The most noteworthy of the successors of Alcuin in the palace school at Tours was John Scotus Erigena, who in 845 was appointed master by Charles the Bold. The influence of the Irish monk widened the range of study and gave to it an active-minded and speculative tendency that brought about a wide departure from the settled conservatism which had always characterised the teaching of Alcuin. The list of books given to the scribe for copying was increased, and now included, for instance, works of such doubtful orthodoxy as the _Satyricon_ of Martianus Capella, a voluminous compilation constituting a kind of cyclopædia of the seven liberal arts. Its composition dates from about 500.[159] In a treatise, _De Instituto Clericorum_, written in 819 (that is, during the reign of Louis I.), by Rabanus Maurus, who was Abbot of Fulda and later, Archbishop of Mayence, is cited the following regulation: “The canons and the decrees of Pope Zosimus have decided that a clerk proceeding to holy orders shall continue five years among the readers ... and after that shall for four years serve as an acolyte or sub-deacon.” (The Zosimus referred to was Pope for but one year, 417-418.) Rabanus had just before remarked, “_Lectores_ are so called _a legendo_.” He goes on to say that “he who would rightly and properly perform the duty of a reader must be imbued with learning and conversant with books, and must further be instructed in the meaning of words and in the knowledge of the words themselves,” etc.[160] Rabanus follows this with a series of very practical instructions and suggestions for effective education on the part of the readers. These were based upon the treatise on elocution written nearly two hundred years earlier by the learned Bishop Isidore of Seville, and they were again copied three years after the time of Rabanus by Ibo, Bishop of Chartres, in the treatise _De Rebus Ecclesiasticis_. Maitland, to whom I am indebted for this citation, finds cause for indignant criticism of the historian Robertson for the superficial and misleading references made by the historian to the dense ignorance of the Church in the Middle Ages. Maitland suggests that if Robertson had applied for holy orders to the Archbishop of Seville in the seventh century, the Archbishop of Mayence in the ninth, or the Bishop of Chartres in the eleventh, he would have found the examination rather more of a task than he expected. West speaks of Rabanus as “Alcuin’s greatest pupil,” and as intellectually “a greater man than his master.”[161] He wrote a long series of theological and educational treatises.