Hector and Troy, and the dire wiles of the Greeks never left the mediaeval imagination. A poem of the early tenth century, which bade the watchers on Modena’s walls be vigilant, draws its inspiration from that unfading memory, and for us illustrates what iambics might become when accent had replaced quantity. The lines throughout end in a final rhyming _a_. “O tu, qui servas armis ista moenia, Noli dormire, moneo, sed vigila. Dum Hector vigil extitit in Troia, Non eam cepit fraudulenta Graecia.”[308] And from a scarcely later time, for it also is of the tenth century, rise those verses to Roma, that old “Roma aurea et eterna,” and forever “caput mundi,” sung by pilgrim bands as their eyes caught the first gleam of tower, church, and ruin: “O Roma nobilis, orbis et domina, Cunctarum urbium excellentissima, Roseo martyrum sanguine rubea, Albis et virginum liliis candida: Salutem dicimus tibi per omnia, Te benedicimus: salve per secula.”[309] This verse, which still lifts the heart of whosoever hears or reads it, may close our examples of mediaeval verses descended from metrical forms. It will be noticed that all of them are from the early mediaeval centuries; a circumstance which may be taken as a suggestion of the fact that by far the greater part of the earlier accentual Latin poetry was composed in forms in which accent simply had displaced the antique quantity. III We turn to that other genesis of mediaeval Latin verse, arising not out of antique forms, but rather from the mediaeval need and faculty of song. In the chief instance selected for illustration, this line of evolution took its inception in the exigencies and inspiration of the Alleluia chant or jubilation. During the celebration of the Mass, as the Gradual ended in its last Alleluia, the choir continued chanting the final syllable of that word in cadences of musical exultings. The melody or cadence to which this final _a_ of the Alleluia was chanted, was called the _sequentia_. The words which came to be substituted for its cadenced reiteration were called the _prosa_. By the twelfth century the two terms seem to have been used interchangeably. Thus arose the prose Sequence, so plastic in its capability of being moulded by melody to verse. Its songful qualities lay in the sonorousness of the words and in their syllabic correspondence with the notes of the melody to which they were sung.[310]