It was probably during this period that the commencement of his friendship with Ambrosius is to be dated. Little is known of this individual. Eusebius[12] states that he had formerly been an adherent of the Valentinian heresy, but had been converted by the arguments and eloquence of Origen to the orthodox faith of the Church. They became intimate friends; and as Ambrose seems to have been possessed of large means, and entertained an unbounded admiration of the learning and abilities of his friend, it was his delight to bear the expenses attending the transcription and publication of the many works which he persuaded him to give to the world. He furnished him “with more than seven amanuenses, who relieved each other at stated times, and with an equal number of transcribers, along with young girls who had been practised in caligraphy,”[13] to make fair copies for publication of the works dictated by Origen. The literary activity of these years must have been prodigious, and probably they were among the happiest which Origen ever enjoyed. Engaged in his favourite studies, surrounded by many friends, adding yearly to his own stores of learning, and enriching the literature of the Church with treatises of the highest value in the department of sacred criticism and exegesis, it is difficult to conceive a condition of things more congenial to the mind of a true scholar. Only one incident of any importance seems to have taken place during these peaceful years,—his visit to Julia Mammæa, the pious mother of Alexander Severus. This noble lady had heard of the fame of Origen, and invited him to visit her at Antioch, sending a military escort to conduct him from Alexandria to the Syrian capital. He remained with her some time, “exhibiting innumerable illustrations of the glory of the Lord, and of the excellence of divine instruction, and then hastened back to his accustomed studies.”[14]