in the first instance to last as long as they did. The pise
vaults of the Ninevite palaces could never have stood so well. In spite of
the layers of lead and bitumen which, as Diodorus tells us, were spread
upon their terraces, the summer rains must in time have found their way
into their walls and set up a process of disintegration which could have
but one end. Real brick with good mortar could alone resist such
influences, and those, no doubt, were the materials used in the Babylonian
gardens. If their substructures should ever be found and laid open, we have
little doubt that arches as carefully built as those of the Assyrian ruins
will be brought to light.

The gateways of the town built by Sargon at the foot of his palace mound
were roofed with semicircular vaults.[283] In order to study their
construction more closely, M. Place demolished one of these arches piece by
piece, the one numbered three on his plan.[284] It was already condemned to
destruction by the necessity for carrying off its sculptures.

The total height from pavement to keystone, was twenty-four feet six
inches, from the centre of the keystone to the springing of the arch itself
was eight feet, the total width of the opening, measured at the feet of the
caryatides, was fourteen feet four inches.

The bricks had not been burnt in a kiln but they had been subjected to a
prolonged desiccation. The system of construction was as simple as
possible. The perpendicular side walls passed into the vault without any
preparation, and the arch when complete had no inward projection and no
structural ornament but the inner faces of the carefully placed voussoirs;
as all the bricks were of the same size and shape something more than their
slightly trapezoidal form was required to keep them in place, and a softer
clay was used to bind them together. With the addition of this rude cement
each brick became a long and narrow wedge and determined the curve of the
vault in which it was placed. Some idea of the appearance of this triple
arch may be formed from the illustration we have compiled from M. Thomas's
elevation of an alcove in one of the harem apartments at Khorsabad (Fig.
90). This vault is not in existence, but its component parts were found
among the ruins of Sargon's palace.[285]

[Illustration: FIG. 90.--Interior of a chamber in the harem of Sargon's
palace at Khorsabad; compiled from Place.]

There is one detail in the decoration of these doorways th