=The Libraries of the Monasteries and Their Arrangements for the Exchange of Books.=--Geoffrey, sub-prior of S. Barbe, in Normandy, is the author of a phrase which has since been frequently quoted. In a letter written in 1170 to Peter Mangot, a monk of Baugercy, in the diocese of Tours, he says: “A monastery (_claustrum_) without a library (_sine armario_) is like a castle (_castrum_) without an armory (_sine armamentario_). Our library is our armory. Thence it is that we bring forth the sentences of the Divine Law like sharp arrows to attack the enemy. Thence we take the armour of righteousness, the helmet of salvation, the shield of faith, and the sword of the spirit, which is the Word of God.”[193] Among the monasteries whose collections of books were noteworthy and whose literary exchanges were not infrequently sufficiently important to be described as a publishing or bookselling trade, may be mentioned the following: Wearmouth and Yarrow, already referred to, the book production in which was active as early as the seventh century; St. Josse-sur-Mer, where, in the ninth century, the Abbot Loup of Ferrières is reported to have kept a depot of books, from which he carried on an active trade with England[194]; Bobbio in Lombardy, the literary treasures in which have been largely preserved in the Ambrosian library; the monastery of Pomposa near Ravenna, whose library, collected by Abbot Jerome in 1093, was said to be finer than any other of the time in Italy; La Chiusa, whose collection rivalled that of Pomposa; Novalese, whose library, at the time of the destruction of the abbey by the Saracens in 905, is reported to have contained no less than 6500 volumes[195]; and Monte Cassino, which under the Abbot Didia, a friend of Gregory VII., possessed a very rich collection. This collection was the result of the researches in Italy of the African Constantine, who, after having passed forty years in the East studying the scientific treatises of Egypt, Persia, Chaldea, and India, had been driven from Carthage by envious rivals. He came to the tomb of S. Benedict, where he assumed the monastic habit, and he endowed his new dwelling with the rich treasures collected in his wanderings.[196] There are also to be mentioned Fulda, whose library at one time surpassed all others in Germany, excepting perhaps that of St. Gall; Croyland, whose library in the eleventh century numbered 3000 volumes; and many others.