Thomas Morton graduated BA from St John's in 1584, MA in 1590, and became a Fellow in 1592. He was ordained in 1594, and embarked upon a career in the Church, beginning as chaplain to the Earl of Huntingdon , and then the the Earl of Rutland, before moving on to the deaneries of Gloucester, and subsequently Winchester. Throughout this period Morton demonstrated his moderate Calvinism, through disputations with local catholics, and the publication of polemical pamphlets against papal authority. In 1612 he also attempted, unsuccessfully, to become master of St John's. From 1616 onwards he held a succession of bishoprics: Chester (until 1619), Coventry and Lichfield (1619-1632), and finally Durham (1632-1641). The latter position took him to the north of England, and his Calvinism fell out of step with the mood at Charles I's court, particularly after the emergence of the Covenanters in Scotland. When Parliament revolted against the King, Morton was one of twelve bishops impeached, although his advanced age saved him from the Tower. After the episcopacy was abolished in 1646 Morton's final years were spent in straitened circumstances, moving between the houses of friends, until his death in 1659.
Morton gave generously to the Library, donating books of his own to the value of three hundred pounds, as well a further hundred pounds for the purchase of books in each of the years 1628, 1634, 1637 and 1639. In total there are five to six hundred items bearing his provenance in the Old Library. In the main these consist of books of canon law, scholastic and doctrinal theology, classics, philology and history. Among them are fifteen incunabula, including two volumes of canon law printed on vellum, both containing Venetian editions printed by Nicolas Jenson in 1476-7, one of which has an illuminated initial. The other books given by Morton range from an early book on the lives of the saints, liberally illustrated with woodcuts (Piero de Natali's Catalogus sanctorum & gestorum eorum, 1506), through works demonstrating early modern Europe's fascination with the might of the Ottoman Empire (Lonicer's Chronicorum Turcicorum tomi III, 1578), and demonology (Rusca's De inferno, et statu daemonum ante mundi exitium, libri quinque, 1621, with diagrams of the location of Hell), to early philological works (Crinesius's Babel, sive, Discursus de confusione linguarum 1629).
The volumes given by Morton, or bought with his monetary donations, bear a variety of provenance markings. Most usually they contain a book label detailing his various donations (second image below). In translation it reads:
The Reverend Father in Christ and Doctor of Divinity Thomas Morton, Doctor of Holy Theology, former scholar and Fellow of this College, Dean of Gloucester and then of Winchester, Bishop firstly of Chester, then of Coventry and Lichfield, and finally of Durham, who, tireless in deserving both of the Church and of this our College, his most beloved nurses (let his deeds speak for themselves), gave 100 pounds to furnish this Library more fully and exquisitely, in the year 1628. And again in 1634 100 pounds, in 1637 100 pounds, in 1639 100 pounds.
Often, although not always, this is in conjunction with one of three gilt armorial bookstamps, one dating from his time as Bishop of Lichfield (third image below), and two very similar ones from his time as Bishop of Durham (fourth and fifth images below). Some volumes simply have an inscription at the top of the title-page.