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Of Libraries
97
Does he mean the walls of the room itself? It would seem so, for the bookcases or shelves were not placed against the walls, in which case the ornamentation of the latter would not have been seen, but were set out in the room, just as they are in most public libraries to-day. Glass cut in squares, circles, ovals, and rhomboids was used like marble tiles, to ornament the walls, though oftener the arches and the ceilings. Pliny says in his Natural History, book xxxvi, "Tiles made of earth they transformed into glass and put on the arches; and this is a recent invention." It was, then, still a novelty in the time of Nero and Seneca. Yet Seneca speaks of it as a common
