of Lyons, referring to the scene at Pentecost, mentions the singing of a hymn on that occasion.[17] The nature of improvisations is fugitive. They arise from individual inspiration and, even if expressed in familiar phrases, are not remembered or recorded by the singer or hearer. To whatever degree improvisation played a part in early Christian hymnody, to that same degree we lack corresponding literary survivals.