In one of these sealed vessels, found under the floors, two demotic papyri were discovered (see description by Spiegelberg, p. 46); in others were date cakes, grain, and seeds of different kinds; and in the corner of one of the small outer chambers a batch of forty-seven Ptolemaic coins (p. 44). The fortunate discovery of the papyri and coins, treated hereafter, give data for fixing the period of these vaults to the earlier Ptolemaic times.
With regard to construction, these vault-graves built of mud-brick are of a rectangular longitudinal shape. The side walls, one and a half bricks thick, are from six to ten bricks high, while the end walls are carried up to the height of the crown of the vault. On the inner face of the side walls a ledge is left, half-way up, for a support to carry the vaulted roof (the outer faces are run up as high again to receive the thrust of the vault). The vaulted roof, one brick in thickness, has its rings leaning against the end wall, starting at the foot with first one brick on either side, then two, three, and so on, until the feet of these incomplete rings are far enough out to allow a complete leaning ring to be formed with its crown actually touching the end wall at the top. To this complete ring the bricks of the subsequent rings of the vault are stuck, thus avoiding the force of gravity and enabling the vaulting to be built without the aid of timber centring. This is a method by which a barrel-vault can be made, technically known as a flown-vault, and which is known and used by natives in Egypt at the present day.
For strength and to reduce the thrust, the vault is of parabolic section and not truly semicircular.
Access to these vaulted chambers was sometimes by means of an arched opening in the end wall covered by the vestibule ([Pl. XXXIV]. 2), or, when the latter structure was wanting, by a chimney-like hole at the top of one end of the barrel-vault.
The flat vault bricks (34×16×6 cms.) have grooves on one side to allow the mortar to have a better and firmer grip—a very necessary point for this style of vaulting.