It is therefore certain that the cases and seats in the south room date from 1623. It is unfortunately equally certain that we know nothing about the date of those in the west room; and we are therefore unable to say whether the cases in the south room were copied from them in 1623, or whether the reverse process took place at some unknown date. If we adopt the pleasing theory that in the west room we have very early cases, constructed possibly when the library was built, we must still admit that these relics of a remote past have been altered at some subsequent period, so as to be brought into conformity with the cases in the south room; for the cornices and the frames for the titles are precisely similar in the two rooms. The difference between the two sets of cases in the method of chaining, to which attention has been already drawn, may bear on the question of date. As time went on chaining would be modified in the direction of simplicity; and to replace a single central bar by two lateral ones is a step towards this, for under such conditions the addition or removal of a book would entail less displacement. Further, it must be recognised that these cases, whether extremely ancient or comparatively modern, differ in many particulars from those to be met with elsewhere. They are lighter, narrower and more elegant. Again, when the ground-plan of the library is considered (fig. 81) it will be seen that their ends occupy nearly the whole space between a pair of windows. In other examples of the stall-system this is not the case. The only explanation I have to offer for the whole difficulty is the following. The library was constructed for the lectern-system, with wall-spaces not more than 2 ft. wide, and was so fitted up. When books had become numerous the western library was taken in hand, and the lecterns altered into stalls, the single central bar being retained. At the same time, in all probability, the dormers were inserted. It is remarkable that these changes should not be recorded in the accounts, but possibly they were carried out as the result of a special benefaction[336]. In 1623 the stalls which had been placed in the west room, having been found convenient, were copied for the south room. I will in the next place briefly notice the distinctive points of the other examples of the stall-system in Oxford.