Such was the nature of the song which resounded about the altars of Roman basilicas and through convent cloisters in the seventh and eighth centuries, and which has remained the sanctioned official speech of the Catholic Church in her ritual functions to the present day. Nowhere did it suffer any material change or addition until it became the basis of a new harmonic art in Northern Europe in the twelfth and thirteenth centuries. The chant according to the Roman use began to extend itself over Europe in connection with the missionary efforts which emanated from Rome from the time of Gregory the Great. Augustine, the emissary of Gregory, who went to England in 597 to convert the Saxons, carried with him the Roman chant. “The band of monks,” says Green, “entered Canterbury bearing before them a silver cross with a picture of Christ, and singing in concert the strains of the litany of their church.”[58] And although the broad-minded Gregory instructed Augustine not to insist upon supplanting with the Roman use the liturgy already employed in the older British churches if such an attempt would create hostility, yet the Roman chant was adopted both at Canterbury and York. The Roman chant was accepted eventually throughout the dominions of the Church as an essential element of the Roman liturgy. Both shared the same struggles and the same triumphs. Familiarity with the church song became an indispensable part of the equipment of every clergyman, monastic and secular. No missionary might go forth from Rome who was not adept in it. Monks made dangerous journeys to Rome from the remotest districts in order to learn it. Every monastery founded in the savage forests of Germany, Gaul, or Britain became at once a singing school, and day and night the holy strains went up in unison with the melodies of the far distant sacred city. The Anglo-Saxon monk Winfrid, afterward known as Boniface, the famous missionary to the Germans, planted the Roman liturgy in Thuringia and Hesse, and devoted untiring efforts to teaching the Gregorian song to his barbarous proselytes. In Spain, Ildefonso, about 600, is enrolled among the zealous promoters of sacred song according to the use of Rome. Most eminent and most successful of all who labored for the exclusive authority of the Roman chant as against the Milanese, Gallican, and other rival forms was Charlemagne, king of the Franks from 768 to 814, whose persistent efforts to implant the Gregorian song in every church and school in his wide dominions was an important detail of his labor in the interest of liturgic uniformity according to the Roman model.