That is, on an inner line; the upper row having their supports at the angles of the inscribed octagon, and therefore at a point further removed from the centre of the circle than those of the lower tier, which correspond to the sides of the octagon. Or, simply, “those inside the building,” the upper tier showing in the outside view of the structure, while the lower row would only be visible from the interior. There is apparently a corresponding row of windows above the upper row of arches, carrying the central tower four cubits higher. This at least seems the sense of the clause immediately following.