The group of medieval and seventeenth-century buildings which forms the subject of this paper lies in the centre of academic Oxford, between the site of the city wall on the north, Exeter College and its garden on the west and south, and the old Schools Quadrangle on the east. It constitutes indeed the heart of the medieval university. In writing to Humphrey, duke of Gloucester, on 14th July 1444 the authorities described the site as eminently suitable for a library because it was somewhat remote from secular noises. In spite of a marked increase in secular noises over the past 500 years in traffic-ridden Oxford, this description remains substantially true today. The buildings, erected then and later, remain in external appearance almost exactly as they are depicted in David Loggan's Oxonia Illustrate. of 1675 (pl. xxvii). They comprise the Divinity School, for which the university was already collecting money and laying the foundations in 1423 ; Duke Humphrey's Library, built over it in the forty-five years following the letter to Duke Humphrey of 1444; Arts End and the Proscholium added at right angles to the east by Sir Thomas Bodley in 1610–12; and Selden End with the Convocation House below, attached similarly to the west in 1637–40. The three upper rooms, Duke Humphrey, Selden End, Arts End, form the core of the ancient buildings of the Bodleian Library: they have been continuously in use for library purposes for between 320 and 360 years.