From Britton's Graphical and literary illustrations of Fonthill Abbey, Wiltshire (1823)
Sp Coll RF 996

"Eight piers, composed of clustered demicolumns, with eight tall narrow arches, of eighty feet in height, constitute the first story, or lower division.  Four of these arches, to the east, west, north and south, respectively communicate to the dining-room, the hall, Edward's gallery, and St. Michael's gallery.  The four other spaces, between the piers, have corresponding arches, with recesses in the wall, occupied by tall windows above, of bright stained glass, and scarlet curtains of ample folds beneath: above the arches is an open gallery with a perforated stone balustrade.  This gallery is approached by the great sitting-rooms, over which are corresponding bed-rooms.  this division of the tower is called the nunneries, because the nuns choir, in some female convents, was a gallery placed above the public congregation.  The triforium or gallery between the roof of the aisles and clere story is often, but without any meaning, called the nunneries.  Springing from the capitals of eight lofty columnar shafts, at the angles of the octagon, is a series of diverging groins, or ribs, which support a lanthorn, and another groined roof.  Four sides of this octagonal room are shown in Pl. VII."

(page 43)