for books generally had a marketable value--often a high commercial value--notwithstanding the dearth of intelligence and decline of learning. There were times when the possession of a book, especially the Bible, was regarded as a treasure-trove, and the owning of a book by whomsoever written was considered a fact worthy of record by a biographer. So also, toward the close of the Middle Ages when smaller libraries had been established in abbeys and schools, as in France and Spain, manuscript books were borrowed from neighboring libraries and copies were made therefrom to increase many local collections. It was a custom, furthermore, in wide areas for libraries to exchange duplicate copies of books and thus the extension of literature went on even in the "Dark Ages," though with a fluctuating progress. More than this, since much of the literature of the times was written upon the fragile papyrus, a constant renewal of books was made necessary in order to replenish, maintain, and enlarge existing libraries and private collections. This, in the later days, furnished occupation for impecunious students of the universities as well as for slaves, professional scribes, and occupants of the religious houses. But in the intellectual torpor that abounded, and in the pall of almost universal ignorance that overcast the civilized world--under which there were princes and kings who could not even read--it is unreasonable to suppose, notwithstanding the feeble intellectual flickerings that lingered, that there was any very considerable demand for literature during a long period of time, or for a large portion of the "Dark Ages." It was the fact, as says Hallam, the historian of this period, that "a cloud of ignorance overspread the whole face of the Church, hardly broken by a few glimmering lights, who owe much of their distinction to the surrounding darkness." And he portrays at length the gross darkness that enveloped the people, both clergy and laity.[63] In an age when scarcely anybody could write or even read, when learning had well-nigh disappeared under the pall of ignorance, we may easily believe that books were neither extensively made nor highly valued. To again quote from Hallam: "If it be demanded by what cause it happened that a few sparks of ancient learning survived throughout this long winter, we can only ascribe their preservation to the establishment of Christianity. Religion alone made a bridge, as it were, across this chaos and has linked the two periods of ancient and modern civilization." Similar is the testimony of Mr. George H. Putnam: "In the centuries which elapsed between the downfall of the Roman Empire and the invention of printing, the centers of intellectual activities and of scholarly interests were undoubtedly the churches and the monasteries, and it is probable that if it had not been for the educational work done by the priests and monks, and for the interest