Bodley's refurbishment of Duke Humphrey's Library accommodated a large number of readers sitting with immediate access to chained folio volumes in a configuration clearly deriving from the stall libraries of the medieval period. In the early age of print, however, the number of books was multiplying much faster even than the growing number of readers. No sooner had the refurbishment of Duke Humphrey's been completed, therefore, than an overflow space was required which experimented with an entirely different configuration of books and readers.
This new space differed from the old in several striking respects. Most obviously, instead of arranging the books in free-standing stalls running perpendicular to the walls, it stacked the shelves directly against the two main walls running north to south. This meant, second, that height of the bookshelves was not limited to the space between the desk and the height which the people using them could reach: instead the bookshelves could be stacked from floor to ceiling. In order to give access to the upper shelves, third, galleries were installed, accessible by spiral staircases. The books below the galleries were directly accessible to visitors, and this space was reserved for further chained folios, which could be read while sitting on benchings which run parallel to the walls below the galleries. Because access to the upper galleries was restricted, the upper shelves could be stocked with smaller volumes -- mainly quartos and octavos -- for which there was no space in Duke Humphrey's. Finally, since pride of place within the original library was given to the three higher faculties of theology, law and medicine, this annexe was known as Arts End, since it housed books belonging to the sprawling undergraduate arts or philosophy curriculum.
The inspiration for this new arrangement remains unknown. Since nothing of the kind had ever been built in England, it is commonly assumed that it derives from one of Henry Saville's continental travels. But even on the mainland there were very few precedents,* and one of the main features of Arts End remained a unique testimony to this transitional moment in the history of books and libraries: namely, the provision of a traditional library of chained folios beneath the gallery, with benches for reading them incorporated into the fabric of the gallery itself. In the Biblioteca Ambrosiana, constructed in Milan from 1603 onward, two similar tiers of bookshelves line the walls, the upper tier accessible from a gallery; but in this contemporary case books from both tiers can be removed from the shelves and read is desks provided in the middle of the room.
Commentary: Howard Hotson (February 2019).
Further reading. The contrast between the Bodleian and the Ambrosiana can be studied in James W. P. Campbell The Library: A World History, with photographs by Will Pryce (London, 2015), pp. 126-33.