There existed between the principal abbeys of the same order a spirit of unity, a brotherly zeal to render help and service, and a reciprocal interchange of learned and skilful clerks, who went from one community to another to give it the benefit of their learning or manual ability. It was in this way that the conventual churches and buildings were erected and kept in repair; that they became rich in paintings, statues, and mosaics; that the treasury was filled, and the library founded and maintained. Rupert, a monk of the Abbey of St. Gall (Switzerland), before his elevation to the bishopric of Metz, a learned linguist, poet, and man of letters; Tutilo, his contemporary at St. Gall, a carver, painter, and sculptor; Regino, Abbot of Prüm, an excellent musician, author of a Treatise on Harmony, are of themselves a proof that arts and letters were hidden in the cloisters. At this epoch of barbarism and ignorance, the Church organized what was good, strengthened the shattered foundations of the social edifice, established new monastic institutions and reformed the old, grouped around her the irresolute, lawless, and undisciplined minds (Fig. 245), selling the principles of order and peace in opposition to those of violence and disorder engendered by war. [Illustration: Fig. 246.--Seal of the Abbey of St. Denis, in the Twelfth Century, in the National Archives, Paris.--The saint is clad in his episcopal garb. It is, no doubt, as the apostle of Gaul that the motto gives him the title of archbishop.] Never was the monastic order more numerous or better organized, and at no period, perhaps, were works of mental intelligence cultivated more ardently or successfully in certain privileged monasteries, than at this time. Canterbury, Monte-Cassino, St. Maur, St. Denis (Fig. 246), St. Martin of Tours, St. Gall, Remiremont, Aix-la-Chapelle, Cologne, Trèves, St. Trudon, St. Arnulph, St. Clement, and St. Martin of Metz, the Messinà and the Gorza basilica, were cited as so many foci of light whence radiated in every direction the good doctrines set forth in certain remarkable works of art, as well as in learned literary compositions. [Illustration: Fig. 247.--The Clergy, with the Cross and the Holy Images, going in procession before the Emperor.--From a Miniature taken from a Manuscript of the Fourth Century (Library of M. Ambroise Firmin-Didot).]